HStoreNamedField for Smis optimized for x64

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 7c9949a1fad8da5b441e7ecd79d96ab41dbea073..902cea1669e29e0527f14d6a5f95eeb270fe0948 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -3946,7 +3946,8 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField* instr) {
   if (FLAG_track_fields && representation.IsSmi()) {
     if (instr->value()->IsConstantOperand()) {
       LConstantOperand* operand_value = LConstantOperand::cast(instr->value());
-      if (!IsSmiConstant(operand_value)) {
+      if (!IsInteger32Constant(operand_value) &&
+          !IsSmiConstant(operand_value)) {
         DeoptimizeIf(no_condition, instr->environment());
       }
     }
@@ -4001,6 +4002,19 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField* instr) {
     __ movq(write_register, FieldOperand(object, JSObject::kPropertiesOffset));
   }
 
+  bool kScratchRegisterContainsZero = false;
+  if (representation.IsSmi()) {
+    if (!instr->hydrogen()->can_omit_smi_tag_store()) {
+      // Clear the smi tag as we are not sure that it contains the right value.
+      __ xorl(kScratchRegister, kScratchRegister);
+      kScratchRegisterContainsZero = true;
+      __ movl(FieldOperand(write_register, offset), kScratchRegister);

[Toon Verwaest, 2013/12/09 15:51:10]

What about just shifting up the value and storing the entire 64 bits if you need
to clear? Seems like that should be at least shorter in number of instruction
bytes.

Especially if the value is constant. In that case you can just load the entire
constant in a register and write that in 1 go. You shouldn't need
kScratchRegisterContainsZero.

[Igor Sheludko, 2013/12/10 09:13:08]

Done.

+    }
+    // Deal with the upper part of the smi containing the value.
+    offset += kPointerSize / 2;
+    representation = Representation::Integer32();
+  }
+
   if (instr->value()->IsConstantOperand()) {
     LConstantOperand* operand_value = LConstantOperand::cast(instr->value());
     if (operand_value->IsRegister()) {
@@ -4009,7 +4023,11 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField* instr) {
     } else if (representation.IsInteger32()) {
       int32_t value = ToInteger32(operand_value);
       ASSERT(!instr->hydrogen()->NeedsWriteBarrier());
-      __ movl(FieldOperand(write_register, offset), Immediate(value));
+      if ((value == 0) && kScratchRegisterContainsZero) {
+        __ movl(FieldOperand(write_register, offset), kScratchRegister);
+      } else {
+        __ movl(FieldOperand(write_register, offset), Immediate(value));
+      }
     } else {
       Handle<Object> handle_value = ToHandle(operand_value);
       ASSERT(!instr->hydrogen()->NeedsWriteBarrier());