Reviewers: ulan, danno,
Description:
ARM: Optimize AccessArgumentsAt
Optimize register constraints and code generated for AccessArgumentsAt
Lithium instruction.
TEST=none
BUG=
Please review this at https://codereview.chromium.org/78093004/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+28, -20 lines):
M src/arm/lithium-arm.cc
M src/arm/lithium-codegen-arm.cc
Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index
a6644af5ef78a605a9beb003dfd93228339dba32..60f577eb42d06ea0a4ca0c9195d1d0d41ae08261
100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -2554,15 +2554,8 @@ LInstruction*
LChunkBuilder::DoCapturedObject(HCapturedObject* instr) {
LInstruction* LChunkBuilder::DoAccessArgumentsAt(HAccessArgumentsAt*
instr) {
info()->MarkAsRequiresFrame();
LOperand* args = UseRegister(instr->arguments());
- LOperand* length;
- LOperand* index;
- if (instr->length()->IsConstant() && instr->index()->IsConstant()) {
- length = UseRegisterOrConstant(instr->length());
- index = UseOrConstant(instr->index());
- } else {
- length = UseTempRegister(instr->length());
- index = UseRegisterAtStart(instr->index());
- }
+ LOperand* length = UseRegisterOrConstantAtStart(instr->length());
+ LOperand* index = UseRegisterOrConstantAtStart(instr->index());
return DefineAsRegister(new(zone()) LAccessArgumentsAt(args, length,
index));
}
Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index
0d4d805acbed5ab227d64cf2a6fd7c85635ace07..c63118ba0d20ee800c419c35f0fcb9038a9cd265
100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -3216,20 +3216,35 @@ void LCodeGen::DoLoadExternalArrayPointer(
void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
Register arguments = ToRegister(instr->arguments());
Register result = ToRegister(instr->result());
- if (instr->length()->IsConstantOperand() &&
- instr->index()->IsConstantOperand()) {
- int const_index = ToInteger32(LConstantOperand::cast(instr->index()));
+ // 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->length()->IsConstantOperand()) {
int const_length =
ToInteger32(LConstantOperand::cast(instr->length()));
- int index = (const_length - const_index) + 1;
- __ ldr(result, MemOperand(arguments, index * kPointerSize));
- } else {
+ if (instr->index()->IsConstantOperand()) {
+ int const_index =
ToInteger32(LConstantOperand::cast(instr->index()));
+ int index = (const_length - const_index) + 1;
+ __ ldr(result, MemOperand(arguments, index * kPointerSize));
+ } else {
+ Register index = ToRegister(instr->index());
+ __ rsb(result, index, Operand(const_length + 1));
+ __ ldr(result, MemOperand(arguments, result, LSL, kPointerSizeLog2));
+ }
+ } else if (instr->index()->IsConstantOperand()) {
+ Register length = ToRegister(instr->length());
+ int const_index =
ToInteger32(LConstantOperand::cast(instr->index()));
+ int loc = const_index - 1;
+ if (loc != 0) {
+ __ sub(result, length, Operand(loc));
+ __ ldr(result, MemOperand(arguments, result, LSL,
kPointerSizeLog2));
+ } else {
+ __ ldr(result, MemOperand(arguments, length, LSL,
kPointerSizeLog2));
+ }
+ } else {
Register length = ToRegister(instr->length());
Register index = ToRegister(instr->index());
- // 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));
+ __ sub(result, length, index);
+ __ add(result, result, Operand(1));
+ __ ldr(result, MemOperand(arguments, result, LSL, kPointerSizeLog2));
}
}
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