Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 255 insertions, 0 deletions

diff --git a/js/src/jit/Sink.cpp b/js/src/jit/Sink.cpp
new file mode 100644
index 0000000000..36977fb93d
--- /dev/null
+++ b/js/src/jit/Sink.cpp
@@ -0,0 +1,255 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * 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 "jit/IonOptimizationLevels.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) {
+  JitSpew(JitSpew_Sink, "Begin");
+  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()) {
+          if (!consumerNode->toResumePoint()->isRecoverableOperand(*i)) {
+            hasLiveUses = true;
+          }
+          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);
+      if (!clone) {
+        return false;
+      }
+      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