[x86] Several small performance improvements.

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

Index: src/compiler/ia32/instruction-selector-ia32.cc
diff --git a/src/compiler/ia32/instruction-selector-ia32.cc b/src/compiler/ia32/instruction-selector-ia32.cc
index add0a3f2b1fc17f47ffc1926844fadaadedb303f..99685f14e58ff106ead5107fc1886f5f6e6b1cdf 100644
--- a/src/compiler/ia32/instruction-selector-ia32.cc
+++ b/src/compiler/ia32/instruction-selector-ia32.cc
@@ -259,7 +259,18 @@ static void VisitBinop(InstructionSelector* selector, Node* node,
   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 {
@@ -674,13 +685,6 @@ static inline void VisitWordCompare(InstructionSelector* selector, Node* node,
 }
 
 
-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) {
@@ -694,7 +698,7 @@ static void VisitFloat64Compare(InstructionSelector* selector, Node* node,
 
 void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
                                       BasicBlock* fbranch) {
-  OperandGenerator g(this);
+  IA32OperandGenerator g(this);
   Node* user = branch;
   Node* value = branch->InputAt(0);
 
@@ -780,7 +784,7 @@ void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
   }
 
   // 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);
 }
 
 
@@ -799,7 +803,6 @@ void InstructionSelector::VisitWord32Equal(Node* const node) {
         default:
           break;
       }
-      return VisitWordTest(this, value, &cont);
     }
   }
   return VisitWordCompare(this, node, kIA32Cmp, &cont, false);