Add m-esr52 at 52.6.0

1 files changed, 408 insertions, 0 deletions

diff --git a/js/src/jit/LoopUnroller.cpp b/js/src/jit/LoopUnroller.cpp
new file mode 100644
index 000000000..5481d6978
--- /dev/null
+++ b/js/src/jit/LoopUnroller.cpp
@@ -0,0 +1,408 @@
+/* -*- 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/LoopUnroller.h"
+
+#include "jit/MIRGraph.h"
+
+using namespace js;
+using namespace js::jit;
+
+using mozilla::ArrayLength;
+
+namespace {
+
+struct LoopUnroller
+{
+    typedef HashMap<MDefinition*, MDefinition*,
+                    PointerHasher<MDefinition*, 2>, SystemAllocPolicy> DefinitionMap;
+
+    explicit LoopUnroller(MIRGraph& graph)
+      : graph(graph), alloc(graph.alloc()),
+        header(nullptr), backedge(nullptr),
+        unrolledHeader(nullptr), unrolledBackedge(nullptr),
+        oldPreheader(nullptr), newPreheader(nullptr)
+    {}
+
+    MIRGraph& graph;
+    TempAllocator& alloc;
+
+    // Header and body of the original loop.
+    MBasicBlock* header;
+    MBasicBlock* backedge;
+
+    // Header and body of the unrolled loop.
+    MBasicBlock* unrolledHeader;
+    MBasicBlock* unrolledBackedge;
+
+    // Old and new preheaders. The old preheader starts out associated with the
+    // original loop, but becomes the preheader of the new loop. The new
+    // preheader will be given to the original loop.
+    MBasicBlock* oldPreheader;
+    MBasicBlock* newPreheader;
+
+    // Map terms in the original loop to terms in the current unrolled iteration.
+    DefinitionMap unrolledDefinitions;
+
+    MDefinition* getReplacementDefinition(MDefinition* def);
+    MResumePoint* makeReplacementResumePoint(MBasicBlock* block, MResumePoint* rp);
+    bool makeReplacementInstruction(MInstruction* ins);
+
+    void go(LoopIterationBound* bound);
+};
+
+} // namespace
+
+MDefinition*
+LoopUnroller::getReplacementDefinition(MDefinition* def)
+{
+    if (def->block()->id() < header->id()) {
+        // The definition is loop invariant.
+        return def;
+    }
+
+    DefinitionMap::Ptr p = unrolledDefinitions.lookup(def);
+    if (!p) {
+        // After phi analysis (TypeAnalyzer::replaceRedundantPhi) the resume
+        // point at the start of a block can contain definitions from within
+        // the block itself.
+        MOZ_ASSERT(def->isConstant());
+
+        MConstant* constant = MConstant::Copy(alloc, def->toConstant());
+        oldPreheader->insertBefore(*oldPreheader->begin(), constant);
+        return constant;
+    }
+
+    return p->value();
+}
+
+bool
+LoopUnroller::makeReplacementInstruction(MInstruction* ins)
+{
+    MDefinitionVector inputs(alloc);
+    for (size_t i = 0; i < ins->numOperands(); i++) {
+        MDefinition* old = ins->getOperand(i);
+        MDefinition* replacement = getReplacementDefinition(old);
+        if (!inputs.append(replacement))
+            return false;
+    }
+
+    MInstruction* clone = ins->clone(alloc, inputs);
+
+    unrolledBackedge->add(clone);
+
+    if (!unrolledDefinitions.putNew(ins, clone))
+        return false;
+
+    if (MResumePoint* old = ins->resumePoint()) {
+        MResumePoint* rp = makeReplacementResumePoint(unrolledBackedge, old);
+        clone->setResumePoint(rp);
+    }
+
+    return true;
+}
+
+MResumePoint*
+LoopUnroller::makeReplacementResumePoint(MBasicBlock* block, MResumePoint* rp)
+{
+    MDefinitionVector inputs(alloc);
+    for (size_t i = 0; i < rp->numOperands(); i++) {
+        MDefinition* old = rp->getOperand(i);
+        MDefinition* replacement = old->isUnused() ? old : getReplacementDefinition(old);
+        if (!inputs.append(replacement))
+            return nullptr;
+    }
+
+    MResumePoint* clone = MResumePoint::New(alloc, block, rp, inputs);
+    if (!clone)
+        return nullptr;
+
+    return clone;
+}
+
+void
+LoopUnroller::go(LoopIterationBound* bound)
+{
+    // For now we always unroll loops the same number of times.
+    static const size_t UnrollCount = 10;
+
+    JitSpew(JitSpew_Unrolling, "Attempting to unroll loop");
+
+    header = bound->header;
+
+    // UCE might have determined this isn't actually a loop.
+    if (!header->isLoopHeader())
+        return;
+
+    backedge = header->backedge();
+    oldPreheader = header->loopPredecessor();
+
+    MOZ_ASSERT(oldPreheader->numSuccessors() == 1);
+
+    // Only unroll loops with two blocks: an initial one ending with the
+    // bound's test, and the body ending with the backedge.
+    MTest* test = bound->test;
+    if (header->lastIns() != test)
+        return;
+    if (test->ifTrue() == backedge) {
+        if (test->ifFalse()->id() <= backedge->id())
+            return;
+    } else if (test->ifFalse() == backedge) {
+        if (test->ifTrue()->id() <= backedge->id())
+            return;
+    } else {
+        return;
+    }
+    if (backedge->numPredecessors() != 1 || backedge->numSuccessors() != 1)
+        return;
+    MOZ_ASSERT(backedge->phisEmpty());
+
+    MBasicBlock* bodyBlocks[] = { header, backedge };
+
+    // All instructions in the header and body must be clonable.
+    for (size_t i = 0; i < ArrayLength(bodyBlocks); i++) {
+        MBasicBlock* block = bodyBlocks[i];
+        for (MInstructionIterator iter(block->begin()); iter != block->end(); iter++) {
+            MInstruction* ins = *iter;
+            if (ins->canClone())
+                continue;
+            if (ins->isTest() || ins->isGoto() || ins->isInterruptCheck())
+                continue;
+#ifdef JS_JITSPEW
+            JitSpew(JitSpew_Unrolling, "Aborting: can't clone instruction %s", ins->opName());
+#endif
+            return;
+        }
+    }
+
+    // Compute the linear inequality we will use for exiting the unrolled loop:
+    //
+    // iterationBound - iterationCount - UnrollCount >= 0
+    //
+    LinearSum remainingIterationsInequality(bound->boundSum);
+    if (!remainingIterationsInequality.add(bound->currentSum, -1))
+        return;
+    if (!remainingIterationsInequality.add(-int32_t(UnrollCount)))
+        return;
+
+    // Terms in the inequality need to be either loop invariant or phis from
+    // the original header.
+    for (size_t i = 0; i < remainingIterationsInequality.numTerms(); i++) {
+        MDefinition* def = remainingIterationsInequality.term(i).term;
+        if (def->isDiscarded())
+            return;
+        if (def->block()->id() < header->id())
+            continue;
+        if (def->block() == header && def->isPhi())
+            continue;
+        return;
+    }
+
+    // OK, we've checked everything, now unroll the loop.
+
+    JitSpew(JitSpew_Unrolling, "Unrolling loop");
+
+    // The old preheader will go before the unrolled loop, and the old loop
+    // will need a new empty preheader.
+    const CompileInfo& info = oldPreheader->info();
+    if (header->trackedPc()) {
+        unrolledHeader =
+            MBasicBlock::New(graph, nullptr, info,
+                             oldPreheader, header->trackedSite(), MBasicBlock::LOOP_HEADER);
+        unrolledBackedge =
+            MBasicBlock::New(graph, nullptr, info,
+                             unrolledHeader, backedge->trackedSite(), MBasicBlock::NORMAL);
+        newPreheader =
+            MBasicBlock::New(graph, nullptr, info,
+                             unrolledHeader, oldPreheader->trackedSite(), MBasicBlock::NORMAL);
+    } else {
+        unrolledHeader = MBasicBlock::New(graph, info, oldPreheader, MBasicBlock::LOOP_HEADER);
+        unrolledBackedge = MBasicBlock::New(graph, info, unrolledHeader, MBasicBlock::NORMAL);
+        newPreheader = MBasicBlock::New(graph, info, unrolledHeader, MBasicBlock::NORMAL);
+    }
+
+    unrolledHeader->discardAllResumePoints();
+    unrolledBackedge->discardAllResumePoints();
+    newPreheader->discardAllResumePoints();
+
+    // Insert new blocks at their RPO position, and update block ids.
+    graph.insertBlockAfter(oldPreheader, unrolledHeader);
+    graph.insertBlockAfter(unrolledHeader, unrolledBackedge);
+    graph.insertBlockAfter(unrolledBackedge, newPreheader);
+    graph.renumberBlocksAfter(oldPreheader);
+
+    // We don't tolerate allocation failure after this point.
+    // TODO: This is a bit drastic, is it possible to improve this?
+    AutoEnterOOMUnsafeRegion oomUnsafe;
+
+    if (!unrolledDefinitions.init())
+        oomUnsafe.crash("LoopUnroller::go");
+
+    // Add phis to the unrolled loop header which correspond to the phis in the
+    // original loop header.
+    MOZ_ASSERT(header->getPredecessor(0) == oldPreheader);
+    for (MPhiIterator iter(header->phisBegin()); iter != header->phisEnd(); iter++) {
+        MPhi* old = *iter;
+        MOZ_ASSERT(old->numOperands() == 2);
+        MPhi* phi = MPhi::New(alloc);
+        phi->setResultType(old->type());
+        phi->setResultTypeSet(old->resultTypeSet());
+        phi->setRange(old->range());
+
+        unrolledHeader->addPhi(phi);
+
+        if (!phi->reserveLength(2))
+            oomUnsafe.crash("LoopUnroller::go");
+
+        // Set the first input for the phi for now. We'll set the second after
+        // finishing the unroll.
+        phi->addInput(old->getOperand(0));
+
+        // The old phi will now take the value produced by the unrolled loop.
+        old->replaceOperand(0, phi);
+
+        if (!unrolledDefinitions.putNew(old, phi))
+            oomUnsafe.crash("LoopUnroller::go");
+    }
+
+    // The loop condition can bail out on e.g. integer overflow, so make a
+    // resume point based on the initial resume point of the original header.
+    MResumePoint* headerResumePoint = header->entryResumePoint();
+    if (headerResumePoint) {
+        MResumePoint* rp = makeReplacementResumePoint(unrolledHeader, headerResumePoint);
+        if (!rp)
+            oomUnsafe.crash("LoopUnroller::makeReplacementResumePoint");
+        unrolledHeader->setEntryResumePoint(rp);
+
+        // Perform an interrupt check at the start of the unrolled loop.
+        unrolledHeader->add(MInterruptCheck::New(alloc));
+    }
+
+    // Generate code for the test in the unrolled loop.
+    for (size_t i = 0; i < remainingIterationsInequality.numTerms(); i++) {
+        MDefinition* def = remainingIterationsInequality.term(i).term;
+        MDefinition* replacement = getReplacementDefinition(def);
+        remainingIterationsInequality.replaceTerm(i, replacement);
+    }
+    MCompare* compare = ConvertLinearInequality(alloc, unrolledHeader, remainingIterationsInequality);
+    MTest* unrolledTest = MTest::New(alloc, compare, unrolledBackedge, newPreheader);
+    unrolledHeader->end(unrolledTest);
+
+    // Make an entry resume point for the unrolled body. The unrolled header
+    // does not have side effects on stack values, even if the original loop
+    // header does, so use the same resume point as for the unrolled header.
+    if (headerResumePoint) {
+        MResumePoint* rp = makeReplacementResumePoint(unrolledBackedge, headerResumePoint);
+        if (!rp)
+            oomUnsafe.crash("LoopUnroller::makeReplacementResumePoint");
+        unrolledBackedge->setEntryResumePoint(rp);
+    }
+
+    // Make an entry resume point for the new preheader. There are no
+    // instructions which use this but some other stuff wants one to be here.
+    if (headerResumePoint) {
+        MResumePoint* rp = makeReplacementResumePoint(newPreheader, headerResumePoint);
+        if (!rp)
+            oomUnsafe.crash("LoopUnroller::makeReplacementResumePoint");
+        newPreheader->setEntryResumePoint(rp);
+    }
+
+    // Generate the unrolled code.
+    MOZ_ASSERT(UnrollCount > 1);
+    size_t unrollIndex = 0;
+    while (true) {
+        // Clone the contents of the original loop into the unrolled loop body.
+        for (size_t i = 0; i < ArrayLength(bodyBlocks); i++) {
+            MBasicBlock* block = bodyBlocks[i];
+            for (MInstructionIterator iter(block->begin()); iter != block->end(); iter++) {
+                MInstruction* ins = *iter;
+                if (ins->canClone()) {
+                    if (!makeReplacementInstruction(*iter))
+                        oomUnsafe.crash("LoopUnroller::makeReplacementDefinition");
+                } else {
+                    // Control instructions are handled separately.
+                    MOZ_ASSERT(ins->isTest() || ins->isGoto() || ins->isInterruptCheck());
+                }
+            }
+        }
+
+        // Compute the value of each loop header phi after the execution of
+        // this unrolled iteration.
+        MDefinitionVector phiValues(alloc);
+        MOZ_ASSERT(header->getPredecessor(1) == backedge);
+        for (MPhiIterator iter(header->phisBegin()); iter != header->phisEnd(); iter++) {
+            MPhi* old = *iter;
+            MDefinition* oldInput = old->getOperand(1);
+            if (!phiValues.append(getReplacementDefinition(oldInput)))
+                oomUnsafe.crash("LoopUnroller::go");
+        }
+
+        unrolledDefinitions.clear();
+
+        if (unrollIndex == UnrollCount - 1) {
+            // We're at the end of the last unrolled iteration, set the
+            // backedge input for the unrolled loop phis.
+            size_t phiIndex = 0;
+            for (MPhiIterator iter(unrolledHeader->phisBegin()); iter != unrolledHeader->phisEnd(); iter++) {
+                MPhi* phi = *iter;
+                phi->addInput(phiValues[phiIndex++]);
+            }
+            MOZ_ASSERT(phiIndex == phiValues.length());
+            break;
+        }
+
+        // Update the map for the phis in the next iteration.
+        size_t phiIndex = 0;
+        for (MPhiIterator iter(header->phisBegin()); iter != header->phisEnd(); iter++) {
+            MPhi* old = *iter;
+            if (!unrolledDefinitions.putNew(old, phiValues[phiIndex++]))
+                oomUnsafe.crash("LoopUnroller::go");
+        }
+        MOZ_ASSERT(phiIndex == phiValues.length());
+
+        unrollIndex++;
+    }
+
+    MGoto* backedgeJump = MGoto::New(alloc, unrolledHeader);
+    unrolledBackedge->end(backedgeJump);
+
+    // Place the old preheader before the unrolled loop.
+    MOZ_ASSERT(oldPreheader->lastIns()->isGoto());
+    oldPreheader->discardLastIns();
+    oldPreheader->end(MGoto::New(alloc, unrolledHeader));
+
+    // Place the new preheader before the original loop.
+    newPreheader->end(MGoto::New(alloc, header));
+
+    // Cleanup the MIR graph.
+    if (!unrolledHeader->addPredecessorWithoutPhis(unrolledBackedge))
+        oomUnsafe.crash("LoopUnroller::go");
+    header->replacePredecessor(oldPreheader, newPreheader);
+    oldPreheader->setSuccessorWithPhis(unrolledHeader, 0);
+    newPreheader->setSuccessorWithPhis(header, 0);
+    unrolledBackedge->setSuccessorWithPhis(unrolledHeader, 1);
+}
+
+bool
+jit::UnrollLoops(MIRGraph& graph, const LoopIterationBoundVector& bounds)
+{
+    if (bounds.empty())
+        return true;
+
+    for (size_t i = 0; i < bounds.length(); i++) {
+        LoopUnroller unroller(graph);
+        unroller.go(bounds[i]);
+    }
+
+    // The MIR graph is valid, but now has several new blocks. Update or
+    // recompute previous analysis information for the remaining optimization
+    // passes.
+    ClearDominatorTree(graph);
+    if (!BuildDominatorTree(graph))
+        return false;
+
+    return true;
+}