Improve implementation of HSeqStringSetChar.

src/ia32/lithium-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 562 matching lines @@
 }
 
 
 LOperand* LChunkBuilder::UseOrConstantAtStart(HValue* value) {
   return CanBeImmediateConstant(value)
       ? chunk_->DefineConstantOperand(HConstant::cast(value))
       : UseAtStart(value);
 }
 
 
+LOperand* LChunkBuilder::UseFixedOrConstant(HValue* value,
+                                            Register fixed_register) {
+  return CanBeImmediateConstant(value)
+      ? chunk_->DefineConstantOperand(HConstant::cast(value))
+      : UseFixed(value, fixed_register);
+}
+
+
 LOperand* LChunkBuilder::UseRegisterOrConstant(HValue* value) {
   return CanBeImmediateConstant(value)
       ? chunk_->DefineConstantOperand(HConstant::cast(value))
       : UseRegister(value);
 }
 
 
 LOperand* LChunkBuilder::UseRegisterOrConstantAtStart(HValue* value) {
   return CanBeImmediateConstant(value)
       ? chunk_->DefineConstantOperand(HConstant::cast(value))
@@ skipping 1266 matching lines @@
 
 LInstruction* LChunkBuilder::DoDateField(HDateField* instr) {
   LOperand* date = UseFixed(instr->value(), eax);
   LDateField* result =
       new(zone()) LDateField(date, FixedTemp(ecx), instr->index());
   return MarkAsCall(DefineFixed(result, eax), instr, CAN_DEOPTIMIZE_EAGERLY);
 }
 
 
 LInstruction* LChunkBuilder::DoSeqStringSetChar(HSeqStringSetChar* instr) {
-  LOperand* string = UseRegister(instr->string());
-  LOperand* index = UseRegister(instr->index());
-  ASSERT(ecx.is_byte_register());
-  LOperand* value = UseFixed(instr->value(), ecx);
-  LSeqStringSetChar* result =
-      new(zone()) LSeqStringSetChar(instr->encoding(), string, index, value);
-  return DefineSameAsFirst(result);
+  LOperand* string = UseRegisterAtStart(instr->string());
+  LOperand* index = UseRegisterOrConstantAtStart(instr->index());
+  LOperand* value = (instr->encoding() == String::ONE_BYTE_ENCODING)
+      ? UseFixedOrConstant(instr->value(), eax)

[Yang, 2013/11/06 09:55:09]

Why does this have to be fixed to eax, why not UseRegisterOrConstant?

[Benedikt Meurer, 2013/11/06 10:06:36]

Because mov_b() requires a byte register.

+      : UseRegisterOrConstantAtStart(instr->value());
+  return new(zone()) LSeqStringSetChar(string, index, value);
 }
 
 
 LInstruction* LChunkBuilder::DoBoundsCheck(HBoundsCheck* instr) {
   return AssignEnvironment(new(zone()) LBoundsCheck(
       UseRegisterOrConstantAtStart(instr->index()),
       UseAtStart(instr->length())));
 }
 
 
@@ skipping 850 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32