[turbofan] Properly cover memory operands in comparisons.

src/compiler/x64/instruction-selector-x64.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 <algorithm>
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
@@ skipping 18 matching lines @@
       }
       case IrOpcode::kNumberConstant: {
         const double value = OpParameter<double>(node);
         return bit_cast<int64_t>(value) == 0;
       }
       default:
         return false;
     }
   }
 
+  bool CanBeMemoryOperand(InstructionCode opcode, Node* node, Node* input) {
+    if (input->opcode() != IrOpcode::kLoad ||
+        !selector()->CanCover(node, input)) {
+      return false;
+    }
+    MachineRepresentation rep =
+        LoadRepresentationOf(input->op()).representation();
+    if (rep == MachineRepresentation::kWord64 ||
+        rep == MachineRepresentation::kTagged) {
+      return opcode == kX64Cmp || opcode == kX64Test;
+    } else if (rep == MachineRepresentation::kWord32) {
+      return opcode == kX64Cmp32 || opcode == kX64Test32;
+    }
+    return false;
+  }
+
   AddressingMode GenerateMemoryOperandInputs(Node* index, int scale_exponent,
                                              Node* base, Node* displacement,
                                              InstructionOperand inputs[],
                                              size_t* input_count) {
     AddressingMode mode = kMode_MRI;
     if (base != nullptr) {
       inputs[(*input_count)++] = UseRegister(base);
       if (index != nullptr) {
         DCHECK(scale_exponent >= 0 && scale_exponent <= 3);
         inputs[(*input_count)++] = UseRegister(index);
@@ skipping 1307 matching lines @@
     inputs[input_count++] = g.Label(cont->true_block());
     inputs[input_count++] = g.Label(cont->false_block());
     selector->Emit(opcode, 0, nullptr, input_count, inputs);
   } else {
     DCHECK(cont->IsSet());
     InstructionOperand output = g.DefineAsRegister(cont->result());
     selector->Emit(opcode, 1, &output, input_count, inputs);
   }
 }
 
-// Determines if {input} of {node} can be replaced by a memory operand.
-bool CanUseMemoryOperand(InstructionSelector* selector, InstructionCode opcode,
-                         Node* node, Node* input) {
-  if (input->opcode() != IrOpcode::kLoad || !selector->CanCover(node, input)) {
-    return false;
-  }
-  MachineRepresentation rep =
-      LoadRepresentationOf(input->op()).representation();
-  if (rep == MachineRepresentation::kWord64 ||
-      rep == MachineRepresentation::kTagged) {
-    return opcode == kX64Cmp || opcode == kX64Test;
-  } else if (rep == MachineRepresentation::kWord32) {
-    return opcode == kX64Cmp32 || opcode == kX64Test32;
-  }
-  return false;
-}
-
 // Shared routine for multiple compare operations.
 void VisitCompare(InstructionSelector* selector, InstructionCode opcode,
                   InstructionOperand left, InstructionOperand right,
                   FlagsContinuation* cont) {
   X64OperandGenerator g(selector);
   opcode = cont->Encode(opcode);
   if (cont->IsBranch()) {
     selector->Emit(opcode, g.NoOutput(), left, right,
                    g.Label(cont->true_block()), g.Label(cont->false_block()));
   } else {
@@ skipping 14 matching lines @@
   VisitCompare(selector, opcode, g.UseRegister(left), g.Use(right), cont);
 }
 
 // Shared routine for multiple word compare operations.
 void VisitWordCompare(InstructionSelector* selector, Node* node,
                       InstructionCode opcode, FlagsContinuation* cont) {
   X64OperandGenerator g(selector);
   Node* left = node->InputAt(0);
   Node* right = node->InputAt(1);
 
-  // If one of the two inputs is an immediate, make sure it's on the right.
-  if (!g.CanBeImmediate(right) && g.CanBeImmediate(left)) {
+  // 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(opcode, node, right) &&
+       !g.CanBeMemoryOperand(opcode, node, left))) {
     if (!node->op()->HasProperty(Operator::kCommutative)) cont->Commute();
     std::swap(left, right);
   }
 
   // Match immediates on right side of comparison.
   if (g.CanBeImmediate(right)) {
-    if (CanUseMemoryOperand(selector, opcode, node, left)) {
+    if (g.CanBeMemoryOperand(opcode, node, left)) {
       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(opcode, node, left)) {
+    return VisitCompareWithMemoryOperand(selector, opcode, left,
+                                         g.UseRegister(right), cont);
+  }
+
   if (g.CanBeBetterLeftOperand(right)) {
     if (!node->op()->HasProperty(Operator::kCommutative)) cont->Commute();
     std::swap(left, right);
   }
 
-  if (CanUseMemoryOperand(selector, opcode, node, left)) {
-    return VisitCompareWithMemoryOperand(selector, opcode, left,
-                                         g.UseRegister(right), cont);
-  }
   return VisitCompare(selector, opcode, left, right, cont,
                       node->op()->HasProperty(Operator::kCommutative));
 }
 
 // Shared routine for 64-bit word comparison operations.
 void VisitWord64Compare(InstructionSelector* selector, Node* node,
                         FlagsContinuation* cont) {
   X64OperandGenerator g(selector);
   Int64BinopMatcher m(node);
   if (m.left().IsLoad() && m.right().IsLoadStackPointer()) {
@@ skipping 441 matching lines @@
              MachineOperatorBuilder::kFloat64RoundTruncate |
              MachineOperatorBuilder::kFloat32RoundTiesEven |
              MachineOperatorBuilder::kFloat64RoundTiesEven;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8