Consistently make the bounds check for AccessArgumentsAt explicit.

This has the advantage that AccessArgumentsAt itself can't deopt anymore and the
bounds check is visible for the elimination phase. Furthermore, things are
simply more consistent now, a good thing in itself. :-)

Review URL: https://codereview.chromium.org/11106012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12721 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -2164,12 +2164,10 @@ LInstruction* LChunkBuilder::DoArgumentsObject(HArgumentsObject* instr) {
 
 
 LInstruction* LChunkBuilder::DoAccessArgumentsAt(HAccessArgumentsAt* instr) {
-  LOperand* arguments = UseRegister(instr->arguments());
+  LOperand* args = UseRegister(instr->arguments());
   LOperand* length = UseTempRegister(instr->length());
   LOperand* index = UseRegister(instr->index());
-  LAccessArgumentsAt* result =
+  return DefineAsRegister(new(zone()) LAccessArgumentsAt(args, length, index));
-      new(zone()) LAccessArgumentsAt(arguments, length, index);
-  return AssignEnvironment(DefineAsRegister(result));
 }
 
 

src/arm/lithium-codegen-arm.cc

@@ -2904,14 +2904,9 @@ void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
   Register length = ToRegister(instr->length());
   Register index = ToRegister(instr->index());
   Register result = ToRegister(instr->result());
-
-  // Bailout index is not a valid argument index. Use unsigned check to get
-  // negative check for free.
-  __ sub(length, length, index, SetCC);
-  DeoptimizeIf(ls, instr->environment());
-
   // There are two words between the frame pointer and the last argument.
   // Subtracting from length accounts for one of them add one more.
+  __ sub(length, length, index);
   __ add(length, length, Operand(1));
   __ ldr(result, MemOperand(arguments, length, LSL, kPointerSizeLog2));
 }

src/hydrogen.cc

@@ -9016,8 +9016,10 @@ void HGraphBuilder::GenerateArguments(CallRuntime* call) {
   HInstruction* elements = AddInstruction(
       new(zone()) HArgumentsElements(false));
   HInstruction* length = AddInstruction(new(zone()) HArgumentsLength(elements));
+  HInstruction* checked_index =
+      AddInstruction(new(zone()) HBoundsCheck(index, length));
   HAccessArgumentsAt* result =
-      new(zone()) HAccessArgumentsAt(elements, length, index);
+      new(zone()) HAccessArgumentsAt(elements, length, checked_index);
   return ast_context()->ReturnInstruction(result, call->id());
 }
 

src/ia32/lithium-codegen-ia32.cc

@@ -2742,12 +2742,9 @@ void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
   Register length = ToRegister(instr->length());
   Operand index = ToOperand(instr->index());
   Register result = ToRegister(instr->result());
-
-  __ sub(length, index);
-  DeoptimizeIf(below_equal, instr->environment());
-
   // There are two words between the frame pointer and the last argument.
   // Subtracting from length accounts for one of them add one more.
+  __ sub(length, index);
   __ mov(result, Operand(arguments, length, times_4, kPointerSize));
 }
 

src/ia32/lithium-ia32.cc

@@ -2279,12 +2279,10 @@ LInstruction* LChunkBuilder::DoArgumentsObject(HArgumentsObject* instr) {
 
 
 LInstruction* LChunkBuilder::DoAccessArgumentsAt(HAccessArgumentsAt* instr) {
-  LOperand* arguments = UseRegister(instr->arguments());
+  LOperand* args = UseRegister(instr->arguments());
   LOperand* length = UseTempRegister(instr->length());
   LOperand* index = Use(instr->index());
-  LAccessArgumentsAt* result =
+  return DefineAsRegister(new(zone()) LAccessArgumentsAt(args, length, index));
-      new(zone()) LAccessArgumentsAt(arguments, length, index);
-  return AssignEnvironment(DefineAsRegister(result));
 }
 
 

src/mips/lithium-codegen-mips.cc

@@ -2612,14 +2612,6 @@ void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
   Register length = ToRegister(instr->length());
   Register index = ToRegister(instr->index());
   Register result = ToRegister(instr->result());
-
-  // Bailout index is not a valid argument index. Use unsigned check to get
-  // negative check for free.
-
-  // TODO(plind): Shoud be optimized to do the sub before the DeoptimizeIf(),
-  // as they do in Arm. It will save us an instruction.
-  DeoptimizeIf(ls, instr->environment(), length, Operand(index));
-
   // There are two words between the frame pointer and the last argument.
   // Subtracting from length accounts for one of them, add one more.
   __ subu(length, length, index);

src/mips/lithium-mips.cc

@@ -2106,12 +2106,10 @@ LInstruction* LChunkBuilder::DoArgumentsObject(HArgumentsObject* instr) {
 
 
 LInstruction* LChunkBuilder::DoAccessArgumentsAt(HAccessArgumentsAt* instr) {
-  LOperand* arguments = UseRegister(instr->arguments());
+  LOperand* args = UseRegister(instr->arguments());
   LOperand* length = UseTempRegister(instr->length());
   LOperand* index = UseRegister(instr->index());
-  LAccessArgumentsAt* result =
+  return DefineAsRegister(new(zone()) LAccessArgumentsAt(args, length, index));
-      new(zone()) LAccessArgumentsAt(arguments, length, index);
-  return AssignEnvironment(DefineAsRegister(result));
 }
 
 

src/x64/lithium-codegen-x64.cc

@@ -2601,16 +2601,13 @@ void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
   Register arguments = ToRegister(instr->arguments());
   Register length = ToRegister(instr->length());
   Register result = ToRegister(instr->result());
-
+  // There are two words between the frame pointer and the last argument.
+  // Subtracting from length accounts for one of them add one more.
   if (instr->index()->IsRegister()) {
     __ subl(length, ToRegister(instr->index()));
   } else {
     __ subl(length, ToOperand(instr->index()));
   }
-  DeoptimizeIf(below_equal, instr->environment());
-
-  // There are two words between the frame pointer and the last argument.
-  // Subtracting from length accounts for one of them add one more.
   __ movq(result, Operand(arguments, length, times_pointer_size, kPointerSize));
 }
 

src/x64/lithium-x64.cc

@@ -2167,12 +2167,10 @@ LInstruction* LChunkBuilder::DoArgumentsObject(HArgumentsObject* instr) {
 
 
 LInstruction* LChunkBuilder::DoAccessArgumentsAt(HAccessArgumentsAt* instr) {
-  LOperand* arguments = UseRegister(instr->arguments());
+  LOperand* args = UseRegister(instr->arguments());
   LOperand* length = UseTempRegister(instr->length());
   LOperand* index = Use(instr->index());
-  LAccessArgumentsAt* result =
+  return DefineAsRegister(new(zone()) LAccessArgumentsAt(args, length, index));
-      new(zone()) LAccessArgumentsAt(arguments, length, index);
-  return AssignEnvironment(DefineAsRegister(result));
 }