[x86] Several small performance improvements.

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/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties-inl.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 241 matching lines @@
   IA32OperandGenerator g(selector);
   Int32BinopMatcher m(node);
   Node* left = m.left().node();
   Node* right = m.right().node();
   InstructionOperand* inputs[4];
   size_t input_count = 0;
   InstructionOperand* outputs[2];
   size_t output_count = 0;
 
   // TODO(turbofan): match complex addressing modes.
-  if (g.CanBeImmediate(right)) {
+  if (left == right) {
+    // If both inputs refer to the same operand, enforce allocating a register
+    // for both of them to ensure that we don't end up generating code like
+    // this:
+    //
+    //   mov eax, [ebp-0x10]
+    //   add eax, [ebp-0x10]
+    //   jo label
+    InstructionOperand* const input = g.UseRegister(left);
+    inputs[input_count++] = input;
+    inputs[input_count++] = input;
+  } else if (g.CanBeImmediate(right)) {
     inputs[input_count++] = g.UseRegister(left);
     inputs[input_count++] = g.UseImmediate(right);
   } else {
     if (node->op()->HasProperty(Operator::kCommutative) &&
         g.CanBeBetterLeftOperand(right)) {
       std::swap(left, right);
     }
     inputs[input_count++] = g.UseRegister(left);
     inputs[input_count++] = g.Use(right);
   }
@@ skipping 394 matching lines @@
     VisitCompare(selector, opcode, g.Use(left), g.UseImmediate(right), cont);
   } else if (g.CanBeImmediate(left)) {
     if (!commutative) cont->Commute();
     VisitCompare(selector, opcode, g.Use(right), g.UseImmediate(left), cont);
   } else {
     VisitCompare(selector, opcode, g.UseRegister(left), g.Use(right), cont);
   }
 }
 
 
-static void VisitWordTest(InstructionSelector* selector, Node* node,
-                          FlagsContinuation* cont) {
-  IA32OperandGenerator g(selector);
-  VisitCompare(selector, kIA32Test, g.Use(node), g.TempImmediate(-1), cont);
-}
-
-
 // Shared routine for multiple float compare operations.
 static void VisitFloat64Compare(InstructionSelector* selector, Node* node,
                                 FlagsContinuation* cont) {
   IA32OperandGenerator g(selector);
   Node* left = node->InputAt(0);
   Node* right = node->InputAt(1);
   VisitCompare(selector, kSSEFloat64Cmp, g.UseRegister(left), g.Use(right),
                cont);
 }
 
 
 void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
                                       BasicBlock* fbranch) {
-  OperandGenerator g(this);
+  IA32OperandGenerator g(this);
   Node* user = branch;
   Node* value = branch->InputAt(0);
 
   FlagsContinuation cont(kNotEqual, tbranch, fbranch);
 
   // If we can fall through to the true block, invert the branch.
   if (IsNextInAssemblyOrder(tbranch)) {
     cont.Negate();
     cont.SwapBlocks();
   }
@@ skipping 65 matching lines @@
       case IrOpcode::kInt32Sub:
         return VisitWordCompare(this, value, kIA32Cmp, &cont, false);
       case IrOpcode::kWord32And:
         return VisitWordCompare(this, value, kIA32Test, &cont, true);
       default:
         break;
     }
   }
 
   // Branch could not be combined with a compare, emit compare against 0.
-  VisitWordTest(this, value, &cont);
+  VisitCompare(this, kIA32Cmp, g.Use(value), g.TempImmediate(0), &cont);
 }
 
 
 void InstructionSelector::VisitWord32Equal(Node* const node) {
   Node* const user = node;
   FlagsContinuation cont(kEqual, node);
   Int32BinopMatcher m(user);
   if (m.right().Is(0)) {
     Node* const value = m.left().node();
     if (CanCover(user, value)) {
       switch (value->opcode()) {
         case IrOpcode::kInt32Sub:
           return VisitWordCompare(this, value, kIA32Cmp, &cont, false);
         case IrOpcode::kWord32And:
           return VisitWordCompare(this, value, kIA32Test, &cont, true);
         default:
           break;
       }
-      return VisitWordTest(this, value, &cont);
     }
   }
   return VisitWordCompare(this, node, kIA32Cmp, &cont, false);
 }
 
 
 void InstructionSelector::VisitInt32LessThan(Node* node) {
   FlagsContinuation cont(kSignedLessThan, node);
   return VisitWordCompare(this, node, kIA32Cmp, &cont, false);
 }
@@ skipping 50 matching lines @@
 
 
 void InstructionSelector::VisitFloat64LessThanOrEqual(Node* node) {
   FlagsContinuation cont(kUnorderedLessThanOrEqual, node);
   VisitFloat64Compare(this, node, &cont);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8