Optionally use 31-bits SMI value for 64-bit system

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 60b0a2c14a92ae3498806d1e677b412da5598072..d190ef98c3411f62c524db4fd9eb3ed5297b5b3b 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -717,17 +717,28 @@ LInstruction* LChunkBuilder::DoShift(Token::Value op,
   HValue* right_value = instr->right();
   LOperand* right = NULL;
   int constant_value = 0;
+  bool does_deopt = false;
   if (right_value->IsConstant()) {
     HConstant* constant = HConstant::cast(right_value);
     right = chunk_->DefineConstantOperand(constant);
     constant_value = constant->Integer32Value() & 0x1f;
+    // Left shifts can deoptimize if we shift by > 0 and the result cannot be
+    // truncated to smi.
+    if (kSmiValueSize == 31 && instr->representation().IsSmi() &&
+        constant_value > 0) {
+      for (HUseIterator it(instr->uses()); !it.Done(); it.Advance()) {
+        if (!it.value()->CheckFlag(HValue::kTruncatingToSmi)) {
+          does_deopt = true;
+          break;
+        }
+      }
+    }
   } else {
     right = UseFixed(right_value, rcx);
   }
 
   // Shift operations can only deoptimize if we do a logical shift by 0 and
   // the result cannot be truncated to int32.
-  bool does_deopt = false;
   if (op == Token::SHR && constant_value == 0) {
     if (FLAG_opt_safe_uint32_operations) {
       does_deopt = !instr->CheckFlag(HInstruction::kUint32);
@@ -1855,7 +1866,8 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
       } else if (val->HasRange() && val->range()->IsInSmiRange()) {
         return DefineSameAsFirst(new(zone()) LSmiTag(value));
       } else {
-        LNumberTagI* result = new(zone()) LNumberTagI(value);
+        LOperand* temp = (kSmiValueSize == 31) ? FixedTemp(xmm1) : NULL;
+        LNumberTagI* result = new(zone()) LNumberTagI(value, temp);
         return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
       }
     } else if (to.IsSmi()) {
@@ -2088,9 +2100,15 @@ LInstruction* LChunkBuilder::DoLoadExternalArrayPointer(
 
 
 LInstruction* LChunkBuilder::DoLoadKeyed(HLoadKeyed* instr) {
-  ASSERT(instr->key()->representation().IsInteger32());
+  ASSERT((kSmiValueSize == 32 &&
+          instr->key()->representation().IsInteger32()) ||
+         (kSmiValueSize == 31 &&
+          instr->key()->representation().IsSmiOrInteger32()));
   ElementsKind elements_kind = instr->elements_kind();
-  LOperand* key = UseRegisterOrConstantAtStart(instr->key());
+  bool clobbers_key = instr->key()->representation().IsSmi();
+  LOperand* key = clobbers_key
+      ? UseTempRegister(instr->key())
+      : UseRegisterOrConstantAtStart(instr->key());
   LLoadKeyed* result = NULL;
 
   if (!instr->is_external()) {
@@ -2128,6 +2146,7 @@ LInstruction* LChunkBuilder::DoLoadKeyedGeneric(HLoadKeyedGeneric* instr) {
 
 LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
   ElementsKind elements_kind = instr->elements_kind();
+  bool clobbers_key = instr->key()->representation().IsSmi();
 
   if (!instr->is_external()) {
     ASSERT(instr->elements()->representation().IsTagged());
@@ -2139,7 +2158,8 @@ LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
     if (instr->value()->representation().IsDouble()) {
       object = UseRegisterAtStart(instr->elements());
       val = UseTempRegister(instr->value());
-      key = UseRegisterOrConstantAtStart(instr->key());
+      key = clobbers_key ? UseTempRegister(instr->key())
+          : UseRegisterOrConstantAtStart(instr->key());
     } else {
       ASSERT(instr->value()->representation().IsSmiOrTagged());
       object = UseTempRegister(instr->elements());
@@ -2148,7 +2168,8 @@ LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
         key = UseTempRegister(instr->key());
       } else {
         val = UseRegisterOrConstantAtStart(instr->value());
-        key = UseRegisterOrConstantAtStart(instr->key());
+        key = clobbers_key ? UseTempRegister(instr->key())
+            : UseRegisterOrConstantAtStart(instr->key());
       }
     }
 
@@ -2168,7 +2189,8 @@ LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
       elements_kind == EXTERNAL_FLOAT_ELEMENTS;
   LOperand* val = val_is_temp_register ? UseTempRegister(instr->value())
       : UseRegister(instr->value());
-  LOperand* key = UseRegisterOrConstantAtStart(instr->key());
+  LOperand* key = clobbers_key ? UseTempRegister(instr->key())
+      : UseRegisterOrConstantAtStart(instr->key());
   LOperand* external_pointer = UseRegister(instr->elements());
   return new(zone()) LStoreKeyed(external_pointer, key, val);
 }