[turbofan] Byte and word memory operands in x64 cmp/test. Fixes arithmetic_op_8 in assembler-x64.cc

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 25 matching lines @@
     }
   }
 
   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;
+    switch (opcode) {
+      case kX64Cmp:
+      case kX64Test:
+        return rep == MachineRepresentation::kWord64 ||
+               rep == MachineRepresentation::kTagged;
+      case kX64Cmp32:
+      case kX64Test32:
+        return rep == MachineRepresentation::kWord32;
+      case kX64Cmp16:
+      case kX64Test16:
+        return rep == MachineRepresentation::kWord16;
+      case kX64Cmp8:
+      case kX64Test8:
+        return rep == MachineRepresentation::kWord8;
+      default:
+        break;
     }
     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) {
@@ skipping 1348 matching lines @@
 void VisitCompare(InstructionSelector* selector, InstructionCode opcode,
                   Node* left, Node* right, FlagsContinuation* cont,
                   bool commutative) {
   X64OperandGenerator g(selector);
   if (commutative && g.CanBeBetterLeftOperand(right)) {
     std::swap(left, right);
   }
   VisitCompare(selector, opcode, g.UseRegister(left), g.Use(right), cont);
 }
 
+// Tries to match the size of the given opcode to that of the operands, if
+// possible.
+InstructionCode TryNarrowOpcodeSize(InstructionCode opcode, Node* left,
+                                    Node* right) {
+  if (opcode != kX64Cmp32 && opcode != kX64Test32) {
+    return opcode;
+  }
+  if (left->opcode() != IrOpcode::kLoad || right->opcode() != IrOpcode::kLoad) {

[Jarin, 2016/03/14 14:54:08]

Could you add a comment explaining why you only consider loads?

[epertoso, 2016/03/15 14:38:46]

Done.

+    return opcode;
+  }
+  // If the load representations don't match, both operands will be
+  // zero/sign-extended to 32bit.
+  LoadRepresentation left_representation = LoadRepresentationOf(left->op());
+  if (left_representation != LoadRepresentationOf(right->op())) {
+    return opcode;
+  }
+  switch (left_representation.representation()) {
+    case MachineRepresentation::kBit:
+    case MachineRepresentation::kWord8:
+      return opcode == kX64Cmp32 ? kX64Cmp8 : kX64Test8;
+    case MachineRepresentation::kWord16:
+      return opcode == kX64Cmp32 ? kX64Cmp16 : kX64Test16;
+    default:
+      return opcode;
+  }
+}
+
 // 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);
 
+  opcode = TryNarrowOpcodeSize(opcode, left, right);
+
   // 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.
@@ skipping 491 matching lines @@
              MachineOperatorBuilder::kFloat64RoundTruncate |
              MachineOperatorBuilder::kFloat32RoundTiesEven |
              MachineOperatorBuilder::kFloat64RoundTiesEven;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8