Add m-esr52 at 52.6.0

1 files changed, 232 insertions, 0 deletions

diff --git a/js/src/jit/Sink.cpp b/js/src/jit/Sink.cpp
new file mode 100644
index 000000000..b2c36fae5
--- /dev/null
+++ b/js/src/jit/Sink.cpp
@@ -0,0 +1,232 @@
+/* -*- 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/Sink.h"
+
+#include "mozilla/Vector.h"
+
+#include "jit/IonAnalysis.h"
+#include "jit/JitSpewer.h"
+#include "jit/MIR.h"
+#include "jit/MIRGenerator.h"
+#include "jit/MIRGraph.h"
+
+namespace js {
+namespace jit {
+
+// Given the last found common dominator and a new definition to dominate, the
+// CommonDominator function returns the basic block which dominate the last
+// common dominator and the definition. If no such block exists, then this
+// functions return null.
+static MBasicBlock*
+CommonDominator(MBasicBlock* commonDominator, MBasicBlock* defBlock)
+{
+    // This is the first instruction visited, record its basic block as being
+    // the only interesting one.
+    if (!commonDominator)
+        return defBlock;
+
+    // Iterate on immediate dominators of the known common dominator to find a
+    // block which dominates all previous uses as well as this instruction.
+    while (!commonDominator->dominates(defBlock)) {
+        MBasicBlock* nextBlock = commonDominator->immediateDominator();
+        // All uses are dominated, so, this cannot happen unless the graph
+        // coherency is not respected.
+        MOZ_ASSERT(commonDominator != nextBlock);
+        commonDominator = nextBlock;
+    }
+
+    return commonDominator;
+}
+
+bool
+Sink(MIRGenerator* mir, MIRGraph& graph)
+{
+    TempAllocator& alloc = graph.alloc();
+    bool sinkEnabled = mir->optimizationInfo().sinkEnabled();
+
+    for (PostorderIterator block = graph.poBegin(); block != graph.poEnd(); block++) {
+        if (mir->shouldCancel("Sink"))
+            return false;
+
+        for (MInstructionReverseIterator iter = block->rbegin(); iter != block->rend(); ) {
+            MInstruction* ins = *iter++;
+
+            // Only instructions which can be recovered on bailout can be moved
+            // into the bailout paths.
+            if (ins->isGuard() || ins->isGuardRangeBailouts() ||
+                ins->isRecoveredOnBailout() || !ins->canRecoverOnBailout())
+            {
+                continue;
+            }
+
+            // Compute a common dominator for all uses of the current
+            // instruction.
+            bool hasLiveUses = false;
+            bool hasUses = false;
+            MBasicBlock* usesDominator = nullptr;
+            for (MUseIterator i(ins->usesBegin()), e(ins->usesEnd()); i != e; i++) {
+                hasUses = true;
+                MNode* consumerNode = (*i)->consumer();
+                if (consumerNode->isResumePoint())
+                    continue;
+
+                MDefinition* consumer = consumerNode->toDefinition();
+                if (consumer->isRecoveredOnBailout())
+                    continue;
+
+                hasLiveUses = true;
+
+                // If the instruction is a Phi, then we should dominate the
+                // predecessor from which the value is coming from.
+                MBasicBlock* consumerBlock = consumer->block();
+                if (consumer->isPhi())
+                    consumerBlock = consumerBlock->getPredecessor(consumer->indexOf(*i));
+
+                usesDominator = CommonDominator(usesDominator, consumerBlock);
+                if (usesDominator == *block)
+                    break;
+            }
+
+            // Leave this instruction for DCE.
+            if (!hasUses)
+                continue;
+
+            // We have no uses, so sink this instruction in all the bailout
+            // paths.
+            if (!hasLiveUses) {
+                MOZ_ASSERT(!usesDominator);
+                ins->setRecoveredOnBailout();
+                JitSpewDef(JitSpew_Sink, "  No live uses, recover the instruction on bailout\n", ins);
+                continue;
+            }
+
+            // This guard is temporarly moved here as the above code deals with
+            // Dead Code elimination, which got moved into this Sink phase, as
+            // the Dead Code elimination used to move instructions with no-live
+            // uses to the bailout path.
+            if (!sinkEnabled)
+                continue;
+
+            // To move an effectful instruction, we would have to verify that the
+            // side-effect is not observed. In the mean time, we just inhibit
+            // this optimization on effectful instructions.
+            if (ins->isEffectful())
+                continue;
+
+            // If all the uses are under a loop, we might not want to work
+            // against LICM by moving everything back into the loop, but if the
+            // loop is it-self inside an if, then we still want to move the
+            // computation under this if statement.
+            while (block->loopDepth() < usesDominator->loopDepth()) {
+                MOZ_ASSERT(usesDominator != usesDominator->immediateDominator());
+                usesDominator = usesDominator->immediateDominator();
+            }
+
+            // Only move instructions if there is a branch between the dominator
+            // of the uses and the original instruction. This prevent moving the
+            // computation of the arguments into an inline function if there is
+            // no major win.
+            MBasicBlock* lastJoin = usesDominator;
+            while (*block != lastJoin && lastJoin->numPredecessors() == 1) {
+                MOZ_ASSERT(lastJoin != lastJoin->immediateDominator());
+                MBasicBlock* next = lastJoin->immediateDominator();
+                if (next->numSuccessors() > 1)
+                    break;
+                lastJoin = next;
+            }
+            if (*block == lastJoin)
+                continue;
+
+            // Skip to the next instruction if we cannot find a common dominator
+            // for all the uses of this instruction, or if the common dominator
+            // correspond to the block of the current instruction.
+            if (!usesDominator || usesDominator == *block)
+                continue;
+
+            // Only instruction which can be recovered on bailout and which are
+            // sinkable can be moved into blocks which are below while filling
+            // the resume points with a clone which is recovered on bailout.
+
+            // If the instruction has live uses and if it is clonable, then we
+            // can clone the instruction for all non-dominated uses and move the
+            // instruction into the block which is dominating all live uses.
+            if (!ins->canClone())
+                continue;
+
+            // If the block is a split-edge block, which is created for folding
+            // test conditions, then the block has no resume point and has
+            // multiple predecessors.  In such case, we cannot safely move
+            // bailing instruction to these blocks as we have no way to bailout.
+            if (!usesDominator->entryResumePoint() && usesDominator->numPredecessors() != 1)
+                continue;
+
+            JitSpewDef(JitSpew_Sink, "  Can Clone & Recover, sink instruction\n", ins);
+            JitSpew(JitSpew_Sink, "  into Block %u", usesDominator->id());
+
+            // Copy the arguments and clone the instruction.
+            MDefinitionVector operands(alloc);
+            for (size_t i = 0, end = ins->numOperands(); i < end; i++) {
+                if (!operands.append(ins->getOperand(i)))
+                    return false;
+            }
+
+            MInstruction* clone = ins->clone(alloc, operands);
+            ins->block()->insertBefore(ins, clone);
+            clone->setRecoveredOnBailout();
+
+            // We should not update the producer of the entry resume point, as
+            // it cannot refer to any instruction within the basic block excepts
+            // for Phi nodes.
+            MResumePoint* entry = usesDominator->entryResumePoint();
+
+            // Replace the instruction by its clone in all the resume points /
+            // recovered-on-bailout instructions which are not in blocks which
+            // are dominated by the usesDominator block.
+            for (MUseIterator i(ins->usesBegin()), e(ins->usesEnd()); i != e; ) {
+                MUse* use = *i++;
+                MNode* consumer = use->consumer();
+
+                // If the consumer is a Phi, then we look for the index of the
+                // use to find the corresponding predecessor block, which is
+                // then used as the consumer block.
+                MBasicBlock* consumerBlock = consumer->block();
+                if (consumer->isDefinition() && consumer->toDefinition()->isPhi()) {
+                    consumerBlock = consumerBlock->getPredecessor(
+                        consumer->toDefinition()->toPhi()->indexOf(use));
+                }
+
+                // Keep the current instruction for all dominated uses, except
+                // for the entry resume point of the block in which the
+                // instruction would be moved into.
+                if (usesDominator->dominates(consumerBlock) &&
+                    (!consumer->isResumePoint() || consumer->toResumePoint() != entry))
+                {
+                    continue;
+                }
+
+                use->replaceProducer(clone);
+            }
+
+            // As we move this instruction in a different block, we should
+            // verify that we do not carry over a resume point which would refer
+            // to an outdated state of the control flow.
+            if (ins->resumePoint())
+                ins->clearResumePoint();
+
+            // Now, that all uses which are not dominated by usesDominator are
+            // using the cloned instruction, we can safely move the instruction
+            // into the usesDominator block.
+            MInstruction* at = usesDominator->safeInsertTop(nullptr, MBasicBlock::IgnoreRecover);
+            block->moveBefore(at, ins);
+        }
+    }
+
+    return true;
+}
+
+} // namespace jit
+} // namespace js