From 5f8de423f190bbb79a62f804151bc24824fa32d8 Mon Sep 17 00:00:00 2001 From: "Matt A. Tobin" Date: Fri, 2 Feb 2018 04:16:08 -0500 Subject: Add m-esr52 at 52.6.0 --- js/src/jit/MoveResolver.cpp | 321 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 321 insertions(+) create mode 100644 js/src/jit/MoveResolver.cpp (limited to 'js/src/jit/MoveResolver.cpp') diff --git a/js/src/jit/MoveResolver.cpp b/js/src/jit/MoveResolver.cpp new file mode 100644 index 000000000..5fd6c7bd5 --- /dev/null +++ b/js/src/jit/MoveResolver.cpp @@ -0,0 +1,321 @@ +/* -*- 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/MoveResolver.h" + +#include "mozilla/Attributes.h" + +#include "jit/MacroAssembler.h" +#include "jit/RegisterSets.h" + +using namespace js; +using namespace js::jit; + +MoveOperand::MoveOperand(MacroAssembler& masm, const ABIArg& arg) +{ + switch (arg.kind()) { + case ABIArg::GPR: + kind_ = REG; + code_ = arg.gpr().code(); + break; +#ifdef JS_CODEGEN_REGISTER_PAIR + case ABIArg::GPR_PAIR: + kind_ = REG_PAIR; + code_ = arg.evenGpr().code(); + MOZ_ASSERT(code_ % 2 == 0); + MOZ_ASSERT(code_ + 1 == arg.oddGpr().code()); + break; +#endif + case ABIArg::FPU: + kind_ = FLOAT_REG; + code_ = arg.fpu().code(); + break; + case ABIArg::Stack: + kind_ = MEMORY; + code_ = masm.getStackPointer().code(); + disp_ = arg.offsetFromArgBase(); + break; + } +} + +MoveResolver::MoveResolver() + : numCycles_(0), curCycles_(0) +{ +} + +void +MoveResolver::resetState() +{ + numCycles_ = 0; + curCycles_ = 0; +} + +bool +MoveResolver::addMove(const MoveOperand& from, const MoveOperand& to, MoveOp::Type type) +{ + // Assert that we're not doing no-op moves. + MOZ_ASSERT(!(from == to)); + PendingMove* pm = movePool_.allocate(); + if (!pm) + return false; + new (pm) PendingMove(from, to, type); + pending_.pushBack(pm); + return true; +} + +// Given move (A -> B), this function attempts to find any move (B -> *) in the +// pending move list, and returns the first one. +MoveResolver::PendingMove* +MoveResolver::findBlockingMove(const PendingMove* last) +{ + for (PendingMoveIterator iter = pending_.begin(); iter != pending_.end(); iter++) { + PendingMove* other = *iter; + + if (other->from().aliases(last->to())) { + // We now have pairs in the form (A -> X) (X -> y). The second pair + // blocks the move in the first pair, so return it. + return other; + } + } + + // No blocking moves found. + return nullptr; +} + +// Given move (A -> B), this function attempts to find any move (B -> *) in the +// move list iterator, and returns the first one. +// N.B. It is unclear if a single move can complete more than one cycle, so to be +// conservative, this function operates on iterators, so the caller can process all +// instructions that start a cycle. +MoveResolver::PendingMove* +MoveResolver::findCycledMove(PendingMoveIterator* iter, PendingMoveIterator end, const PendingMove* last) +{ + for (; *iter != end; (*iter)++) { + PendingMove* other = **iter; + if (other->from().aliases(last->to())) { + // We now have pairs in the form (A -> X) (X -> y). The second pair + // blocks the move in the first pair, so return it. + (*iter)++; + return other; + } + } + // No blocking moves found. + return nullptr; +} + +bool +MoveResolver::resolve() +{ + resetState(); + orderedMoves_.clear(); + + InlineList stack; + + // This is a depth-first-search without recursion, which tries to find + // cycles in a list of moves. + // + // Algorithm. + // + // S = Traversal stack. + // P = Pending move list. + // O = Ordered list of moves. + // + // As long as there are pending moves in P: + // Let |root| be any pending move removed from P + // Add |root| to the traversal stack. + // As long as S is not empty: + // Let |L| be the most recent move added to S. + // + // Find any pending move M whose source is L's destination, thus + // preventing L's move until M has completed. + // + // If a move M was found, + // Remove M from the pending list. + // If M's destination is |root|, + // Annotate M and |root| as cycles. + // Add M to S. + // do not Add M to O, since M may have other conflictors in P that have not yet been processed. + // Otherwise, + // Add M to S. + // Otherwise, + // Remove L from S. + // Add L to O. + // + while (!pending_.empty()) { + PendingMove* pm = pending_.popBack(); + + // Add this pending move to the cycle detection stack. + stack.pushBack(pm); + + while (!stack.empty()) { + PendingMove* blocking = findBlockingMove(stack.peekBack()); + + if (blocking) { + PendingMoveIterator stackiter = stack.begin(); + PendingMove* cycled = findCycledMove(&stackiter, stack.end(), blocking); + if (cycled) { + // Find the cycle's start. + // We annotate cycles at each move in the cycle, and + // assert that we do not find two cycles in one move chain + // traversal (which would indicate two moves to the same + // destination). + // Since there can be more than one cycle, find them all. + do { + cycled->setCycleEnd(curCycles_); + cycled = findCycledMove(&stackiter, stack.end(), blocking); + } while (cycled); + + blocking->setCycleBegin(pm->type(), curCycles_); + curCycles_++; + pending_.remove(blocking); + stack.pushBack(blocking); + } else { + // This is a new link in the move chain, so keep + // searching for a cycle. + pending_.remove(blocking); + stack.pushBack(blocking); + } + } else { + // Otherwise, pop the last move on the search stack because it's + // complete and not participating in a cycle. The resulting + // move can safely be added to the ordered move list. + PendingMove* done = stack.popBack(); + if (!addOrderedMove(*done)) + return false; + movePool_.free(done); + } + } + // If the current queue is empty, it is certain that there are + // all previous cycles cannot conflict with future cycles, + // so re-set the counter of pending cycles, while keeping a high-water mark. + if (numCycles_ < curCycles_) + numCycles_ = curCycles_; + curCycles_ = 0; + } + + return true; +} + +bool +MoveResolver::addOrderedMove(const MoveOp& move) +{ + // Sometimes the register allocator generates move groups where multiple + // moves have the same source. Try to optimize these cases when the source + // is in memory and the target of one of the moves is in a register. + MOZ_ASSERT(!move.from().aliases(move.to())); + + if (!move.from().isMemory() || move.isCycleBegin() || move.isCycleEnd()) + return orderedMoves_.append(move); + + // Look for an earlier move with the same source, where no intervening move + // touches either the source or destination of the new move. + for (int i = orderedMoves_.length() - 1; i >= 0; i--) { + const MoveOp& existing = orderedMoves_[i]; + + if (existing.from() == move.from() && + !existing.to().aliases(move.to()) && + existing.type() == move.type() && + !existing.isCycleBegin() && + !existing.isCycleEnd()) + { + MoveOp* after = orderedMoves_.begin() + i + 1; + if (existing.to().isGeneralReg() || existing.to().isFloatReg()) { + MoveOp nmove(existing.to(), move.to(), move.type()); + return orderedMoves_.insert(after, nmove); + } else if (move.to().isGeneralReg() || move.to().isFloatReg()) { + MoveOp nmove(move.to(), existing.to(), move.type()); + orderedMoves_[i] = move; + return orderedMoves_.insert(after, nmove); + } + } + + if (existing.aliases(move)) + break; + } + + return orderedMoves_.append(move); +} + +void +MoveResolver::reorderMove(size_t from, size_t to) +{ + MOZ_ASSERT(from != to); + + MoveOp op = orderedMoves_[from]; + if (from < to) { + for (size_t i = from; i < to; i++) + orderedMoves_[i] = orderedMoves_[i + 1]; + } else { + for (size_t i = from; i > to; i--) + orderedMoves_[i] = orderedMoves_[i - 1]; + } + orderedMoves_[to] = op; +} + +void +MoveResolver::sortMemoryToMemoryMoves() +{ + // Try to reorder memory->memory moves so that they are executed right + // before a move that clobbers some register. This will allow the move + // emitter to use that clobbered register as a scratch register for the + // memory->memory move, if necessary. + for (size_t i = 0; i < orderedMoves_.length(); i++) { + const MoveOp& base = orderedMoves_[i]; + if (!base.from().isMemory() || !base.to().isMemory()) + continue; + if (base.type() != MoveOp::GENERAL && base.type() != MoveOp::INT32) + continue; + + // Look for an earlier move clobbering a register. + bool found = false; + for (int j = i - 1; j >= 0; j--) { + const MoveOp& previous = orderedMoves_[j]; + if (previous.aliases(base) || previous.isCycleBegin() || previous.isCycleEnd()) + break; + + if (previous.to().isGeneralReg()) { + reorderMove(i, j); + found = true; + break; + } + } + if (found) + continue; + + // Look for a later move clobbering a register. + if (i + 1 < orderedMoves_.length()) { + bool found = false, skippedRegisterUse = false; + for (size_t j = i + 1; j < orderedMoves_.length(); j++) { + const MoveOp& later = orderedMoves_[j]; + if (later.aliases(base) || later.isCycleBegin() || later.isCycleEnd()) + break; + + if (later.to().isGeneralReg()) { + if (skippedRegisterUse) { + reorderMove(i, j); + found = true; + } else { + // There is no move that uses a register between the + // original memory->memory move and this move that + // clobbers a register. The move should already be able + // to use a scratch register, so don't shift anything + // around. + } + break; + } + + if (later.from().isGeneralReg()) + skippedRegisterUse = true; + } + + if (found) { + // Redo the search for memory->memory moves at the current + // index, so we don't skip the move just shifted back. + i--; + } + } + } +} -- cgit v1.2.3