Reviewers: Paul Lind, mvstanton, danno, kisg, kilvadyb,
Description:
MIPS: Improvements in lithium code generation. Recognizing if some operands
are
constants, we can often save on registers and instructions.
Port r14364 (2819e5ee)
BUG=
Please review this at https://codereview.chromium.org/14159015/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/mips/lithium-codegen-mips.cc
M src/mips/lithium-mips.cc
Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc
b/src/mips/lithium-codegen-mips.cc
index
9ae5132cf3bb8140c5b8108fb366298e2819e9cb..7a374d2de7cb5c73111221e7cecd3045cdfa7d59
100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -2873,16 +2873,24 @@ void LCodeGen::DoLoadExternalArrayPointer(
void LCodeGen::DoAccessArgumentsAt(LAccessArgumentsAt* instr) {
Register arguments = ToRegister(instr->arguments());
- Register length = ToRegister(instr->length());
- Register index = ToRegister(instr->index());
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.
- __ subu(length, length, index);
- __ Addu(length, length, Operand(1));
- __ sll(length, length, kPointerSizeLog2);
- __ Addu(at, arguments, Operand(length));
- __ lw(result, MemOperand(at, 0));
+ if (instr->length()->IsConstantOperand() &&
+ instr->index()->IsConstantOperand()) {
+ int const_index = ToInteger32(LConstantOperand::cast(instr->index()));
+ int const_length =
ToInteger32(LConstantOperand::cast(instr->length()));
+ int index = (const_length - const_index) + 1;
+ __ lw(result, MemOperand(arguments, index * kPointerSize));
+ } 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.
+ __ subu(length, length, index);
+ __ Addu(length, length, Operand(1));
+ __ sll(length, length, kPointerSizeLog2);
+ __ Addu(at, arguments, Operand(length));
+ __ lw(result, MemOperand(at, 0));
+ }
}
Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index
fb8826b7f358eb0638205fd150593077c2d64b38..41487f6d744149a3702f066707ad4f1e75ba6b66
100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -2340,8 +2340,15 @@ LInstruction*
LChunkBuilder::DoArgumentsObject(HArgumentsObject* instr) {
LInstruction* LChunkBuilder::DoAccessArgumentsAt(HAccessArgumentsAt*
instr) {
info()->MarkAsRequiresFrame();
LOperand* args = UseRegister(instr->arguments());
- LOperand* length = UseTempRegister(instr->length());
- LOperand* index = UseRegister(instr->index());
+ 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 = Use(instr->index());
+ }
return DefineAsRegister(new(zone()) LAccessArgumentsAt(args, length,
index));
}
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