/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- * vim: set ts=8 sts=4 et sw=4 tw=99: * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ #include "jit/RangeAnalysis.h" #include "mozilla/MathAlgorithms.h" #include "jit/Ion.h" #include "jit/IonAnalysis.h" #include "jit/JitSpewer.h" #include "jit/MIR.h" #include "jit/MIRGenerator.h" #include "jit/MIRGraph.h" #include "js/Conversions.h" #include "vm/ArgumentsObject.h" #include "vm/TypedArrayCommon.h" #include "jsopcodeinlines.h" using namespace js; using namespace js::jit; using mozilla::Abs; using mozilla::CountLeadingZeroes32; using mozilla::NumberEqualsInt32; using mozilla::ExponentComponent; using mozilla::FloorLog2; using mozilla::IsInfinite; using mozilla::IsNaN; using mozilla::IsNegative; using mozilla::IsNegativeZero; using mozilla::NegativeInfinity; using mozilla::PositiveInfinity; using mozilla::Swap; using JS::GenericNaN; using JS::ToInt32; // This algorithm is based on the paper "Eliminating Range Checks Using // Static Single Assignment Form" by Gough and Klaren. // // We associate a range object with each SSA name, and the ranges are consulted // in order to determine whether overflow is possible for arithmetic // computations. // // An important source of range information that requires care to take // advantage of is conditional control flow. Consider the code below: // // if (x < 0) { // y = x + 2000000000; // } else { // if (x < 1000000000) { // y = x * 2; // } else { // y = x - 3000000000; // } // } // // The arithmetic operations in this code cannot overflow, but it is not // sufficient to simply associate each name with a range, since the information // differs between basic blocks. The traditional dataflow approach would be // associate ranges with (name, basic block) pairs. This solution is not // satisfying, since we lose the benefit of SSA form: in SSA form, each // definition has a unique name, so there is no need to track information about // the control flow of the program. // // The approach used here is to add a new form of pseudo operation called a // beta node, which associates range information with a value. These beta // instructions take one argument and additionally have an auxiliary constant // range associated with them. Operationally, beta nodes are just copies, but // the invariant expressed by beta node copies is that the output will fall // inside the range given by the beta node. Gough and Klaeren refer to SSA // extended with these beta nodes as XSA form. The following shows the example // code transformed into XSA form: // // if (x < 0) { // x1 = Beta(x, [INT_MIN, -1]); // y1 = x1 + 2000000000; // } else { // x2 = Beta(x, [0, INT_MAX]); // if (x2 < 1000000000) { // x3 = Beta(x2, [INT_MIN, 999999999]); // y2 = x3*2; // } else { // x4 = Beta(x2, [1000000000, INT_MAX]); // y3 = x4 - 3000000000; // } // y4 = Phi(y2, y3); // } // y = Phi(y1, y4); // // We insert beta nodes for the purposes of range analysis (they might also be // usefully used for other forms of bounds check elimination) and remove them // after range analysis is performed. The remaining compiler phases do not ever // encounter beta nodes. static bool IsDominatedUse(MBasicBlock* block, MUse* use) { MNode* n = use->consumer(); bool isPhi = n->isDefinition() && n->toDefinition()->isPhi(); if (isPhi) { MPhi* phi = n->toDefinition()->toPhi(); return block->dominates(phi->block()->getPredecessor(phi->indexOf(use))); } return block->dominates(n->block()); } static inline void SpewRange(MDefinition* def) { #ifdef JS_JITSPEW if (JitSpewEnabled(JitSpew_Range) && def->type() != MIRType::None && def->range()) { JitSpewHeader(JitSpew_Range); Fprinter& out = JitSpewPrinter(); def->printName(out); out.printf(" has range "); def->range()->dump(out); } #endif } static inline void SpewTruncate(MDefinition* def, MDefinition::TruncateKind kind, bool shouldClone) { #ifdef JS_JITSPEW if (JitSpewEnabled(JitSpew_Range)) { JitSpewHeader(JitSpew_Range); Fprinter& out = JitSpewPrinter(); out.printf("truncating "); def->printName(out); out.printf(" (kind: %s, clone: %d)\n", MDefinition::TruncateKindString(kind), shouldClone); } #endif } TempAllocator& RangeAnalysis::alloc() const { return graph_.alloc(); } void RangeAnalysis::replaceDominatedUsesWith(MDefinition* orig, MDefinition* dom, MBasicBlock* block) { for (MUseIterator i(orig->usesBegin()); i != orig->usesEnd(); ) { MUse* use = *i++; if (use->consumer() != dom && IsDominatedUse(block, use)) use->replaceProducer(dom); } } bool RangeAnalysis::addBetaNodes() { JitSpew(JitSpew_Range, "Adding beta nodes"); for (PostorderIterator i(graph_.poBegin()); i != graph_.poEnd(); i++) { MBasicBlock* block = *i; JitSpew(JitSpew_Range, "Looking at block %d", block->id()); BranchDirection branch_dir; MTest* test = block->immediateDominatorBranch(&branch_dir); if (!test || !test->getOperand(0)->isCompare()) continue; MCompare* compare = test->getOperand(0)->toCompare(); if (!compare->isNumericComparison()) continue; // TODO: support unsigned comparisons if (compare->compareType() == MCompare::Compare_UInt32) continue; MDefinition* left = compare->getOperand(0); MDefinition* right = compare->getOperand(1); double bound; double conservativeLower = NegativeInfinity<double>(); double conservativeUpper = PositiveInfinity<double>(); MDefinition* val = nullptr; JSOp jsop = compare->jsop(); if (branch_dir == FALSE_BRANCH) { jsop = NegateCompareOp(jsop); conservativeLower = GenericNaN(); conservativeUpper = GenericNaN(); } MConstant* leftConst = left->maybeConstantValue(); MConstant* rightConst = right->maybeConstantValue(); if (leftConst && leftConst->isTypeRepresentableAsDouble()) { bound = leftConst->numberToDouble(); val = right; jsop = ReverseCompareOp(jsop); } else if (rightConst && rightConst->isTypeRepresentableAsDouble()) { bound = rightConst->numberToDouble(); val = left; } else if (left->type() == MIRType::Int32 && right->type() == MIRType::Int32) { MDefinition* smaller = nullptr; MDefinition* greater = nullptr; if (jsop == JSOP_LT) { smaller = left; greater = right; } else if (jsop == JSOP_GT) { smaller = right; greater = left; } if (smaller && greater) { if (!alloc().ensureBallast()) return false; MBeta* beta; beta = MBeta::New(alloc(), smaller, Range::NewInt32Range(alloc(), JSVAL_INT_MIN, JSVAL_INT_MAX-1)); block->insertBefore(*block->begin(), beta); replaceDominatedUsesWith(smaller, beta, block); JitSpew(JitSpew_Range, "Adding beta node for smaller %d", smaller->id()); beta = MBeta::New(alloc(), greater, Range::NewInt32Range(alloc(), JSVAL_INT_MIN+1, JSVAL_INT_MAX)); block->insertBefore(*block->begin(), beta); replaceDominatedUsesWith(greater, beta, block); JitSpew(JitSpew_Range, "Adding beta node for greater %d", greater->id()); } continue; } else { continue; } // At this point, one of the operands if the compare is a constant, and // val is the other operand. MOZ_ASSERT(val); Range comp; switch (jsop) { case JSOP_LE: comp.setDouble(conservativeLower, bound); break; case JSOP_LT: // For integers, if x < c, the upper bound of x is c-1. if (val->type() == MIRType::Int32) { int32_t intbound; if (NumberEqualsInt32(bound, &intbound) && SafeSub(intbound, 1, &intbound)) bound = intbound; } comp.setDouble(conservativeLower, bound); // Negative zero is not less than zero. if (bound == 0) comp.refineToExcludeNegativeZero(); break; case JSOP_GE: comp.setDouble(bound, conservativeUpper); break; case JSOP_GT: // For integers, if x > c, the lower bound of x is c+1. if (val->type() == MIRType::Int32) { int32_t intbound; if (NumberEqualsInt32(bound, &intbound) && SafeAdd(intbound, 1, &intbound)) bound = intbound; } comp.setDouble(bound, conservativeUpper); // Negative zero is not greater than zero. if (bound == 0) comp.refineToExcludeNegativeZero(); break; case JSOP_STRICTEQ: // A strict comparison can test for things other than numeric value. if (!compare->isNumericComparison()) continue; // Otherwise fall through to handle JSOP_STRICTEQ the same as JSOP_EQ. MOZ_FALLTHROUGH; case JSOP_EQ: comp.setDouble(bound, bound); break; case JSOP_STRICTNE: // A strict comparison can test for things other than numeric value. if (!compare->isNumericComparison()) continue; // Otherwise fall through to handle JSOP_STRICTNE the same as JSOP_NE. MOZ_FALLTHROUGH; case JSOP_NE: // Negative zero is not not-equal to zero. if (bound == 0) { comp.refineToExcludeNegativeZero(); break; } continue; // well, we could have // [-\inf, bound-1] U [bound+1, \inf] but we only use contiguous ranges. default: continue; } if (JitSpewEnabled(JitSpew_Range)) { JitSpewHeader(JitSpew_Range); Fprinter& out = JitSpewPrinter(); out.printf("Adding beta node for %d with range ", val->id()); comp.dump(out); } if (!alloc().ensureBallast()) return false; MBeta* beta = MBeta::New(alloc(), val, new(alloc()) Range(comp)); block->insertBefore(*block->begin(), beta); replaceDominatedUsesWith(val, beta, block); } return true; } bool RangeAnalysis::removeBetaNodes() { JitSpew(JitSpew_Range, "Removing beta nodes"); for (PostorderIterator i(graph_.poBegin()); i != graph_.poEnd(); i++) { MBasicBlock* block = *i; for (MDefinitionIterator iter(*i); iter; ) { MDefinition* def = *iter++; if (def->isBeta()) { MDefinition* op = def->getOperand(0); JitSpew(JitSpew_Range, "Removing beta node %d for %d", def->id(), op->id()); def->justReplaceAllUsesWith(op); block->discardDef(def); } else { // We only place Beta nodes at the beginning of basic // blocks, so if we see something else, we can move on // to the next block. break; } } } return true; } void SymbolicBound::dump(GenericPrinter& out) const { if (loop) out.printf("[loop] "); sum.dump(out); } void SymbolicBound::dump() const { Fprinter out(stderr); dump(out); out.printf("\n"); out.finish(); } // Test whether the given range's exponent tells us anything that its lower // and upper bound values don't. static bool IsExponentInteresting(const Range* r) { // If it lacks either a lower or upper bound, the exponent is interesting. if (!r->hasInt32Bounds()) return true; // Otherwise if there's no fractional part, the lower and upper bounds, // which are integers, are perfectly precise. if (!r->canHaveFractionalPart()) return false; // Otherwise, if the bounds are conservatively rounded across a power-of-two // boundary, the exponent may imply a tighter range. return FloorLog2(Max(Abs(r->lower()), Abs(r->upper()))) > r->exponent(); } void Range::dump(GenericPrinter& out) const { assertInvariants(); // Floating-point or Integer subset. if (canHaveFractionalPart_) out.printf("F"); else out.printf("I"); out.printf("["); if (!hasInt32LowerBound_) out.printf("?"); else out.printf("%d", lower_); if (symbolicLower_) { out.printf(" {"); symbolicLower_->dump(out); out.printf("}"); } out.printf(", "); if (!hasInt32UpperBound_) out.printf("?"); else out.printf("%d", upper_); if (symbolicUpper_) { out.printf(" {"); symbolicUpper_->dump(out); out.printf("}"); } out.printf("]"); bool includesNaN = max_exponent_ == IncludesInfinityAndNaN; bool includesNegativeInfinity = max_exponent_ >= IncludesInfinity && !hasInt32LowerBound_; bool includesPositiveInfinity = max_exponent_ >= IncludesInfinity && !hasInt32UpperBound_; bool includesNegativeZero = canBeNegativeZero_; if (includesNaN || includesNegativeInfinity || includesPositiveInfinity || includesNegativeZero) { out.printf(" ("); bool first = true; if (includesNaN) { if (first) first = false; else out.printf(" "); out.printf("U NaN"); } if (includesNegativeInfinity) { if (first) first = false; else out.printf(" "); out.printf("U -Infinity"); } if (includesPositiveInfinity) { if (first) first = false; else out.printf(" "); out.printf("U Infinity"); } if (includesNegativeZero) { if (first) first = false; else out.printf(" "); out.printf("U -0"); } out.printf(")"); } if (max_exponent_ < IncludesInfinity && IsExponentInteresting(this)) out.printf(" (< pow(2, %d+1))", max_exponent_); } void Range::dump() const { Fprinter out(stderr); dump(out); out.printf("\n"); out.finish(); } Range* Range::intersect(TempAllocator& alloc, const Range* lhs, const Range* rhs, bool* emptyRange) { *emptyRange = false; if (!lhs && !rhs) return nullptr; if (!lhs) return new(alloc) Range(*rhs); if (!rhs) return new(alloc) Range(*lhs); int32_t newLower = Max(lhs->lower_, rhs->lower_); int32_t newUpper = Min(lhs->upper_, rhs->upper_); // If upper < lower, then we have conflicting constraints. Consider: // // if (x < 0) { // if (x > 0) { // [Some code.] // } // } // // In this case, the block is unreachable. if (newUpper < newLower) { // If both ranges can be NaN, the result can still be NaN. if (!lhs->canBeNaN() || !rhs->canBeNaN()) *emptyRange = true; return nullptr; } bool newHasInt32LowerBound = lhs->hasInt32LowerBound_ || rhs->hasInt32LowerBound_; bool newHasInt32UpperBound = lhs->hasInt32UpperBound_ || rhs->hasInt32UpperBound_; FractionalPartFlag newCanHaveFractionalPart = FractionalPartFlag(lhs->canHaveFractionalPart_ && rhs->canHaveFractionalPart_); NegativeZeroFlag newMayIncludeNegativeZero = NegativeZeroFlag(lhs->canBeNegativeZero_ && rhs->canBeNegativeZero_); uint16_t newExponent = Min(lhs->max_exponent_, rhs->max_exponent_); // NaN is a special value which is neither greater than infinity or less than // negative infinity. When we intersect two ranges like [?, 0] and [0, ?], we // can end up thinking we have both a lower and upper bound, even though NaN // is still possible. In this case, just be conservative, since any case where // we can have NaN is not especially interesting. if (newHasInt32LowerBound && newHasInt32UpperBound && newExponent == IncludesInfinityAndNaN) return nullptr; // If one of the ranges has a fractional part and the other doesn't, it's // possible that we will have computed a newExponent that's more precise // than our newLower and newUpper. This is unusual, so we handle it here // instead of in optimize(). // // For example, consider the range F[0,1.5]. Range analysis represents the // lower and upper bound as integers, so we'd actually have // F[0,2] (< pow(2, 0+1)). In this case, the exponent gives us a slightly // more precise upper bound than the integer upper bound. // // When intersecting such a range with an integer range, the fractional part // of the range is dropped. The max exponent of 0 remains valid, so the // upper bound needs to be adjusted to 1. // // When intersecting F[0,2] (< pow(2, 0+1)) with a range like F[2,4], // the naive intersection is I[2,2], but since the max exponent tells us // that the value is always less than 2, the intersection is actually empty. if (lhs->canHaveFractionalPart() != rhs->canHaveFractionalPart() || (lhs->canHaveFractionalPart() && newHasInt32LowerBound && newHasInt32UpperBound && newLower == newUpper)) { refineInt32BoundsByExponent(newExponent, &newLower, &newHasInt32LowerBound, &newUpper, &newHasInt32UpperBound); // If we're intersecting two ranges that don't overlap, this could also // push the bounds past each other, since the actual intersection is // the empty set. if (newLower > newUpper) { *emptyRange = true; return nullptr; } } return new(alloc) Range(newLower, newHasInt32LowerBound, newUpper, newHasInt32UpperBound, newCanHaveFractionalPart, newMayIncludeNegativeZero, newExponent); } void Range::unionWith(const Range* other) { int32_t newLower = Min(lower_, other->lower_); int32_t newUpper = Max(upper_, other->upper_); bool newHasInt32LowerBound = hasInt32LowerBound_ && other->hasInt32LowerBound_; bool newHasInt32UpperBound = hasInt32UpperBound_ && other->hasInt32UpperBound_; FractionalPartFlag newCanHaveFractionalPart = FractionalPartFlag(canHaveFractionalPart_ || other->canHaveFractionalPart_); NegativeZeroFlag newMayIncludeNegativeZero = NegativeZeroFlag(canBeNegativeZero_ || other->canBeNegativeZero_); uint16_t newExponent = Max(max_exponent_, other->max_exponent_); rawInitialize(newLower, newHasInt32LowerBound, newUpper, newHasInt32UpperBound, newCanHaveFractionalPart, newMayIncludeNegativeZero, newExponent); } Range::Range(const MDefinition* def) : symbolicLower_(nullptr), symbolicUpper_(nullptr) { if (const Range* other = def->range()) { // The instruction has range information; use it. *this = *other; // Simulate the effect of converting the value to its type. // Note: we cannot clamp here, since ranges aren't allowed to shrink // and truncation can increase range again. So doing wrapAround to // mimick a possible truncation. switch (def->type()) { case MIRType::Int32: // MToInt32 cannot truncate. So we can safely clamp. if (def->isToInt32()) clampToInt32(); else wrapAroundToInt32(); break; case MIRType::Boolean: wrapAroundToBoolean(); break; case MIRType::None: MOZ_CRASH("Asking for the range of an instruction with no value"); default: break; } } else { // Otherwise just use type information. We can trust the type here // because we don't care what value the instruction actually produces, // but what value we might get after we get past the bailouts. switch (def->type()) { case MIRType::Int32: setInt32(JSVAL_INT_MIN, JSVAL_INT_MAX); break; case MIRType::Boolean: setInt32(0, 1); break; case MIRType::None: MOZ_CRASH("Asking for the range of an instruction with no value"); default: setUnknown(); break; } } // As a special case, MUrsh is permitted to claim a result type of // MIRType::Int32 while actually returning values in [0,UINT32_MAX] without // bailouts. If range analysis hasn't ruled out values in // (INT32_MAX,UINT32_MAX], set the range to be conservatively correct for // use as either a uint32 or an int32. if (!hasInt32UpperBound() && def->isUrsh() && def->toUrsh()->bailoutsDisabled() && def->type() != MIRType::Int64) { lower_ = INT32_MIN; } assertInvariants(); } static uint16_t ExponentImpliedByDouble(double d) { // Handle the special values. if (IsNaN(d)) return Range::IncludesInfinityAndNaN; if (IsInfinite(d)) return Range::IncludesInfinity; // Otherwise take the exponent part and clamp it at zero, since the Range // class doesn't track fractional ranges. return uint16_t(Max(int_fast16_t(0), ExponentComponent(d))); } void Range::setDouble(double l, double h) { MOZ_ASSERT(!(l > h)); // Infer lower_, upper_, hasInt32LowerBound_, and hasInt32UpperBound_. if (l >= INT32_MIN && l <= INT32_MAX) { lower_ = int32_t(::floor(l)); hasInt32LowerBound_ = true; } else if (l >= INT32_MAX) { lower_ = INT32_MAX; hasInt32LowerBound_ = true; } else { lower_ = INT32_MIN; hasInt32LowerBound_ = false; } if (h >= INT32_MIN && h <= INT32_MAX) { upper_ = int32_t(::ceil(h)); hasInt32UpperBound_ = true; } else if (h <= INT32_MIN) { upper_ = INT32_MIN; hasInt32UpperBound_ = true; } else { upper_ = INT32_MAX; hasInt32UpperBound_ = false; } // Infer max_exponent_. uint16_t lExp = ExponentImpliedByDouble(l); uint16_t hExp = ExponentImpliedByDouble(h); max_exponent_ = Max(lExp, hExp); canHaveFractionalPart_ = ExcludesFractionalParts; canBeNegativeZero_ = ExcludesNegativeZero; // Infer the canHaveFractionalPart_ setting. We can have a // fractional part if the range crosses through the neighborhood of zero. We // won't have a fractional value if the value is always beyond the point at // which double precision can't represent fractional values. uint16_t minExp = Min(lExp, hExp); bool includesNegative = IsNaN(l) || l < 0; bool includesPositive = IsNaN(h) || h > 0; bool crossesZero = includesNegative && includesPositive; if (crossesZero || minExp < MaxTruncatableExponent) canHaveFractionalPart_ = IncludesFractionalParts; // Infer the canBeNegativeZero_ setting. We can have a negative zero if // either bound is zero. if (!(l > 0) && !(h < 0)) canBeNegativeZero_ = IncludesNegativeZero; optimize(); } void Range::setDoubleSingleton(double d) { setDouble(d, d); // The above setDouble call is for comparisons, and treats negative zero // as equal to zero. We're aiming for a minimum range, so we can clear the // negative zero flag if the value isn't actually negative zero. if (!IsNegativeZero(d)) canBeNegativeZero_ = ExcludesNegativeZero; assertInvariants(); } static inline bool MissingAnyInt32Bounds(const Range* lhs, const Range* rhs) { return !lhs->hasInt32Bounds() || !rhs->hasInt32Bounds(); } Range* Range::add(TempAllocator& alloc, const Range* lhs, const Range* rhs) { int64_t l = (int64_t) lhs->lower_ + (int64_t) rhs->lower_; if (!lhs->hasInt32LowerBound() || !rhs->hasInt32LowerBound()) l = NoInt32LowerBound; int64_t h = (int64_t) lhs->upper_ + (int64_t) rhs->upper_; if (!lhs->hasInt32UpperBound() || !rhs->hasInt32UpperBound()) h = NoInt32UpperBound; // The exponent is at most one greater than the greater of the operands' // exponents, except for NaN and infinity cases. uint16_t e = Max(lhs->max_exponent_, rhs->max_exponent_); if (e <= Range::MaxFiniteExponent) ++e; // Infinity + -Infinity is NaN. if (lhs->canBeInfiniteOrNaN() && rhs->canBeInfiniteOrNaN()) e = Range::IncludesInfinityAndNaN; return new(alloc) Range(l, h, FractionalPartFlag(lhs->canHaveFractionalPart() || rhs->canHaveFractionalPart()), NegativeZeroFlag(lhs->canBeNegativeZero() && rhs->canBeNegativeZero()), e); } Range* Range::sub(TempAllocator& alloc, const Range* lhs, const Range* rhs) { int64_t l = (int64_t) lhs->lower_ - (int64_t) rhs->upper_; if (!lhs->hasInt32LowerBound() || !rhs->hasInt32UpperBound()) l = NoInt32LowerBound; int64_t h = (int64_t) lhs->upper_ - (int64_t) rhs->lower_; if (!lhs->hasInt32UpperBound() || !rhs->hasInt32LowerBound()) h = NoInt32UpperBound; // The exponent is at most one greater than the greater of the operands' // exponents, except for NaN and infinity cases. uint16_t e = Max(lhs->max_exponent_, rhs->max_exponent_); if (e <= Range::MaxFiniteExponent) ++e; // Infinity - Infinity is NaN. if (lhs->canBeInfiniteOrNaN() && rhs->canBeInfiniteOrNaN()) e = Range::IncludesInfinityAndNaN; return new(alloc) Range(l, h, FractionalPartFlag(lhs->canHaveFractionalPart() || rhs->canHaveFractionalPart()), NegativeZeroFlag(lhs->canBeNegativeZero() && rhs->canBeZero()), e); } Range* Range::and_(TempAllocator& alloc, const Range* lhs, const Range* rhs) { MOZ_ASSERT(lhs->isInt32()); MOZ_ASSERT(rhs->isInt32()); // If both numbers can be negative, result can be negative in the whole range if (lhs->lower() < 0 && rhs->lower() < 0) return Range::NewInt32Range(alloc, INT32_MIN, Max(lhs->upper(), rhs->upper())); // Only one of both numbers can be negative. // - result can't be negative // - Upper bound is minimum of both upper range, int32_t lower = 0; int32_t upper = Min(lhs->upper(), rhs->upper()); // EXCEPT when upper bound of non negative number is max value, // because negative value can return the whole max value. // -1 & 5 = 5 if (lhs->lower() < 0) upper = rhs->upper(); if (rhs->lower() < 0) upper = lhs->upper(); return Range::NewInt32Range(alloc, lower, upper); } Range* Range::or_(TempAllocator& alloc, const Range* lhs, const Range* rhs) { MOZ_ASSERT(lhs->isInt32()); MOZ_ASSERT(rhs->isInt32()); // When one operand is always 0 or always -1, it's a special case where we // can compute a fully precise result. Handling these up front also // protects the code below from calling CountLeadingZeroes32 with a zero // operand or from shifting an int32_t by 32. if (lhs->lower() == lhs->upper()) { if (lhs->lower() == 0) return new(alloc) Range(*rhs); if (lhs->lower() == -1) return new(alloc) Range(*lhs); } if (rhs->lower() == rhs->upper()) { if (rhs->lower() == 0) return new(alloc) Range(*lhs); if (rhs->lower() == -1) return new(alloc) Range(*rhs); } // The code below uses CountLeadingZeroes32, which has undefined behavior // if its operand is 0. We rely on the code above to protect it. MOZ_ASSERT_IF(lhs->lower() >= 0, lhs->upper() != 0); MOZ_ASSERT_IF(rhs->lower() >= 0, rhs->upper() != 0); MOZ_ASSERT_IF(lhs->upper() < 0, lhs->lower() != -1); MOZ_ASSERT_IF(rhs->upper() < 0, rhs->lower() != -1); int32_t lower = INT32_MIN; int32_t upper = INT32_MAX; if (lhs->lower() >= 0 && rhs->lower() >= 0) { // Both operands are non-negative, so the result won't be less than either. lower = Max(lhs->lower(), rhs->lower()); // The result will have leading zeros where both operands have leading zeros. // CountLeadingZeroes32 of a non-negative int32 will at least be 1 to account // for the bit of sign. upper = int32_t(UINT32_MAX >> Min(CountLeadingZeroes32(lhs->upper()), CountLeadingZeroes32(rhs->upper()))); } else { // The result will have leading ones where either operand has leading ones. if (lhs->upper() < 0) { unsigned leadingOnes = CountLeadingZeroes32(~lhs->lower()); lower = Max(lower, ~int32_t(UINT32_MAX >> leadingOnes)); upper = -1; } if (rhs->upper() < 0) { unsigned leadingOnes = CountLeadingZeroes32(~rhs->lower()); lower = Max(lower, ~int32_t(UINT32_MAX >> leadingOnes)); upper = -1; } } return Range::NewInt32Range(alloc, lower, upper); } Range* Range::xor_(TempAllocator& alloc, const Range* lhs, const Range* rhs) { MOZ_ASSERT(lhs->isInt32()); MOZ_ASSERT(rhs->isInt32()); int32_t lhsLower = lhs->lower(); int32_t lhsUpper = lhs->upper(); int32_t rhsLower = rhs->lower(); int32_t rhsUpper = rhs->upper(); bool invertAfter = false; // If either operand is negative, bitwise-negate it, and arrange to negate // the result; ~((~x)^y) == x^y. If both are negative the negations on the // result cancel each other out; effectively this is (~x)^(~y) == x^y. // These transformations reduce the number of cases we have to handle below. if (lhsUpper < 0) { lhsLower = ~lhsLower; lhsUpper = ~lhsUpper; Swap(lhsLower, lhsUpper); invertAfter = !invertAfter; } if (rhsUpper < 0) { rhsLower = ~rhsLower; rhsUpper = ~rhsUpper; Swap(rhsLower, rhsUpper); invertAfter = !invertAfter; } // Handle cases where lhs or rhs is always zero specially, because they're // easy cases where we can be perfectly precise, and because it protects the // CountLeadingZeroes32 calls below from seeing 0 operands, which would be // undefined behavior. int32_t lower = INT32_MIN; int32_t upper = INT32_MAX; if (lhsLower == 0 && lhsUpper == 0) { upper = rhsUpper; lower = rhsLower; } else if (rhsLower == 0 && rhsUpper == 0) { upper = lhsUpper; lower = lhsLower; } else if (lhsLower >= 0 && rhsLower >= 0) { // Both operands are non-negative. The result will be non-negative. lower = 0; // To compute the upper value, take each operand's upper value and // set all bits that don't correspond to leading zero bits in the // other to one. For each one, this gives an upper bound for the // result, so we can take the minimum between the two. unsigned lhsLeadingZeros = CountLeadingZeroes32(lhsUpper); unsigned rhsLeadingZeros = CountLeadingZeroes32(rhsUpper); upper = Min(rhsUpper | int32_t(UINT32_MAX >> lhsLeadingZeros), lhsUpper | int32_t(UINT32_MAX >> rhsLeadingZeros)); } // If we bitwise-negated one (but not both) of the operands above, apply the // bitwise-negate to the result, completing ~((~x)^y) == x^y. if (invertAfter) { lower = ~lower; upper = ~upper; Swap(lower, upper); } return Range::NewInt32Range(alloc, lower, upper); } Range* Range::not_(TempAllocator& alloc, const Range* op) { MOZ_ASSERT(op->isInt32()); return Range::NewInt32Range(alloc, ~op->upper(), ~op->lower()); } Range* Range::mul(TempAllocator& alloc, const Range* lhs, const Range* rhs) { FractionalPartFlag newCanHaveFractionalPart = FractionalPartFlag(lhs->canHaveFractionalPart_ || rhs->canHaveFractionalPart_); NegativeZeroFlag newMayIncludeNegativeZero = NegativeZeroFlag((lhs->canHaveSignBitSet() && rhs->canBeFiniteNonNegative()) || (rhs->canHaveSignBitSet() && lhs->canBeFiniteNonNegative())); uint16_t exponent; if (!lhs->canBeInfiniteOrNaN() && !rhs->canBeInfiniteOrNaN()) { // Two finite values. exponent = lhs->numBits() + rhs->numBits() - 1; if (exponent > Range::MaxFiniteExponent) exponent = Range::IncludesInfinity; } else if (!lhs->canBeNaN() && !rhs->canBeNaN() && !(lhs->canBeZero() && rhs->canBeInfiniteOrNaN()) && !(rhs->canBeZero() && lhs->canBeInfiniteOrNaN())) { // Two values that multiplied together won't produce a NaN. exponent = Range::IncludesInfinity; } else { // Could be anything. exponent = Range::IncludesInfinityAndNaN; } if (MissingAnyInt32Bounds(lhs, rhs)) return new(alloc) Range(NoInt32LowerBound, NoInt32UpperBound, newCanHaveFractionalPart, newMayIncludeNegativeZero, exponent); int64_t a = (int64_t)lhs->lower() * (int64_t)rhs->lower(); int64_t b = (int64_t)lhs->lower() * (int64_t)rhs->upper(); int64_t c = (int64_t)lhs->upper() * (int64_t)rhs->lower(); int64_t d = (int64_t)lhs->upper() * (int64_t)rhs->upper(); return new(alloc) Range( Min( Min(a, b), Min(c, d) ), Max( Max(a, b), Max(c, d) ), newCanHaveFractionalPart, newMayIncludeNegativeZero, exponent); } Range* Range::lsh(TempAllocator& alloc, const Range* lhs, int32_t c) { MOZ_ASSERT(lhs->isInt32()); int32_t shift = c & 0x1f; // If the shift doesn't loose bits or shift bits into the sign bit, we // can simply compute the correct range by shifting. if ((int32_t)((uint32_t)lhs->lower() << shift << 1 >> shift >> 1) == lhs->lower() && (int32_t)((uint32_t)lhs->upper() << shift << 1 >> shift >> 1) == lhs->upper()) { return Range::NewInt32Range(alloc, uint32_t(lhs->lower()) << shift, uint32_t(lhs->upper()) << shift); } return Range::NewInt32Range(alloc, INT32_MIN, INT32_MAX); } Range* Range::rsh(TempAllocator& alloc, const Range* lhs, int32_t c) { MOZ_ASSERT(lhs->isInt32()); int32_t shift = c & 0x1f; return Range::NewInt32Range(alloc, lhs->lower() >> shift, lhs->upper() >> shift); } Range* Range::ursh(TempAllocator& alloc, const Range* lhs, int32_t c) { // ursh's left operand is uint32, not int32, but for range analysis we // currently approximate it as int32. We assume here that the range has // already been adjusted accordingly by our callers. MOZ_ASSERT(lhs->isInt32()); int32_t shift = c & 0x1f; // If the value is always non-negative or always negative, we can simply // compute the correct range by shifting. if (lhs->isFiniteNonNegative() || lhs->isFiniteNegative()) { return Range::NewUInt32Range(alloc, uint32_t(lhs->lower()) >> shift, uint32_t(lhs->upper()) >> shift); } // Otherwise return the most general range after the shift. return Range::NewUInt32Range(alloc, 0, UINT32_MAX >> shift); } Range* Range::lsh(TempAllocator& alloc, const Range* lhs, const Range* rhs) { MOZ_ASSERT(lhs->isInt32()); MOZ_ASSERT(rhs->isInt32()); return Range::NewInt32Range(alloc, INT32_MIN, INT32_MAX); } Range* Range::rsh(TempAllocator& alloc, const Range* lhs, const Range* rhs) { MOZ_ASSERT(lhs->isInt32()); MOZ_ASSERT(rhs->isInt32()); // Canonicalize the shift range to 0 to 31. int32_t shiftLower = rhs->lower(); int32_t shiftUpper = rhs->upper(); if ((int64_t(shiftUpper) - int64_t(shiftLower)) >= 31) { shiftLower = 0; shiftUpper = 31; } else { shiftLower &= 0x1f; shiftUpper &= 0x1f; if (shiftLower > shiftUpper) { shiftLower = 0; shiftUpper = 31; } } MOZ_ASSERT(shiftLower >= 0 && shiftUpper <= 31); // The lhs bounds are signed, thus the minimum is either the lower bound // shift by the smallest shift if negative or the lower bound shifted by the // biggest shift otherwise. And the opposite for the maximum. int32_t lhsLower = lhs->lower(); int32_t min = lhsLower < 0 ? lhsLower >> shiftLower : lhsLower >> shiftUpper; int32_t lhsUpper = lhs->upper(); int32_t max = lhsUpper >= 0 ? lhsUpper >> shiftLower : lhsUpper >> shiftUpper; return Range::NewInt32Range(alloc, min, max); } Range* Range::ursh(TempAllocator& alloc, const Range* lhs, const Range* rhs) { // ursh's left operand is uint32, not int32, but for range analysis we // currently approximate it as int32. We assume here that the range has // already been adjusted accordingly by our callers. MOZ_ASSERT(lhs->isInt32()); MOZ_ASSERT(rhs->isInt32()); return Range::NewUInt32Range(alloc, 0, lhs->isFiniteNonNegative() ? lhs->upper() : UINT32_MAX); } Range* Range::abs(TempAllocator& alloc, const Range* op) { int32_t l = op->lower_; int32_t u = op->upper_; FractionalPartFlag canHaveFractionalPart = op->canHaveFractionalPart_; // Abs never produces a negative zero. NegativeZeroFlag canBeNegativeZero = ExcludesNegativeZero; return new(alloc) Range(Max(Max(int32_t(0), l), u == INT32_MIN ? INT32_MAX : -u), true, Max(Max(int32_t(0), u), l == INT32_MIN ? INT32_MAX : -l), op->hasInt32Bounds() && l != INT32_MIN, canHaveFractionalPart, canBeNegativeZero, op->max_exponent_); } Range* Range::min(TempAllocator& alloc, const Range* lhs, const Range* rhs) { // If either operand is NaN, the result is NaN. if (lhs->canBeNaN() || rhs->canBeNaN()) return nullptr; FractionalPartFlag newCanHaveFractionalPart = FractionalPartFlag(lhs->canHaveFractionalPart_ || rhs->canHaveFractionalPart_); NegativeZeroFlag newMayIncludeNegativeZero = NegativeZeroFlag(lhs->canBeNegativeZero_ || rhs->canBeNegativeZero_); return new(alloc) Range(Min(lhs->lower_, rhs->lower_), lhs->hasInt32LowerBound_ && rhs->hasInt32LowerBound_, Min(lhs->upper_, rhs->upper_), lhs->hasInt32UpperBound_ || rhs->hasInt32UpperBound_, newCanHaveFractionalPart, newMayIncludeNegativeZero, Max(lhs->max_exponent_, rhs->max_exponent_)); } Range* Range::max(TempAllocator& alloc, const Range* lhs, const Range* rhs) { // If either operand is NaN, the result is NaN. if (lhs->canBeNaN() || rhs->canBeNaN()) return nullptr; FractionalPartFlag newCanHaveFractionalPart = FractionalPartFlag(lhs->canHaveFractionalPart_ || rhs->canHaveFractionalPart_); NegativeZeroFlag newMayIncludeNegativeZero = NegativeZeroFlag(lhs->canBeNegativeZero_ || rhs->canBeNegativeZero_); return new(alloc) Range(Max(lhs->lower_, rhs->lower_), lhs->hasInt32LowerBound_ || rhs->hasInt32LowerBound_, Max(lhs->upper_, rhs->upper_), lhs->hasInt32UpperBound_ && rhs->hasInt32UpperBound_, newCanHaveFractionalPart, newMayIncludeNegativeZero, Max(lhs->max_exponent_, rhs->max_exponent_)); } Range* Range::floor(TempAllocator& alloc, const Range* op) { Range* copy = new(alloc) Range(*op); // Decrement lower bound of copy range if op have a factional part and lower // bound is Int32 defined. Also we avoid to decrement when op have a // fractional part but lower_ >= JSVAL_INT_MAX. if (op->canHaveFractionalPart() && op->hasInt32LowerBound()) copy->setLowerInit(int64_t(copy->lower_) - 1); // Also refine max_exponent_ because floor may have decremented int value // If we've got int32 defined bounds, just deduce it using defined bounds. // But, if we don't have those, value's max_exponent_ may have changed. // Because we're looking to maintain an over estimation, if we can, // we increment it. if(copy->hasInt32Bounds()) copy->max_exponent_ = copy->exponentImpliedByInt32Bounds(); else if(copy->max_exponent_ < MaxFiniteExponent) copy->max_exponent_++; copy->canHaveFractionalPart_ = ExcludesFractionalParts; copy->assertInvariants(); return copy; } Range* Range::ceil(TempAllocator& alloc, const Range* op) { Range* copy = new(alloc) Range(*op); // We need to refine max_exponent_ because ceil may have incremented the int value. // If we have got int32 bounds defined, just deduce it using the defined bounds. // Else we can just increment its value, // as we are looking to maintain an over estimation. if (copy->hasInt32Bounds()) copy->max_exponent_ = copy->exponentImpliedByInt32Bounds(); else if (copy->max_exponent_ < MaxFiniteExponent) copy->max_exponent_++; copy->canHaveFractionalPart_ = ExcludesFractionalParts; copy->assertInvariants(); return copy; } Range* Range::sign(TempAllocator& alloc, const Range* op) { if (op->canBeNaN()) return nullptr; return new(alloc) Range(Max(Min(op->lower_, 1), -1), Max(Min(op->upper_, 1), -1), Range::ExcludesFractionalParts, NegativeZeroFlag(op->canBeNegativeZero()), 0); } Range* Range::NaNToZero(TempAllocator& alloc, const Range *op) { Range* copy = new(alloc) Range(*op); if (copy->canBeNaN()) { copy->max_exponent_ = Range::IncludesInfinity; if (!copy->canBeZero()) { Range zero; zero.setDoubleSingleton(0); copy->unionWith(&zero); } } copy->refineToExcludeNegativeZero(); return copy; } bool Range::negativeZeroMul(const Range* lhs, const Range* rhs) { // The result can only be negative zero if both sides are finite and they // have differing signs. return (lhs->canHaveSignBitSet() && rhs->canBeFiniteNonNegative()) || (rhs->canHaveSignBitSet() && lhs->canBeFiniteNonNegative()); } bool Range::update(const Range* other) { bool changed = lower_ != other->lower_ || hasInt32LowerBound_ != other->hasInt32LowerBound_ || upper_ != other->upper_ || hasInt32UpperBound_ != other->hasInt32UpperBound_ || canHaveFractionalPart_ != other->canHaveFractionalPart_ || canBeNegativeZero_ != other->canBeNegativeZero_ || max_exponent_ != other->max_exponent_; if (changed) { lower_ = other->lower_; hasInt32LowerBound_ = other->hasInt32LowerBound_; upper_ = other->upper_; hasInt32UpperBound_ = other->hasInt32UpperBound_; canHaveFractionalPart_ = other->canHaveFractionalPart_; canBeNegativeZero_ = other->canBeNegativeZero_; max_exponent_ = other->max_exponent_; assertInvariants(); } return changed; } /////////////////////////////////////////////////////////////////////////////// // Range Computation for MIR Nodes /////////////////////////////////////////////////////////////////////////////// void MPhi::computeRange(TempAllocator& alloc) { if (type() != MIRType::Int32 && type() != MIRType::Double) return; Range* range = nullptr; for (size_t i = 0, e = numOperands(); i < e; i++) { if (getOperand(i)->block()->unreachable()) { JitSpew(JitSpew_Range, "Ignoring unreachable input %d", getOperand(i)->id()); continue; } // Peek at the pre-bailout range so we can take a short-cut; if any of // the operands has an unknown range, this phi has an unknown range. if (!getOperand(i)->range()) return; Range input(getOperand(i)); if (range) range->unionWith(&input); else range = new(alloc) Range(input); } setRange(range); } void MBeta::computeRange(TempAllocator& alloc) { bool emptyRange = false; Range opRange(getOperand(0)); Range* range = Range::intersect(alloc, &opRange, comparison_, &emptyRange); if (emptyRange) { JitSpew(JitSpew_Range, "Marking block for inst %d unreachable", id()); block()->setUnreachableUnchecked(); } else { setRange(range); } } void MConstant::computeRange(TempAllocator& alloc) { if (isTypeRepresentableAsDouble()) { double d = numberToDouble(); setRange(Range::NewDoubleSingletonRange(alloc, d)); } else if (type() == MIRType::Boolean) { bool b = toBoolean(); setRange(Range::NewInt32Range(alloc, b, b)); } } void MCharCodeAt::computeRange(TempAllocator& alloc) { // ECMA 262 says that the integer will be non-negative and at most 65535. setRange(Range::NewInt32Range(alloc, 0, 65535)); } void MClampToUint8::computeRange(TempAllocator& alloc) { setRange(Range::NewUInt32Range(alloc, 0, 255)); } void MBitAnd::computeRange(TempAllocator& alloc) { if (specialization_ == MIRType::Int64) return; Range left(getOperand(0)); Range right(getOperand(1)); left.wrapAroundToInt32(); right.wrapAroundToInt32(); setRange(Range::and_(alloc, &left, &right)); } void MBitOr::computeRange(TempAllocator& alloc) { if (specialization_ == MIRType::Int64) return; Range left(getOperand(0)); Range right(getOperand(1)); left.wrapAroundToInt32(); right.wrapAroundToInt32(); setRange(Range::or_(alloc, &left, &right)); } void MBitXor::computeRange(TempAllocator& alloc) { if (specialization_ == MIRType::Int64) return; Range left(getOperand(0)); Range right(getOperand(1)); left.wrapAroundToInt32(); right.wrapAroundToInt32(); setRange(Range::xor_(alloc, &left, &right)); } void MBitNot::computeRange(TempAllocator& alloc) { Range op(getOperand(0)); op.wrapAroundToInt32(); setRange(Range::not_(alloc, &op)); } void MLsh::computeRange(TempAllocator& alloc) { if (specialization_ == MIRType::Int64) return; Range left(getOperand(0)); Range right(getOperand(1)); left.wrapAroundToInt32(); MConstant* rhsConst = getOperand(1)->maybeConstantValue(); if (rhsConst && rhsConst->type() == MIRType::Int32) { int32_t c = rhsConst->toInt32(); setRange(Range::lsh(alloc, &left, c)); return; } right.wrapAroundToShiftCount(); setRange(Range::lsh(alloc, &left, &right)); } void MRsh::computeRange(TempAllocator& alloc) { if (specialization_ == MIRType::Int64) return; Range left(getOperand(0)); Range right(getOperand(1)); left.wrapAroundToInt32(); MConstant* rhsConst = getOperand(1)->maybeConstantValue(); if (rhsConst && rhsConst->type() == MIRType::Int32) { int32_t c = rhsConst->toInt32(); setRange(Range::rsh(alloc, &left, c)); return; } right.wrapAroundToShiftCount(); setRange(Range::rsh(alloc, &left, &right)); } void MUrsh::computeRange(TempAllocator& alloc) { if (specialization_ == MIRType::Int64) return; Range left(getOperand(0)); Range right(getOperand(1)); // ursh can be thought of as converting its left operand to uint32, or it // can be thought of as converting its left operand to int32, and then // reinterpreting the int32 bits as a uint32 value. Both approaches yield // the same result. Since we lack support for full uint32 ranges, we use // the second interpretation, though it does cause us to be conservative. left.wrapAroundToInt32(); right.wrapAroundToShiftCount(); MConstant* rhsConst = getOperand(1)->maybeConstantValue(); if (rhsConst && rhsConst->type() == MIRType::Int32) { int32_t c = rhsConst->toInt32(); setRange(Range::ursh(alloc, &left, c)); } else { setRange(Range::ursh(alloc, &left, &right)); } MOZ_ASSERT(range()->lower() >= 0); } void MAbs::computeRange(TempAllocator& alloc) { if (specialization_ != MIRType::Int32 && specialization_ != MIRType::Double) return; Range other(getOperand(0)); Range* next = Range::abs(alloc, &other); if (implicitTruncate_) next->wrapAroundToInt32(); setRange(next); } void MFloor::computeRange(TempAllocator& alloc) { Range other(getOperand(0)); setRange(Range::floor(alloc, &other)); } void MCeil::computeRange(TempAllocator& alloc) { Range other(getOperand(0)); setRange(Range::ceil(alloc, &other)); } void MClz::computeRange(TempAllocator& alloc) { if (type() != MIRType::Int32) return; setRange(Range::NewUInt32Range(alloc, 0, 32)); } void MCtz::computeRange(TempAllocator& alloc) { if (type() != MIRType::Int32) return; setRange(Range::NewUInt32Range(alloc, 0, 32)); } void MPopcnt::computeRange(TempAllocator& alloc) { if (type() != MIRType::Int32) return; setRange(Range::NewUInt32Range(alloc, 0, 32)); } void MMinMax::computeRange(TempAllocator& alloc) { if (specialization_ != MIRType::Int32 && specialization_ != MIRType::Double) return; Range left(getOperand(0)); Range right(getOperand(1)); setRange(isMax() ? Range::max(alloc, &left, &right) : Range::min(alloc, &left, &right)); } void MAdd::computeRange(TempAllocator& alloc) { if (specialization() != MIRType::Int32 && specialization() != MIRType::Double) return; Range left(getOperand(0)); Range right(getOperand(1)); Range* next = Range::add(alloc, &left, &right); if (isTruncated()) next->wrapAroundToInt32(); setRange(next); } void MSub::computeRange(TempAllocator& alloc) { if (specialization() != MIRType::Int32 && specialization() != MIRType::Double) return; Range left(getOperand(0)); Range right(getOperand(1)); Range* next = Range::sub(alloc, &left, &right); if (isTruncated()) next->wrapAroundToInt32(); setRange(next); } void MMul::computeRange(TempAllocator& alloc) { if (specialization() != MIRType::Int32 && specialization() != MIRType::Double) return; Range left(getOperand(0)); Range right(getOperand(1)); if (canBeNegativeZero()) canBeNegativeZero_ = Range::negativeZeroMul(&left, &right); Range* next = Range::mul(alloc, &left, &right); if (!next->canBeNegativeZero()) canBeNegativeZero_ = false; // Truncated multiplications could overflow in both directions if (isTruncated()) next->wrapAroundToInt32(); setRange(next); } void MMod::computeRange(TempAllocator& alloc) { if (specialization() != MIRType::Int32 && specialization() != MIRType::Double) return; Range lhs(getOperand(0)); Range rhs(getOperand(1)); // If either operand is a NaN, the result is NaN. This also conservatively // handles Infinity cases. if (!lhs.hasInt32Bounds() || !rhs.hasInt32Bounds()) return; // If RHS can be zero, the result can be NaN. if (rhs.lower() <= 0 && rhs.upper() >= 0) return; // If both operands are non-negative integers, we can optimize this to an // unsigned mod. if (specialization() == MIRType::Int32 && rhs.lower() > 0) { bool hasDoubles = lhs.lower() < 0 || lhs.canHaveFractionalPart() || rhs.canHaveFractionalPart(); // It is not possible to check that lhs.lower() >= 0, since the range // of a ursh with rhs a 0 constant is wrapped around the int32 range in // Range::Range(). However, IsUint32Type() will only return true for // nodes that lie in the range [0, UINT32_MAX]. bool hasUint32s = IsUint32Type(getOperand(0)) && getOperand(1)->type() == MIRType::Int32 && (IsUint32Type(getOperand(1)) || getOperand(1)->isConstant()); if (!hasDoubles || hasUint32s) unsigned_ = true; } // For unsigned mod, we have to convert both operands to unsigned. // Note that we handled the case of a zero rhs above. if (unsigned_) { // The result of an unsigned mod will never be unsigned-greater than // either operand. uint32_t lhsBound = Max<uint32_t>(lhs.lower(), lhs.upper()); uint32_t rhsBound = Max<uint32_t>(rhs.lower(), rhs.upper()); // If either range crosses through -1 as a signed value, it could be // the maximum unsigned value when interpreted as unsigned. If the range // doesn't include -1, then the simple max value we computed above is // correct. if (lhs.lower() <= -1 && lhs.upper() >= -1) lhsBound = UINT32_MAX; if (rhs.lower() <= -1 && rhs.upper() >= -1) rhsBound = UINT32_MAX; // The result will never be equal to the rhs, and we shouldn't have // any rounding to worry about. MOZ_ASSERT(!lhs.canHaveFractionalPart() && !rhs.canHaveFractionalPart()); --rhsBound; // This gives us two upper bounds, so we can take the best one. setRange(Range::NewUInt32Range(alloc, 0, Min(lhsBound, rhsBound))); return; } // Math.abs(lhs % rhs) == Math.abs(lhs) % Math.abs(rhs). // First, the absolute value of the result will always be less than the // absolute value of rhs. (And if rhs is zero, the result is NaN). int64_t a = Abs<int64_t>(rhs.lower()); int64_t b = Abs<int64_t>(rhs.upper()); if (a == 0 && b == 0) return; int64_t rhsAbsBound = Max(a, b); // If the value is known to be integer, less-than abs(rhs) is equivalent // to less-than-or-equal abs(rhs)-1. This is important for being able to // say that the result of x%256 is an 8-bit unsigned number. if (!lhs.canHaveFractionalPart() && !rhs.canHaveFractionalPart()) --rhsAbsBound; // Next, the absolute value of the result will never be greater than the // absolute value of lhs. int64_t lhsAbsBound = Max(Abs<int64_t>(lhs.lower()), Abs<int64_t>(lhs.upper())); // This gives us two upper bounds, so we can take the best one. int64_t absBound = Min(lhsAbsBound, rhsAbsBound); // Now consider the sign of the result. // If lhs is non-negative, the result will be non-negative. // If lhs is non-positive, the result will be non-positive. int64_t lower = lhs.lower() >= 0 ? 0 : -absBound; int64_t upper = lhs.upper() <= 0 ? 0 : absBound; Range::FractionalPartFlag newCanHaveFractionalPart = Range::FractionalPartFlag(lhs.canHaveFractionalPart() || rhs.canHaveFractionalPart()); // If the lhs can have the sign bit set and we can return a zero, it'll be a // negative zero. Range::NegativeZeroFlag newMayIncludeNegativeZero = Range::NegativeZeroFlag(lhs.canHaveSignBitSet()); setRange(new(alloc) Range(lower, upper, newCanHaveFractionalPart, newMayIncludeNegativeZero, Min(lhs.exponent(), rhs.exponent()))); } void MDiv::computeRange(TempAllocator& alloc) { if (specialization() != MIRType::Int32 && specialization() != MIRType::Double) return; Range lhs(getOperand(0)); Range rhs(getOperand(1)); // If either operand is a NaN, the result is NaN. This also conservatively // handles Infinity cases. if (!lhs.hasInt32Bounds() || !rhs.hasInt32Bounds()) return; // Something simple for now: When dividing by a positive rhs, the result // won't be further from zero than lhs. if (lhs.lower() >= 0 && rhs.lower() >= 1) { setRange(new(alloc) Range(0, lhs.upper(), Range::IncludesFractionalParts, Range::IncludesNegativeZero, lhs.exponent())); } else if (unsigned_ && rhs.lower() >= 1) { // We shouldn't set the unsigned flag if the inputs can have // fractional parts. MOZ_ASSERT(!lhs.canHaveFractionalPart() && !rhs.canHaveFractionalPart()); // We shouldn't set the unsigned flag if the inputs can be // negative zero. MOZ_ASSERT(!lhs.canBeNegativeZero() && !rhs.canBeNegativeZero()); // Unsigned division by a non-zero rhs will return a uint32 value. setRange(Range::NewUInt32Range(alloc, 0, UINT32_MAX)); } } void MSqrt::computeRange(TempAllocator& alloc) { Range input(getOperand(0)); // If either operand is a NaN, the result is NaN. This also conservatively // handles Infinity cases. if (!input.hasInt32Bounds()) return; // Sqrt of a negative non-zero value is NaN. if (input.lower() < 0) return; // Something simple for now: When taking the sqrt of a positive value, the // result won't be further from zero than the input. // And, sqrt of an integer may have a fractional part. setRange(new(alloc) Range(0, input.upper(), Range::IncludesFractionalParts, input.canBeNegativeZero(), input.exponent())); } void MToDouble::computeRange(TempAllocator& alloc) { setRange(new(alloc) Range(getOperand(0))); } void MToFloat32::computeRange(TempAllocator& alloc) { } void MTruncateToInt32::computeRange(TempAllocator& alloc) { Range* output = new(alloc) Range(getOperand(0)); output->wrapAroundToInt32(); setRange(output); } void MToInt32::computeRange(TempAllocator& alloc) { // No clamping since this computes the range *before* bailouts. setRange(new(alloc) Range(getOperand(0))); } void MLimitedTruncate::computeRange(TempAllocator& alloc) { Range* output = new(alloc) Range(input()); setRange(output); } void MFilterTypeSet::computeRange(TempAllocator& alloc) { setRange(new(alloc) Range(getOperand(0))); } static Range* GetTypedArrayRange(TempAllocator& alloc, Scalar::Type type) { switch (type) { case Scalar::Uint8Clamped: case Scalar::Uint8: return Range::NewUInt32Range(alloc, 0, UINT8_MAX); case Scalar::Uint16: return Range::NewUInt32Range(alloc, 0, UINT16_MAX); case Scalar::Uint32: return Range::NewUInt32Range(alloc, 0, UINT32_MAX); case Scalar::Int8: return Range::NewInt32Range(alloc, INT8_MIN, INT8_MAX); case Scalar::Int16: return Range::NewInt32Range(alloc, INT16_MIN, INT16_MAX); case Scalar::Int32: return Range::NewInt32Range(alloc, INT32_MIN, INT32_MAX); case Scalar::Int64: case Scalar::Float32: case Scalar::Float64: case Scalar::Float32x4: case Scalar::Int8x16: case Scalar::Int16x8: case Scalar::Int32x4: case Scalar::MaxTypedArrayViewType: break; } return nullptr; } void MLoadUnboxedScalar::computeRange(TempAllocator& alloc) { // We have an Int32 type and if this is a UInt32 load it may produce a value // outside of our range, but we have a bailout to handle those cases. setRange(GetTypedArrayRange(alloc, readType())); } void MLoadTypedArrayElementStatic::computeRange(TempAllocator& alloc) { // We don't currently use MLoadTypedArrayElementStatic for uint32, so we // don't have to worry about it returning a value outside our type. MOZ_ASSERT(someTypedArray_->as<TypedArrayObject>().type() != Scalar::Uint32); setRange(GetTypedArrayRange(alloc, someTypedArray_->as<TypedArrayObject>().type())); } void MArrayLength::computeRange(TempAllocator& alloc) { // Array lengths can go up to UINT32_MAX, but we only create MArrayLength // nodes when the value is known to be int32 (see the // OBJECT_FLAG_LENGTH_OVERFLOW flag). setRange(Range::NewUInt32Range(alloc, 0, INT32_MAX)); } void MInitializedLength::computeRange(TempAllocator& alloc) { setRange(Range::NewUInt32Range(alloc, 0, NativeObject::MAX_DENSE_ELEMENTS_COUNT)); } void MTypedArrayLength::computeRange(TempAllocator& alloc) { setRange(Range::NewUInt32Range(alloc, 0, INT32_MAX)); } void MStringLength::computeRange(TempAllocator& alloc) { static_assert(JSString::MAX_LENGTH <= UINT32_MAX, "NewUInt32Range requires a uint32 value"); setRange(Range::NewUInt32Range(alloc, 0, JSString::MAX_LENGTH)); } void MArgumentsLength::computeRange(TempAllocator& alloc) { // This is is a conservative upper bound on what |TooManyActualArguments| // checks. If exceeded, Ion will not be entered in the first place. static_assert(ARGS_LENGTH_MAX <= UINT32_MAX, "NewUInt32Range requires a uint32 value"); setRange(Range::NewUInt32Range(alloc, 0, ARGS_LENGTH_MAX)); } void MBoundsCheck::computeRange(TempAllocator& alloc) { // Just transfer the incoming index range to the output. The length() is // also interesting, but it is handled as a bailout check, and we're // computing a pre-bailout range here. setRange(new(alloc) Range(index())); } void MArrayPush::computeRange(TempAllocator& alloc) { // MArrayPush returns the new array length. setRange(Range::NewUInt32Range(alloc, 0, UINT32_MAX)); } void MMathFunction::computeRange(TempAllocator& alloc) { Range opRange(getOperand(0)); switch (function()) { case Sin: case Cos: if (!opRange.canBeInfiniteOrNaN()) setRange(Range::NewDoubleRange(alloc, -1.0, 1.0)); break; case Sign: setRange(Range::sign(alloc, &opRange)); break; default: break; } } void MRandom::computeRange(TempAllocator& alloc) { Range* r = Range::NewDoubleRange(alloc, 0.0, 1.0); // Random never returns negative zero. r->refineToExcludeNegativeZero(); setRange(r); } void MNaNToZero::computeRange(TempAllocator& alloc) { Range other(input()); setRange(Range::NaNToZero(alloc, &other)); } /////////////////////////////////////////////////////////////////////////////// // Range Analysis /////////////////////////////////////////////////////////////////////////////// bool RangeAnalysis::analyzeLoop(MBasicBlock* header) { MOZ_ASSERT(header->hasUniqueBackedge()); // Try to compute an upper bound on the number of times the loop backedge // will be taken. Look for tests that dominate the backedge and which have // an edge leaving the loop body. MBasicBlock* backedge = header->backedge(); // Ignore trivial infinite loops. if (backedge == header) return true; bool canOsr; size_t numBlocks = MarkLoopBlocks(graph_, header, &canOsr); // Ignore broken loops. if (numBlocks == 0) return true; LoopIterationBound* iterationBound = nullptr; MBasicBlock* block = backedge; do { BranchDirection direction; MTest* branch = block->immediateDominatorBranch(&direction); if (block == block->immediateDominator()) break; block = block->immediateDominator(); if (branch) { direction = NegateBranchDirection(direction); MBasicBlock* otherBlock = branch->branchSuccessor(direction); if (!otherBlock->isMarked()) { if (!alloc().ensureBallast()) return false; iterationBound = analyzeLoopIterationCount(header, branch, direction); if (iterationBound) break; } } } while (block != header); if (!iterationBound) { UnmarkLoopBlocks(graph_, header); return true; } if (!loopIterationBounds.append(iterationBound)) return false; #ifdef DEBUG if (JitSpewEnabled(JitSpew_Range)) { Sprinter sp(GetJitContext()->cx); if (!sp.init()) return false; iterationBound->boundSum.dump(sp); JitSpew(JitSpew_Range, "computed symbolic bound on backedges: %s", sp.string()); } #endif // Try to compute symbolic bounds for the phi nodes at the head of this // loop, expressed in terms of the iteration bound just computed. for (MPhiIterator iter(header->phisBegin()); iter != header->phisEnd(); iter++) analyzeLoopPhi(header, iterationBound, *iter); if (!mir->compilingWasm()) { // Try to hoist any bounds checks from the loop using symbolic bounds. Vector<MBoundsCheck*, 0, JitAllocPolicy> hoistedChecks(alloc()); for (ReversePostorderIterator iter(graph_.rpoBegin(header)); iter != graph_.rpoEnd(); iter++) { MBasicBlock* block = *iter; if (!block->isMarked()) continue; for (MDefinitionIterator iter(block); iter; iter++) { MDefinition* def = *iter; if (def->isBoundsCheck() && def->isMovable()) { if (!alloc().ensureBallast()) return false; if (tryHoistBoundsCheck(header, def->toBoundsCheck())) { if (!hoistedChecks.append(def->toBoundsCheck())) return false; } } } } // Note: replace all uses of the original bounds check with the // actual index. This is usually done during bounds check elimination, // but in this case it's safe to do it here since the load/store is // definitely not loop-invariant, so we will never move it before // one of the bounds checks we just added. for (size_t i = 0; i < hoistedChecks.length(); i++) { MBoundsCheck* ins = hoistedChecks[i]; ins->replaceAllUsesWith(ins->index()); ins->block()->discard(ins); } } UnmarkLoopBlocks(graph_, header); return true; } // Unbox beta nodes in order to hoist instruction properly, and not be limited // by the beta nodes which are added after each branch. static inline MDefinition* DefinitionOrBetaInputDefinition(MDefinition* ins) { while (ins->isBeta()) ins = ins->toBeta()->input(); return ins; } LoopIterationBound* RangeAnalysis::analyzeLoopIterationCount(MBasicBlock* header, MTest* test, BranchDirection direction) { SimpleLinearSum lhs(nullptr, 0); MDefinition* rhs; bool lessEqual; if (!ExtractLinearInequality(test, direction, &lhs, &rhs, &lessEqual)) return nullptr; // Ensure the rhs is a loop invariant term. if (rhs && rhs->block()->isMarked()) { if (lhs.term && lhs.term->block()->isMarked()) return nullptr; MDefinition* temp = lhs.term; lhs.term = rhs; rhs = temp; if (!SafeSub(0, lhs.constant, &lhs.constant)) return nullptr; lessEqual = !lessEqual; } MOZ_ASSERT_IF(rhs, !rhs->block()->isMarked()); // Ensure the lhs is a phi node from the start of the loop body. if (!lhs.term || !lhs.term->isPhi() || lhs.term->block() != header) return nullptr; // Check that the value of the lhs changes by a constant amount with each // loop iteration. This requires that the lhs be written in every loop // iteration with a value that is a constant difference from its value at // the start of the iteration. if (lhs.term->toPhi()->numOperands() != 2) return nullptr; // The first operand of the phi should be the lhs' value at the start of // the first executed iteration, and not a value written which could // replace the second operand below during the middle of execution. MDefinition* lhsInitial = lhs.term->toPhi()->getLoopPredecessorOperand(); if (lhsInitial->block()->isMarked()) return nullptr; // The second operand of the phi should be a value written by an add/sub // in every loop iteration, i.e. in a block which dominates the backedge. MDefinition* lhsWrite = DefinitionOrBetaInputDefinition(lhs.term->toPhi()->getLoopBackedgeOperand()); if (!lhsWrite->isAdd() && !lhsWrite->isSub()) return nullptr; if (!lhsWrite->block()->isMarked()) return nullptr; MBasicBlock* bb = header->backedge(); for (; bb != lhsWrite->block() && bb != header; bb = bb->immediateDominator()) {} if (bb != lhsWrite->block()) return nullptr; SimpleLinearSum lhsModified = ExtractLinearSum(lhsWrite); // Check that the value of the lhs at the backedge is of the form // 'old(lhs) + N'. We can be sure that old(lhs) is the value at the start // of the iteration, and not that written to lhs in a previous iteration, // as such a previous value could not appear directly in the addition: // it could not be stored in lhs as the lhs add/sub executes in every // iteration, and if it were stored in another variable its use here would // be as an operand to a phi node for that variable. if (lhsModified.term != lhs.term) return nullptr; LinearSum iterationBound(alloc()); LinearSum currentIteration(alloc()); if (lhsModified.constant == 1 && !lessEqual) { // The value of lhs is 'initial(lhs) + iterCount' and this will end // execution of the loop if 'lhs + lhsN >= rhs'. Thus, an upper bound // on the number of backedges executed is: // // initial(lhs) + iterCount + lhsN == rhs // iterCount == rhsN - initial(lhs) - lhsN if (rhs) { if (!iterationBound.add(rhs, 1)) return nullptr; } if (!iterationBound.add(lhsInitial, -1)) return nullptr; int32_t lhsConstant; if (!SafeSub(0, lhs.constant, &lhsConstant)) return nullptr; if (!iterationBound.add(lhsConstant)) return nullptr; if (!currentIteration.add(lhs.term, 1)) return nullptr; if (!currentIteration.add(lhsInitial, -1)) return nullptr; } else if (lhsModified.constant == -1 && lessEqual) { // The value of lhs is 'initial(lhs) - iterCount'. Similar to the above // case, an upper bound on the number of backedges executed is: // // initial(lhs) - iterCount + lhsN == rhs // iterCount == initial(lhs) - rhs + lhsN if (!iterationBound.add(lhsInitial, 1)) return nullptr; if (rhs) { if (!iterationBound.add(rhs, -1)) return nullptr; } if (!iterationBound.add(lhs.constant)) return nullptr; if (!currentIteration.add(lhsInitial, 1)) return nullptr; if (!currentIteration.add(lhs.term, -1)) return nullptr; } else { return nullptr; } return new(alloc()) LoopIterationBound(header, test, iterationBound, currentIteration); } void RangeAnalysis::analyzeLoopPhi(MBasicBlock* header, LoopIterationBound* loopBound, MPhi* phi) { // Given a bound on the number of backedges taken, compute an upper and // lower bound for a phi node that may change by a constant amount each // iteration. Unlike for the case when computing the iteration bound // itself, the phi does not need to change the same amount every iteration, // but is required to change at most N and be either nondecreasing or // nonincreasing. MOZ_ASSERT(phi->numOperands() == 2); MDefinition* initial = phi->getLoopPredecessorOperand(); if (initial->block()->isMarked()) return; SimpleLinearSum modified = ExtractLinearSum(phi->getLoopBackedgeOperand(), MathSpace::Infinite); if (modified.term != phi || modified.constant == 0) return; if (!phi->range()) phi->setRange(new(alloc()) Range(phi)); LinearSum initialSum(alloc()); if (!initialSum.add(initial, 1)) return; // The phi may change by N each iteration, and is either nondecreasing or // nonincreasing. initial(phi) is either a lower or upper bound for the // phi, and initial(phi) + loopBound * N is either an upper or lower bound, // at all points within the loop, provided that loopBound >= 0. // // We are more interested, however, in the bound for phi at points // dominated by the loop bound's test; if the test dominates e.g. a bounds // check we want to hoist from the loop, using the value of the phi at the // head of the loop for this will usually be too imprecise to hoist the // check. These points will execute only if the backedge executes at least // one more time (as the test passed and the test dominates the backedge), // so we know both that loopBound >= 1 and that the phi's value has changed // at most loopBound - 1 times. Thus, another upper or lower bound for the // phi is initial(phi) + (loopBound - 1) * N, without requiring us to // ensure that loopBound >= 0. LinearSum limitSum(loopBound->boundSum); if (!limitSum.multiply(modified.constant) || !limitSum.add(initialSum)) return; int32_t negativeConstant; if (!SafeSub(0, modified.constant, &negativeConstant) || !limitSum.add(negativeConstant)) return; Range* initRange = initial->range(); if (modified.constant > 0) { if (initRange && initRange->hasInt32LowerBound()) phi->range()->refineLower(initRange->lower()); phi->range()->setSymbolicLower(SymbolicBound::New(alloc(), nullptr, initialSum)); phi->range()->setSymbolicUpper(SymbolicBound::New(alloc(), loopBound, limitSum)); } else { if (initRange && initRange->hasInt32UpperBound()) phi->range()->refineUpper(initRange->upper()); phi->range()->setSymbolicUpper(SymbolicBound::New(alloc(), nullptr, initialSum)); phi->range()->setSymbolicLower(SymbolicBound::New(alloc(), loopBound, limitSum)); } JitSpew(JitSpew_Range, "added symbolic range on %d", phi->id()); SpewRange(phi); } // Whether bound is valid at the specified bounds check instruction in a loop, // and may be used to hoist ins. static inline bool SymbolicBoundIsValid(MBasicBlock* header, MBoundsCheck* ins, const SymbolicBound* bound) { if (!bound->loop) return true; if (ins->block() == header) return false; MBasicBlock* bb = ins->block()->immediateDominator(); while (bb != header && bb != bound->loop->test->block()) bb = bb->immediateDominator(); return bb == bound->loop->test->block(); } bool RangeAnalysis::tryHoistBoundsCheck(MBasicBlock* header, MBoundsCheck* ins) { // The bounds check's length must be loop invariant. MDefinition *length = DefinitionOrBetaInputDefinition(ins->length()); if (length->block()->isMarked()) return false; // The bounds check's index should not be loop invariant (else we would // already have hoisted it during LICM). SimpleLinearSum index = ExtractLinearSum(ins->index()); if (!index.term || !index.term->block()->isMarked()) return false; // Check for a symbolic lower and upper bound on the index. If either // condition depends on an iteration bound for the loop, only hoist if // the bounds check is dominated by the iteration bound's test. if (!index.term->range()) return false; const SymbolicBound* lower = index.term->range()->symbolicLower(); if (!lower || !SymbolicBoundIsValid(header, ins, lower)) return false; const SymbolicBound* upper = index.term->range()->symbolicUpper(); if (!upper || !SymbolicBoundIsValid(header, ins, upper)) return false; MBasicBlock* preLoop = header->loopPredecessor(); MOZ_ASSERT(!preLoop->isMarked()); MDefinition* lowerTerm = ConvertLinearSum(alloc(), preLoop, lower->sum); if (!lowerTerm) return false; MDefinition* upperTerm = ConvertLinearSum(alloc(), preLoop, upper->sum); if (!upperTerm) return false; // We are checking that index + indexConstant >= 0, and know that // index >= lowerTerm + lowerConstant. Thus, check that: // // lowerTerm + lowerConstant + indexConstant >= 0 // lowerTerm >= -lowerConstant - indexConstant int32_t lowerConstant = 0; if (!SafeSub(lowerConstant, index.constant, &lowerConstant)) return false; if (!SafeSub(lowerConstant, lower->sum.constant(), &lowerConstant)) return false; // We are checking that index < boundsLength, and know that // index <= upperTerm + upperConstant. Thus, check that: // // upperTerm + upperConstant < boundsLength int32_t upperConstant = index.constant; if (!SafeAdd(upper->sum.constant(), upperConstant, &upperConstant)) return false; // Hoist the loop invariant lower bounds checks. MBoundsCheckLower* lowerCheck = MBoundsCheckLower::New(alloc(), lowerTerm); lowerCheck->setMinimum(lowerConstant); lowerCheck->computeRange(alloc()); lowerCheck->collectRangeInfoPreTrunc(); preLoop->insertBefore(preLoop->lastIns(), lowerCheck); // Hoist the loop invariant upper bounds checks. if (upperTerm != length || upperConstant >= 0) { MBoundsCheck* upperCheck = MBoundsCheck::New(alloc(), upperTerm, length); upperCheck->setMinimum(upperConstant); upperCheck->setMaximum(upperConstant); upperCheck->computeRange(alloc()); upperCheck->collectRangeInfoPreTrunc(); preLoop->insertBefore(preLoop->lastIns(), upperCheck); } return true; } bool RangeAnalysis::analyze() { JitSpew(JitSpew_Range, "Doing range propagation"); for (ReversePostorderIterator iter(graph_.rpoBegin()); iter != graph_.rpoEnd(); iter++) { MBasicBlock* block = *iter; // No blocks are supposed to be unreachable, except when we have an OSR // block, in which case the Value Numbering phase add fixup blocks which // are unreachable. MOZ_ASSERT(!block->unreachable() || graph_.osrBlock()); // If the block's immediate dominator is unreachable, the block is // unreachable. Iterating in RPO, we'll always see the immediate // dominator before the block. if (block->immediateDominator()->unreachable()) { block->setUnreachableUnchecked(); continue; } for (MDefinitionIterator iter(block); iter; iter++) { MDefinition* def = *iter; if (!alloc().ensureBallast()) return false; def->computeRange(alloc()); JitSpew(JitSpew_Range, "computing range on %d", def->id()); SpewRange(def); } // Beta node range analysis may have marked this block unreachable. If // so, it's no longer interesting to continue processing it. if (block->unreachable()) continue; if (block->isLoopHeader()) { if (!analyzeLoop(block)) return false; } // First pass at collecting range info - while the beta nodes are still // around and before truncation. for (MInstructionIterator iter(block->begin()); iter != block->end(); iter++) iter->collectRangeInfoPreTrunc(); } return true; } bool RangeAnalysis::addRangeAssertions() { if (!JitOptions.checkRangeAnalysis) return true; // Check the computed range for this instruction, if the option is set. Note // that this code is quite invasive; it adds numerous additional // instructions for each MInstruction with a computed range, and it uses // registers, so it also affects register allocation. for (ReversePostorderIterator iter(graph_.rpoBegin()); iter != graph_.rpoEnd(); iter++) { MBasicBlock* block = *iter; // Do not add assertions in unreachable blocks. if (block->unreachable()) continue; for (MDefinitionIterator iter(block); iter; iter++) { MDefinition* ins = *iter; // Perform range checking for all numeric and numeric-like types. if (!IsNumberType(ins->type()) && ins->type() != MIRType::Boolean && ins->type() != MIRType::Value) { continue; } // MIsNoIter is fused with the MTest that follows it and emitted as // LIsNoIterAndBranch. Skip it to avoid complicating MIsNoIter // lowering. if (ins->isIsNoIter()) continue; Range r(ins); MOZ_ASSERT_IF(ins->type() == MIRType::Int64, r.isUnknown()); // Don't insert assertions if there's nothing interesting to assert. if (r.isUnknown() || (ins->type() == MIRType::Int32 && r.isUnknownInt32())) continue; // Don't add a use to an instruction that is recovered on bailout. if (ins->isRecoveredOnBailout()) continue; if (!alloc().ensureBallast()) return false; MAssertRange* guard = MAssertRange::New(alloc(), ins, new(alloc()) Range(r)); // Beta nodes and interrupt checks are required to be located at the // beginnings of basic blocks, so we must insert range assertions // after any such instructions. MInstruction* insertAt = nullptr; if (block->graph().osrBlock() == block) insertAt = ins->toInstruction(); else insertAt = block->safeInsertTop(ins); if (insertAt == *iter) block->insertAfter(insertAt, guard); else block->insertBefore(insertAt, guard); } } return true; } /////////////////////////////////////////////////////////////////////////////// // Range based Truncation /////////////////////////////////////////////////////////////////////////////// void Range::clampToInt32() { if (isInt32()) return; int32_t l = hasInt32LowerBound() ? lower() : JSVAL_INT_MIN; int32_t h = hasInt32UpperBound() ? upper() : JSVAL_INT_MAX; setInt32(l, h); } void Range::wrapAroundToInt32() { if (!hasInt32Bounds()) { setInt32(JSVAL_INT_MIN, JSVAL_INT_MAX); } else if (canHaveFractionalPart()) { // Clearing the fractional field may provide an opportunity to refine // lower_ or upper_. canHaveFractionalPart_ = ExcludesFractionalParts; canBeNegativeZero_ = ExcludesNegativeZero; refineInt32BoundsByExponent(max_exponent_, &lower_, &hasInt32LowerBound_, &upper_, &hasInt32UpperBound_); assertInvariants(); } else { // If nothing else, we can clear the negative zero flag. canBeNegativeZero_ = ExcludesNegativeZero; } MOZ_ASSERT(isInt32()); } void Range::wrapAroundToShiftCount() { wrapAroundToInt32(); if (lower() < 0 || upper() >= 32) setInt32(0, 31); } void Range::wrapAroundToBoolean() { wrapAroundToInt32(); if (!isBoolean()) setInt32(0, 1); MOZ_ASSERT(isBoolean()); } bool MDefinition::needTruncation(TruncateKind kind) { // No procedure defined for truncating this instruction. return false; } void MDefinition::truncate() { MOZ_CRASH("No procedure defined for truncating this instruction."); } bool MConstant::needTruncation(TruncateKind kind) { return IsFloatingPointType(type()); } void MConstant::truncate() { MOZ_ASSERT(needTruncation(Truncate)); // Truncate the double to int, since all uses truncates it. int32_t res = ToInt32(numberToDouble()); payload_.asBits = 0; payload_.i32 = res; setResultType(MIRType::Int32); if (range()) range()->setInt32(res, res); } bool MPhi::needTruncation(TruncateKind kind) { if (type() == MIRType::Double || type() == MIRType::Int32) { truncateKind_ = kind; return true; } return false; } void MPhi::truncate() { setResultType(MIRType::Int32); if (truncateKind_ >= IndirectTruncate && range()) range()->wrapAroundToInt32(); } bool MAdd::needTruncation(TruncateKind kind) { // Remember analysis, needed for fallible checks. setTruncateKind(kind); return type() == MIRType::Double || type() == MIRType::Int32; } void MAdd::truncate() { MOZ_ASSERT(needTruncation(truncateKind())); specialization_ = MIRType::Int32; setResultType(MIRType::Int32); if (truncateKind() >= IndirectTruncate && range()) range()->wrapAroundToInt32(); } bool MSub::needTruncation(TruncateKind kind) { // Remember analysis, needed for fallible checks. setTruncateKind(kind); return type() == MIRType::Double || type() == MIRType::Int32; } void MSub::truncate() { MOZ_ASSERT(needTruncation(truncateKind())); specialization_ = MIRType::Int32; setResultType(MIRType::Int32); if (truncateKind() >= IndirectTruncate && range()) range()->wrapAroundToInt32(); } bool MMul::needTruncation(TruncateKind kind) { // Remember analysis, needed for fallible checks. setTruncateKind(kind); return type() == MIRType::Double || type() == MIRType::Int32; } void MMul::truncate() { MOZ_ASSERT(needTruncation(truncateKind())); specialization_ = MIRType::Int32; setResultType(MIRType::Int32); if (truncateKind() >= IndirectTruncate) { setCanBeNegativeZero(false); if (range()) range()->wrapAroundToInt32(); } } bool MDiv::needTruncation(TruncateKind kind) { // Remember analysis, needed for fallible checks. setTruncateKind(kind); return type() == MIRType::Double || type() == MIRType::Int32; } void MDiv::truncate() { MOZ_ASSERT(needTruncation(truncateKind())); specialization_ = MIRType::Int32; setResultType(MIRType::Int32); // Divisions where the lhs and rhs are unsigned and the result is // truncated can be lowered more efficiently. if (unsignedOperands()) { replaceWithUnsignedOperands(); unsigned_ = true; } } bool MMod::needTruncation(TruncateKind kind) { // Remember analysis, needed for fallible checks. setTruncateKind(kind); return type() == MIRType::Double || type() == MIRType::Int32; } void MMod::truncate() { // As for division, handle unsigned modulus with a truncated result. MOZ_ASSERT(needTruncation(truncateKind())); specialization_ = MIRType::Int32; setResultType(MIRType::Int32); if (unsignedOperands()) { replaceWithUnsignedOperands(); unsigned_ = true; } } bool MToDouble::needTruncation(TruncateKind kind) { MOZ_ASSERT(type() == MIRType::Double); setTruncateKind(kind); return true; } void MToDouble::truncate() { MOZ_ASSERT(needTruncation(truncateKind())); // We use the return type to flag that this MToDouble should be replaced by // a MTruncateToInt32 when modifying the graph. setResultType(MIRType::Int32); if (truncateKind() >= IndirectTruncate) { if (range()) range()->wrapAroundToInt32(); } } bool MLoadTypedArrayElementStatic::needTruncation(TruncateKind kind) { // IndirectTruncate not possible, since it returns 'undefined' // upon out of bounds read. Doing arithmetic on 'undefined' gives wrong // results. So only set infallible if explicitly truncated. if (kind == Truncate) setInfallible(); return false; } bool MLimitedTruncate::needTruncation(TruncateKind kind) { setTruncateKind(kind); setResultType(MIRType::Int32); if (kind >= IndirectTruncate && range()) range()->wrapAroundToInt32(); return false; } bool MCompare::needTruncation(TruncateKind kind) { // If we're compiling wasm, don't try to optimize the comparison type, as // the code presumably is already using the type it wants. Also, wasm // doesn't support bailouts, so we woudn't be able to rely on // TruncateAfterBailouts to convert our inputs. if (block()->info().compilingWasm()) return false; if (!isDoubleComparison()) return false; // If both operands are naturally in the int32 range, we can convert from // a double comparison to being an int32 comparison. if (!Range(lhs()).isInt32() || !Range(rhs()).isInt32()) return false; return true; } void MCompare::truncate() { compareType_ = Compare_Int32; // Truncating the operands won't change their value because we don't force a // truncation, but it will change their type, which we need because we // now expect integer inputs. truncateOperands_ = true; } MDefinition::TruncateKind MDefinition::operandTruncateKind(size_t index) const { // Generic routine: We don't know anything. return NoTruncate; } MDefinition::TruncateKind MPhi::operandTruncateKind(size_t index) const { // The truncation applied to a phi is effectively applied to the phi's // operands. return truncateKind_; } MDefinition::TruncateKind MTruncateToInt32::operandTruncateKind(size_t index) const { // This operator is an explicit truncate to int32. return Truncate; } MDefinition::TruncateKind MBinaryBitwiseInstruction::operandTruncateKind(size_t index) const { // The bitwise operators truncate to int32. return Truncate; } MDefinition::TruncateKind MLimitedTruncate::operandTruncateKind(size_t index) const { return Min(truncateKind(), truncateLimit_); } MDefinition::TruncateKind MAdd::operandTruncateKind(size_t index) const { // This operator is doing some arithmetic. If its result is truncated, // it's an indirect truncate for its operands. return Min(truncateKind(), IndirectTruncate); } MDefinition::TruncateKind MSub::operandTruncateKind(size_t index) const { // See the comment in MAdd::operandTruncateKind. return Min(truncateKind(), IndirectTruncate); } MDefinition::TruncateKind MMul::operandTruncateKind(size_t index) const { // See the comment in MAdd::operandTruncateKind. return Min(truncateKind(), IndirectTruncate); } MDefinition::TruncateKind MToDouble::operandTruncateKind(size_t index) const { // MToDouble propagates its truncate kind to its operand. return truncateKind(); } MDefinition::TruncateKind MStoreUnboxedScalar::operandTruncateKind(size_t index) const { // Some receiver objects, such as typed arrays, will truncate out of range integer inputs. return (truncateInput() && index == 2 && isIntegerWrite()) ? Truncate : NoTruncate; } MDefinition::TruncateKind MStoreTypedArrayElementHole::operandTruncateKind(size_t index) const { // An integer store truncates the stored value. return index == 3 && isIntegerWrite() ? Truncate : NoTruncate; } MDefinition::TruncateKind MStoreTypedArrayElementStatic::operandTruncateKind(size_t index) const { // An integer store truncates the stored value. return index == 1 && isIntegerWrite() ? Truncate : NoTruncate; } MDefinition::TruncateKind MDiv::operandTruncateKind(size_t index) const { return Min(truncateKind(), TruncateAfterBailouts); } MDefinition::TruncateKind MMod::operandTruncateKind(size_t index) const { return Min(truncateKind(), TruncateAfterBailouts); } MDefinition::TruncateKind MCompare::operandTruncateKind(size_t index) const { // If we're doing an int32 comparison on operands which were previously // floating-point, convert them! MOZ_ASSERT_IF(truncateOperands_, isInt32Comparison()); return truncateOperands_ ? TruncateAfterBailouts : NoTruncate; } static bool TruncateTest(TempAllocator& alloc, MTest* test) { // If all possible inputs to the test are either int32 or boolean, // convert those inputs to int32 so that an int32 test can be performed. if (test->input()->type() != MIRType::Value) return true; if (!test->input()->isPhi() || !test->input()->hasOneDefUse() || test->input()->isImplicitlyUsed()) return true; MPhi* phi = test->input()->toPhi(); for (size_t i = 0; i < phi->numOperands(); i++) { MDefinition* def = phi->getOperand(i); if (!def->isBox()) return true; MDefinition* inner = def->getOperand(0); if (inner->type() != MIRType::Boolean && inner->type() != MIRType::Int32) return true; } for (size_t i = 0; i < phi->numOperands(); i++) { MDefinition* inner = phi->getOperand(i)->getOperand(0); if (inner->type() != MIRType::Int32) { if (!alloc.ensureBallast()) return false; MBasicBlock* block = inner->block(); inner = MToInt32::New(alloc, inner); block->insertBefore(block->lastIns(), inner->toInstruction()); } MOZ_ASSERT(inner->type() == MIRType::Int32); phi->replaceOperand(i, inner); } phi->setResultType(MIRType::Int32); return true; } // Truncating instruction result is an optimization which implies // knowing all uses of an instruction. This implies that if one of // the uses got removed, then Range Analysis is not be allowed to do // any modification which can change the result, especially if the // result can be observed. // // This corner can easily be understood with UCE examples, but it // might also happen with type inference assumptions. Note: Type // inference is implicitly branches where other types might be // flowing into. static bool CloneForDeadBranches(TempAllocator& alloc, MInstruction* candidate) { // Compare returns a boolean so it doesn't have to be recovered on bailout // because the output would remain correct. if (candidate->isCompare()) return true; MOZ_ASSERT(candidate->canClone()); if (!alloc.ensureBallast()) return false; MDefinitionVector operands(alloc); size_t end = candidate->numOperands(); if (!operands.reserve(end)) return false; for (size_t i = 0; i < end; ++i) operands.infallibleAppend(candidate->getOperand(i)); MInstruction* clone = candidate->clone(alloc, operands); clone->setRange(nullptr); // Set UseRemoved flag on the cloned instruction in order to chain recover // instruction for the bailout path. clone->setUseRemovedUnchecked(); candidate->block()->insertBefore(candidate, clone); if (!candidate->maybeConstantValue()) { MOZ_ASSERT(clone->canRecoverOnBailout()); clone->setRecoveredOnBailout(); } // Replace the candidate by its recovered on bailout clone within recovered // instructions and resume points operands. for (MUseIterator i(candidate->usesBegin()); i != candidate->usesEnd(); ) { MUse* use = *i++; MNode* ins = use->consumer(); if (ins->isDefinition() && !ins->toDefinition()->isRecoveredOnBailout()) continue; use->replaceProducer(clone); } return true; } // Examine all the users of |candidate| and determine the most aggressive // truncate kind that satisfies all of them. static MDefinition::TruncateKind ComputeRequestedTruncateKind(MDefinition* candidate, bool* shouldClone) { bool isCapturedResult = false; // Check if used by a recovered instruction or a resume point. bool isObservableResult = false; // Check if it can be read from another frame. bool isRecoverableResult = true; // Check if it can safely be reconstructed. bool hasUseRemoved = candidate->isUseRemoved(); MDefinition::TruncateKind kind = MDefinition::Truncate; for (MUseIterator use(candidate->usesBegin()); use != candidate->usesEnd(); use++) { if (use->consumer()->isResumePoint()) { // Truncation is a destructive optimization, as such, we need to pay // attention to removed branches and prevent optimization // destructive optimizations if we have no alternative. (see // UseRemoved flag) isCapturedResult = true; isObservableResult = isObservableResult || use->consumer()->toResumePoint()->isObservableOperand(*use); isRecoverableResult = isRecoverableResult && use->consumer()->toResumePoint()->isRecoverableOperand(*use); continue; } MDefinition* consumer = use->consumer()->toDefinition(); if (consumer->isRecoveredOnBailout()) { isCapturedResult = true; hasUseRemoved = hasUseRemoved || consumer->isUseRemoved(); continue; } MDefinition::TruncateKind consumerKind = consumer->operandTruncateKind(consumer->indexOf(*use)); kind = Min(kind, consumerKind); if (kind == MDefinition::NoTruncate) break; } // We cannot do full trunction on guarded instructions. if (candidate->isGuard() || candidate->isGuardRangeBailouts()) kind = Min(kind, MDefinition::TruncateAfterBailouts); // If the value naturally produces an int32 value (before bailout checks) // that needs no conversion, we don't have to worry about resume points // seeing truncated values. bool needsConversion = !candidate->range() || !candidate->range()->isInt32(); // If the instruction is explicitly truncated (not indirectly) by all its // uses and if it has no removed uses, then we can safely encode its // truncated result as part of the resume point operands. This is safe, // because even if we resume with a truncated double, the next baseline // instruction operating on this instruction is going to be a no-op. // // Note, that if the result can be observed from another frame, then this // optimization is not safe. bool safeToConvert = kind == MDefinition::Truncate && !hasUseRemoved && !isObservableResult; // If the candidate instruction appears as operand of a resume point or a // recover instruction, and we have to truncate its result, then we might // have to either recover the result during the bailout, or avoid the // truncation. if (isCapturedResult && needsConversion && !safeToConvert) { // If the result can be recovered from all the resume points (not needed // for iterating over the inlined frames), and this instruction can be // recovered on bailout, then we can clone it and use the cloned // instruction to encode the recover instruction. Otherwise, we should // keep the original result and bailout if the value is not in the int32 // range. if (!JitOptions.disableRecoverIns && isRecoverableResult && candidate->canRecoverOnBailout()) *shouldClone = true; else kind = Min(kind, MDefinition::TruncateAfterBailouts); } return kind; } static MDefinition::TruncateKind ComputeTruncateKind(MDefinition* candidate, bool* shouldClone) { // Compare operations might coerce its inputs to int32 if the ranges are // correct. So we do not need to check if all uses are coerced. if (candidate->isCompare()) return MDefinition::TruncateAfterBailouts; // Set truncated flag if range analysis ensure that it has no // rounding errors and no fractional part. Note that we can't use // the MDefinition Range constructor, because we need to know if // the value will have rounding errors before any bailout checks. const Range* r = candidate->range(); bool canHaveRoundingErrors = !r || r->canHaveRoundingErrors(); // Special case integer division and modulo: a/b can be infinite, and a%b // can be NaN but cannot actually have rounding errors induced by truncation. if ((candidate->isDiv() || candidate->isMod()) && static_cast<const MBinaryArithInstruction *>(candidate)->specialization() == MIRType::Int32) { canHaveRoundingErrors = false; } if (canHaveRoundingErrors) return MDefinition::NoTruncate; // Ensure all observable uses are truncated. return ComputeRequestedTruncateKind(candidate, shouldClone); } static void RemoveTruncatesOnOutput(MDefinition* truncated) { // Compare returns a boolean so it doen't have any output truncates. if (truncated->isCompare()) return; MOZ_ASSERT(truncated->type() == MIRType::Int32); MOZ_ASSERT(Range(truncated).isInt32()); for (MUseDefIterator use(truncated); use; use++) { MDefinition* def = use.def(); if (!def->isTruncateToInt32() || !def->isToInt32()) continue; def->replaceAllUsesWith(truncated); } } static void AdjustTruncatedInputs(TempAllocator& alloc, MDefinition* truncated) { MBasicBlock* block = truncated->block(); for (size_t i = 0, e = truncated->numOperands(); i < e; i++) { MDefinition::TruncateKind kind = truncated->operandTruncateKind(i); if (kind == MDefinition::NoTruncate) continue; MDefinition* input = truncated->getOperand(i); if (input->type() == MIRType::Int32) continue; if (input->isToDouble() && input->getOperand(0)->type() == MIRType::Int32) { truncated->replaceOperand(i, input->getOperand(0)); } else { MInstruction* op; if (kind == MDefinition::TruncateAfterBailouts) op = MToInt32::New(alloc, truncated->getOperand(i)); else op = MTruncateToInt32::New(alloc, truncated->getOperand(i)); if (truncated->isPhi()) { MBasicBlock* pred = block->getPredecessor(i); pred->insertBefore(pred->lastIns(), op); } else { block->insertBefore(truncated->toInstruction(), op); } truncated->replaceOperand(i, op); } } if (truncated->isToDouble()) { truncated->replaceAllUsesWith(truncated->toToDouble()->getOperand(0)); block->discard(truncated->toToDouble()); } } // Iterate backward on all instruction and attempt to truncate operations for // each instruction which respect the following list of predicates: Has been // analyzed by range analysis, the range has no rounding errors, all uses cases // are truncating the result. // // If the truncation of the operation is successful, then the instruction is // queue for later updating the graph to restore the type correctness by // converting the operands that need to be truncated. // // We iterate backward because it is likely that a truncated operation truncates // some of its operands. bool RangeAnalysis::truncate() { JitSpew(JitSpew_Range, "Do range-base truncation (backward loop)"); // Automatic truncation is disabled for wasm because the truncation logic // is based on IonMonkey which assumes that we can bailout if the truncation // logic fails. As wasm code has no bailout mechanism, it is safer to avoid // any automatic truncations. MOZ_ASSERT(!mir->compilingWasm()); Vector<MDefinition*, 16, SystemAllocPolicy> worklist; for (PostorderIterator block(graph_.poBegin()); block != graph_.poEnd(); block++) { for (MInstructionReverseIterator iter(block->rbegin()); iter != block->rend(); iter++) { if (iter->isRecoveredOnBailout()) continue; if (iter->type() == MIRType::None) { if (iter->isTest()) { if (!TruncateTest(alloc(), iter->toTest())) return false; } continue; } // Remember all bitop instructions for folding after range analysis. switch (iter->op()) { case MDefinition::Op_BitAnd: case MDefinition::Op_BitOr: case MDefinition::Op_BitXor: case MDefinition::Op_Lsh: case MDefinition::Op_Rsh: case MDefinition::Op_Ursh: if (!bitops.append(static_cast<MBinaryBitwiseInstruction*>(*iter))) return false; break; default:; } bool shouldClone = false; MDefinition::TruncateKind kind = ComputeTruncateKind(*iter, &shouldClone); if (kind == MDefinition::NoTruncate) continue; // Range Analysis is sometimes eager to do optimizations, even if we // are not be able to truncate an instruction. In such case, we // speculatively compile the instruction to an int32 instruction // while adding a guard. This is what is implied by // TruncateAfterBailout. // // If we already experienced an overflow bailout while executing // code within the current JSScript, we no longer attempt to make // this kind of eager optimizations. if (kind <= MDefinition::TruncateAfterBailouts && block->info().hadOverflowBailout()) continue; // Truncate this instruction if possible. if (!iter->needTruncation(kind)) continue; SpewTruncate(*iter, kind, shouldClone); // If needed, clone the current instruction for keeping it for the // bailout path. This give us the ability to truncate instructions // even after the removal of branches. if (shouldClone && !CloneForDeadBranches(alloc(), *iter)) return false; iter->truncate(); // Delay updates of inputs/outputs to avoid creating node which // would be removed by the truncation of the next operations. iter->setInWorklist(); if (!worklist.append(*iter)) return false; } for (MPhiIterator iter(block->phisBegin()), end(block->phisEnd()); iter != end; ++iter) { bool shouldClone = false; MDefinition::TruncateKind kind = ComputeTruncateKind(*iter, &shouldClone); if (kind == MDefinition::NoTruncate) continue; // Truncate this phi if possible. if (shouldClone || !iter->needTruncation(kind)) continue; SpewTruncate(*iter, kind, shouldClone); iter->truncate(); // Delay updates of inputs/outputs to avoid creating node which // would be removed by the truncation of the next operations. iter->setInWorklist(); if (!worklist.append(*iter)) return false; } } // Update inputs/outputs of truncated instructions. JitSpew(JitSpew_Range, "Do graph type fixup (dequeue)"); while (!worklist.empty()) { if (!alloc().ensureBallast()) return false; MDefinition* def = worklist.popCopy(); def->setNotInWorklist(); RemoveTruncatesOnOutput(def); AdjustTruncatedInputs(alloc(), def); } return true; } bool RangeAnalysis::removeUnnecessaryBitops() { // Note: This operation change the semantic of the program in a way which // uniquely works with Int32, Recover Instructions added by the Sink phase // expects the MIR Graph to still have a valid flow as-if they were double // operations instead of Int32 operations. Thus, this phase should be // executed after the Sink phase, and before DCE. // Fold any unnecessary bitops in the graph, such as (x | 0) on an integer // input. This is done after range analysis rather than during GVN as the // presence of the bitop can change which instructions are truncated. for (size_t i = 0; i < bitops.length(); i++) { MBinaryBitwiseInstruction* ins = bitops[i]; if (ins->isRecoveredOnBailout()) continue; MDefinition* folded = ins->foldUnnecessaryBitop(); if (folded != ins) { ins->replaceAllLiveUsesWith(folded); ins->setRecoveredOnBailout(); } } bitops.clear(); return true; } /////////////////////////////////////////////////////////////////////////////// // Collect Range information of operands /////////////////////////////////////////////////////////////////////////////// void MInArray::collectRangeInfoPreTrunc() { Range indexRange(index()); if (indexRange.isFiniteNonNegative()) needsNegativeIntCheck_ = false; } void MLoadElementHole::collectRangeInfoPreTrunc() { Range indexRange(index()); if (indexRange.isFiniteNonNegative()) { needsNegativeIntCheck_ = false; setNotGuard(); } } void MLoadTypedArrayElementStatic::collectRangeInfoPreTrunc() { Range range(ptr()); if (range.hasInt32LowerBound() && range.hasInt32UpperBound()) { int64_t offset = this->offset(); int64_t lower = range.lower() + offset; int64_t upper = range.upper() + offset; int64_t length = this->length(); if (lower >= 0 && upper < length) setNeedsBoundsCheck(false); } } void MStoreTypedArrayElementStatic::collectRangeInfoPreTrunc() { Range range(ptr()); if (range.hasInt32LowerBound() && range.hasInt32UpperBound()) { int64_t offset = this->offset(); int64_t lower = range.lower() + offset; int64_t upper = range.upper() + offset; int64_t length = this->length(); if (lower >= 0 && upper < length) setNeedsBoundsCheck(false); } } void MClz::collectRangeInfoPreTrunc() { Range inputRange(input()); if (!inputRange.canBeZero()) operandIsNeverZero_ = true; } void MCtz::collectRangeInfoPreTrunc() { Range inputRange(input()); if (!inputRange.canBeZero()) operandIsNeverZero_ = true; } void MDiv::collectRangeInfoPreTrunc() { Range lhsRange(lhs()); Range rhsRange(rhs()); // Test if Dividend is non-negative. if (lhsRange.isFiniteNonNegative()) canBeNegativeDividend_ = false; // Try removing divide by zero check. if (!rhsRange.canBeZero()) canBeDivideByZero_ = false; // If lhsRange does not contain INT32_MIN in its range, // negative overflow check can be skipped. if (!lhsRange.contains(INT32_MIN)) canBeNegativeOverflow_ = false; // If rhsRange does not contain -1 likewise. if (!rhsRange.contains(-1)) canBeNegativeOverflow_ = false; // If lhsRange does not contain a zero, // negative zero check can be skipped. if (!lhsRange.canBeZero()) canBeNegativeZero_ = false; // If rhsRange >= 0 negative zero check can be skipped. if (rhsRange.isFiniteNonNegative()) canBeNegativeZero_ = false; } void MMul::collectRangeInfoPreTrunc() { Range lhsRange(lhs()); Range rhsRange(rhs()); // If lhsRange contains only positive then we can skip negative zero check. if (lhsRange.isFiniteNonNegative() && !lhsRange.canBeZero()) setCanBeNegativeZero(false); // Likewise rhsRange. if (rhsRange.isFiniteNonNegative() && !rhsRange.canBeZero()) setCanBeNegativeZero(false); // If rhsRange and lhsRange contain Non-negative integers only, // We skip negative zero check. if (rhsRange.isFiniteNonNegative() && lhsRange.isFiniteNonNegative()) setCanBeNegativeZero(false); //If rhsRange and lhsRange < 0. Then we skip negative zero check. if (rhsRange.isFiniteNegative() && lhsRange.isFiniteNegative()) setCanBeNegativeZero(false); } void MMod::collectRangeInfoPreTrunc() { Range lhsRange(lhs()); Range rhsRange(rhs()); if (lhsRange.isFiniteNonNegative()) canBeNegativeDividend_ = false; if (!rhsRange.canBeZero()) canBeDivideByZero_ = false; } void MToInt32::collectRangeInfoPreTrunc() { Range inputRange(input()); if (!inputRange.canBeNegativeZero()) canBeNegativeZero_ = false; } void MBoundsCheck::collectRangeInfoPreTrunc() { Range indexRange(index()); Range lengthRange(length()); if (!indexRange.hasInt32LowerBound() || !indexRange.hasInt32UpperBound()) return; if (!lengthRange.hasInt32LowerBound() || lengthRange.canBeNaN()) return; int64_t indexLower = indexRange.lower(); int64_t indexUpper = indexRange.upper(); int64_t lengthLower = lengthRange.lower(); int64_t min = minimum(); int64_t max = maximum(); if (indexLower + min >= 0 && indexUpper + max < lengthLower) fallible_ = false; } void MBoundsCheckLower::collectRangeInfoPreTrunc() { Range indexRange(index()); if (indexRange.hasInt32LowerBound() && indexRange.lower() >= minimum_) fallible_ = false; } void MCompare::collectRangeInfoPreTrunc() { if (!Range(lhs()).canBeNaN() && !Range(rhs()).canBeNaN()) operandsAreNeverNaN_ = true; } void MNot::collectRangeInfoPreTrunc() { if (!Range(input()).canBeNaN()) operandIsNeverNaN_ = true; } void MPowHalf::collectRangeInfoPreTrunc() { Range inputRange(input()); if (!inputRange.canBeInfiniteOrNaN() || inputRange.hasInt32LowerBound()) operandIsNeverNegativeInfinity_ = true; if (!inputRange.canBeNegativeZero()) operandIsNeverNegativeZero_ = true; if (!inputRange.canBeNaN()) operandIsNeverNaN_ = true; } void MUrsh::collectRangeInfoPreTrunc() { if (specialization_ == MIRType::Int64) return; Range lhsRange(lhs()), rhsRange(rhs()); // As in MUrsh::computeRange(), convert the inputs. lhsRange.wrapAroundToInt32(); rhsRange.wrapAroundToShiftCount(); // If the most significant bit of our result is always going to be zero, // we can optimize by disabling bailout checks for enforcing an int32 range. if (lhsRange.lower() >= 0 || rhsRange.lower() >= 1) bailoutsDisabled_ = true; } static bool DoesMaskMatchRange(int32_t mask, Range& range) { // Check if range is positive, because the bitand operator in `(-3) & 0xff` can't be // eliminated. if (range.lower() >= 0) { MOZ_ASSERT(range.isInt32()); // Check that the mask value has all bits set given the range upper bound. Note that the // upper bound does not have to be exactly the mask value. For example, consider `x & // 0xfff` where `x` is a uint8. That expression can still be optimized to `x`. int bits = 1 + FloorLog2(range.upper()); uint32_t maskNeeded = (bits == 32) ? 0xffffffff : (uint32_t(1) << bits) - 1; if ((mask & maskNeeded) == maskNeeded) return true; } return false; } void MBinaryBitwiseInstruction::collectRangeInfoPreTrunc() { Range lhsRange(lhs()); Range rhsRange(rhs()); if (lhs()->isConstant() && lhs()->type() == MIRType::Int32 && DoesMaskMatchRange(lhs()->toConstant()->toInt32(), rhsRange)) { maskMatchesRightRange = true; } if (rhs()->isConstant() && rhs()->type() == MIRType::Int32 && DoesMaskMatchRange(rhs()->toConstant()->toInt32(), lhsRange)) { maskMatchesLeftRange = true; } } void MNaNToZero::collectRangeInfoPreTrunc() { Range inputRange(input()); if (!inputRange.canBeNaN()) operandIsNeverNaN_ = true; if (!inputRange.canBeNegativeZero()) operandIsNeverNegativeZero_ = true; } bool RangeAnalysis::prepareForUCE(bool* shouldRemoveDeadCode) { *shouldRemoveDeadCode = false; for (ReversePostorderIterator iter(graph_.rpoBegin()); iter != graph_.rpoEnd(); iter++) { MBasicBlock* block = *iter; if (!block->unreachable()) continue; // Filter out unreachable fake entries. if (block->numPredecessors() == 0) { // Ignore fixup blocks added by the Value Numbering phase, in order // to keep the dominator tree as-is when we have OSR Block which are // no longer reachable from the main entry point of the graph. MOZ_ASSERT(graph_.osrBlock()); continue; } MControlInstruction* cond = block->getPredecessor(0)->lastIns(); if (!cond->isTest()) continue; // Replace the condition of the test control instruction by a constant // chosen based which of the successors has the unreachable flag which is // added by MBeta::computeRange on its own block. MTest* test = cond->toTest(); MDefinition* condition = test->input(); // If the false-branch is unreachable, then the test condition must be true. // If the true-branch is unreachable, then the test condition must be false. MOZ_ASSERT(block == test->ifTrue() || block == test->ifFalse()); bool value = block == test->ifFalse(); MConstant* constant = MConstant::New(alloc().fallible(), BooleanValue(value)); if (!constant) return false; condition->setGuardRangeBailoutsUnchecked(); test->block()->insertBefore(test, constant); test->replaceOperand(0, constant); JitSpew(JitSpew_Range, "Update condition of %d to reflect unreachable branches.", test->id()); *shouldRemoveDeadCode = true; } return tryRemovingGuards(); } bool RangeAnalysis::tryRemovingGuards() { MDefinitionVector guards(alloc()); for (ReversePostorderIterator block = graph_.rpoBegin(); block != graph_.rpoEnd(); block++) { for (MDefinitionIterator iter(*block); iter; iter++) { if (!iter->isGuardRangeBailouts()) continue; iter->setInWorklist(); if (!guards.append(*iter)) return false; } } // Flag all fallible instructions which were indirectly used in the // computation of the condition, such that we do not ignore // bailout-paths which are used to shrink the input range of the // operands of the condition. for (size_t i = 0; i < guards.length(); i++) { MDefinition* guard = guards[i]; // If this ins is a guard even without guardRangeBailouts, // there is no reason in trying to hoist the guardRangeBailouts check. guard->setNotGuardRangeBailouts(); if (!DeadIfUnused(guard)) { guard->setGuardRangeBailouts(); continue; } guard->setGuardRangeBailouts(); if (!guard->isPhi()) { if (!guard->range()) continue; // Filter the range of the instruction based on its MIRType. Range typeFilteredRange(guard); // If the output range is updated by adding the inner range, // then the MIRType act as an effectful filter. As we do not know if // this filtered Range might change or not the result of the // previous comparison, we have to keep this instruction as a guard // because it has to bailout in order to restrict the Range to its // MIRType. if (typeFilteredRange.update(guard->range())) continue; } guard->setNotGuardRangeBailouts(); // Propagate the guard to its operands. for (size_t op = 0, e = guard->numOperands(); op < e; op++) { MDefinition* operand = guard->getOperand(op); // Already marked. if (operand->isInWorklist()) continue; MOZ_ASSERT(!operand->isGuardRangeBailouts()); operand->setInWorklist(); operand->setGuardRangeBailouts(); if (!guards.append(operand)) return false; } } for (size_t i = 0; i < guards.length(); i++) { MDefinition* guard = guards[i]; guard->setNotInWorklist(); } return true; }