[x64/ia32] Deal with the non-transitivity of InstructionSelector::CanCover() when folding loads int…

src/compiler/ia32/instruction-selector-ia32.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 // Adds IA32-specific methods for generating operands.
 class IA32OperandGenerator final : public OperandGenerator {
  public:
   explicit IA32OperandGenerator(InstructionSelector* selector)
       : OperandGenerator(selector) {}
 
   InstructionOperand UseByteRegister(Node* node) {
     // TODO(titzer): encode byte register use constraints.
     return UseFixed(node, edx);
   }
 
   InstructionOperand DefineAsByteRegister(Node* node) {
     // TODO(titzer): encode byte register def constraints.
     return DefineAsRegister(node);
   }
 
-  bool CanBeMemoryOperand(InstructionCode opcode, Node* node, Node* input) {
+  bool CanBeMemoryOperand(InstructionCode opcode, Node* node, Node* input,
+                          int effect_level) {
     if (input->opcode() != IrOpcode::kLoad ||
         !selector()->CanCover(node, input)) {
       return false;
     }
+    if (effect_level != selector()->GetEffectLevel(input)) {
+      return false;
+    }
     MachineRepresentation rep =
         LoadRepresentationOf(input->op()).representation();
     switch (opcode) {
       case kIA32Cmp:
       case kIA32Test:
         return rep == MachineRepresentation::kWord32 ||
                rep == MachineRepresentation::kTagged;
       case kIA32Cmp16:
       case kIA32Test16:
         return rep == MachineRepresentation::kWord16;
@@ skipping 1183 matching lines @@
 
 // Shared routine for multiple word compare operations.
 void VisitWordCompare(InstructionSelector* selector, Node* node,
                       InstructionCode opcode, FlagsContinuation* cont) {
   IA32OperandGenerator g(selector);
   Node* left = node->InputAt(0);
   Node* right = node->InputAt(1);
 
   InstructionCode narrowed_opcode = TryNarrowOpcodeSize(opcode, left, right);
 
+  int effect_level = selector->GetEffectLevel(node);
+  if (cont->IsBranch()) {
+    effect_level = selector->GetEffectLevel(
+        cont->true_block()->PredecessorAt(0)->control_input());
+  }
+
   // If one of the two inputs is an immediate, make sure it's on the right, or
   // if one of the two inputs is a memory operand, make sure it's on the left.
   if ((!g.CanBeImmediate(right) && g.CanBeImmediate(left)) ||
-      (g.CanBeMemoryOperand(narrowed_opcode, node, right) &&
-       !g.CanBeMemoryOperand(narrowed_opcode, node, left))) {
+      (g.CanBeMemoryOperand(narrowed_opcode, node, right, effect_level) &&
+       !g.CanBeMemoryOperand(narrowed_opcode, node, left, effect_level))) {
     if (!node->op()->HasProperty(Operator::kCommutative)) cont->Commute();
     std::swap(left, right);
   }
 
   // Match immediates on right side of comparison.
   if (g.CanBeImmediate(right)) {
-    if (g.CanBeMemoryOperand(opcode, node, left)) {
+    if (g.CanBeMemoryOperand(opcode, node, left, effect_level)) {
       // TODO(epertoso): we should use `narrowed_opcode' here once we match
       // immediates too.
       return VisitCompareWithMemoryOperand(selector, opcode, left,
                                            g.UseImmediate(right), cont);
     }
     return VisitCompare(selector, opcode, g.Use(left), g.UseImmediate(right),
                         cont);
   }
 
   // Match memory operands on left side of comparison.
-  if (g.CanBeMemoryOperand(narrowed_opcode, node, left)) {
+  if (g.CanBeMemoryOperand(narrowed_opcode, node, left, effect_level)) {
     bool needs_byte_register =
         narrowed_opcode == kIA32Test8 || narrowed_opcode == kIA32Cmp8;
     return VisitCompareWithMemoryOperand(
         selector, narrowed_opcode, left,
         needs_byte_register ? g.UseByteRegister(right) : g.UseRegister(right),
         cont);
   }
 
   if (g.CanBeBetterLeftOperand(right)) {
     if (!node->op()->HasProperty(Operator::kCommutative)) cont->Commute();
@@ skipping 378 matching lines @@
 // static
 MachineOperatorBuilder::AlignmentRequirements
 InstructionSelector::AlignmentRequirements() {
   return MachineOperatorBuilder::AlignmentRequirements::
       FullUnalignedAccessSupport();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8