Bias commutative single-use register inputs and support lea adds

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 97041dec702f00f853a59b3ec0ebd7ed893d12b3..e5ba3c64510a552d2234e71a1e4c2bb67274ef99 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -834,8 +834,8 @@ LInstruction* LChunkBuilder::DoArithmeticD(Token::Value op,
   ASSERT(instr->left()->representation().IsDouble());
   ASSERT(instr->right()->representation().IsDouble());
   ASSERT(op != Token::MOD);
-  LOperand* left = UseRegisterAtStart(instr->left());
-  LOperand* right = UseRegisterAtStart(instr->right());
+  LOperand* left = UseRegisterAtStart(instr->BetterLeftOperand());
+  LOperand* right = UseRegisterAtStart(instr->BetterRightOperand());
   LArithmeticD* result = new(zone()) LArithmeticD(op, left, right);
   return DefineSameAsFirst(result);
 }
@@ -1392,8 +1392,8 @@ LInstruction* LChunkBuilder::DoBitwise(HBitwise* instr) {
     ASSERT(instr->left()->representation().IsInteger32());
     ASSERT(instr->right()->representation().IsInteger32());
 
-    LOperand* left = UseRegisterAtStart(instr->LeastConstantOperand());
-    LOperand* right = UseOrConstantAtStart(instr->MostConstantOperand());
+    LOperand* left = UseRegisterAtStart(instr->BetterLeftOperand());
+    LOperand* right = UseOrConstantAtStart(instr->BetterRightOperand());
     return DefineSameAsFirst(new(zone()) LBitI(left, right));
   } else {
     ASSERT(instr->representation().IsTagged());
@@ -1560,8 +1560,8 @@ LInstruction* LChunkBuilder::DoMul(HMul* instr) {
   if (instr->representation().IsInteger32()) {
     ASSERT(instr->left()->representation().IsInteger32());
     ASSERT(instr->right()->representation().IsInteger32());
-    LOperand* left = UseRegisterAtStart(instr->LeastConstantOperand());
-    LOperand* right = UseOrConstant(instr->MostConstantOperand());
+    LOperand* left = UseRegisterAtStart(instr->BetterLeftOperand());
+    LOperand* right = UseOrConstant(instr->BetterRightOperand());
     LOperand* temp = NULL;
     if (instr->CheckFlag(HValue::kBailoutOnMinusZero)) {
       temp = TempRegister();
@@ -1604,13 +1604,24 @@ LInstruction* LChunkBuilder::DoSub(HSub* instr) {
 
 LInstruction* LChunkBuilder::DoAdd(HAdd* instr) {
   if (instr->representation().IsInteger32()) {
+    // Check to see if it would be advantageous to use an lea instruction rather
+    // than an add. This is the case when no overflow check is needed and there
+    // are multiple uses of the add's inputs, so using a 3-register add will
+    // preserve all input values for later uses.
+    bool use_lea = LAddI::UseLea(instr);
     ASSERT(instr->left()->representation().IsInteger32());
     ASSERT(instr->right()->representation().IsInteger32());
-    LOperand* left = UseRegisterAtStart(instr->LeastConstantOperand());
-    LOperand* right = UseOrConstantAtStart(instr->MostConstantOperand());
+    LOperand* left = UseRegisterAtStart(instr->BetterLeftOperand());
+    HValue* right_candidate = instr->BetterRightOperand();
+    LOperand* right = use_lea
+        ? UseRegisterOrConstantAtStart(right_candidate)
+        : UseOrConstantAtStart(right_candidate);
     LAddI* add = new(zone()) LAddI(left, right);
-    LInstruction* result = DefineSameAsFirst(add);
-    if (instr->CheckFlag(HValue::kCanOverflow)) {
+    bool can_overflow = instr->CheckFlag(HValue::kCanOverflow);
+    LInstruction* result = use_lea
+        ? DefineAsRegister(add)
+        : DefineSameAsFirst(add);
+    if (can_overflow) {
       result = AssignEnvironment(result);
     }
     return result;
@@ -1629,8 +1640,8 @@ LInstruction* LChunkBuilder::DoMathMinMax(HMathMinMax* instr) {
   if (instr->representation().IsInteger32()) {
     ASSERT(instr->left()->representation().IsInteger32());
     ASSERT(instr->right()->representation().IsInteger32());
-    left = UseRegisterAtStart(instr->LeastConstantOperand());
-    right = UseOrConstantAtStart(instr->MostConstantOperand());
+    left = UseRegisterAtStart(instr->BetterLeftOperand());
+    right = UseOrConstantAtStart(instr->BetterRightOperand());
   } else {
     ASSERT(instr->representation().IsDouble());
     ASSERT(instr->left()->representation().IsDouble());