Reviewers: Erik Corry,
Message:
Please take a look.
The performance regression was introduced in r9027 when I committed my
tentative
implementation for sliced strings. In particular, the bug was introduced in
line
4500:
http://code.google.com/p/v8/source/diff?spec=svn9027&r=9027&format=side&path=/branches/bleeding_edge/src/arm/code-stubs-arm.cc
http://codereview.chromium.org/7824033/diff/1/src/arm/code-stubs-arm.cc
File src/arm/code-stubs-arm.cc (left):
http://codereview.chromium.org/7824033/diff/1/src/arm/code-stubs-arm.cc#oldcode4530
src/arm/code-stubs-arm.cc:4530: __ b(ne, &runtime);
even though subject is not the result of the regexp, comparing it with
SUCCESS, FAILURE and EXCEPTION would eventually result in a jump into
runtime, so that the final result is correct, but performance takes a
hit.
http://codereview.chromium.org/7824033/diff/1/src/arm/code-stubs-arm.cc
File src/arm/code-stubs-arm.cc (right):
http://codereview.chromium.org/7824033/diff/1/src/arm/code-stubs-arm.cc#newcode4490
src/arm/code-stubs-arm.cc:4490: __ ldr(subject, MemOperand(fp,
kSubjectOffset + 2 * kPointerSize));
the underlying subject string is no longer needed, and can be replaced
by the original subject string.
http://codereview.chromium.org/7824033/diff/1/src/arm/code-stubs-arm.cc#newcode4523
src/arm/code-stubs-arm.cc:4523: __ cmp(r0,
Operand(NativeRegExpMacroAssembler::SUCCESS));
not subject (r4) but r0 is the return value of the regexp.
Description:
Fixed performance regression in v8 regexp benchmark on ARM.
Please review this at http://codereview.chromium.org/7824033/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/arm/code-stubs-arm.cc
Index: src/arm/code-stubs-arm.cc
diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index
f6b87c38e58f0b4cd403bb15c835e01fe59ea6d0..c8d3edd033c8f9fdbb955575437aa47dc16e6915
100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -4487,7 +4487,7 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
// frame. Therefore we have to use fp, which points exactly to two
pointer
// sizes below the previous sp. (Because creating a new stack frame
pushes
// the previous fp onto the stack and moves up sp by 2 * kPointerSize.)
- __ ldr(r0, MemOperand(fp, kSubjectOffset + 2 * kPointerSize));
+ __ ldr(subject, MemOperand(fp, kSubjectOffset + 2 * kPointerSize));
// If slice offset is not 0, load the length from the original sliced
string.
// Argument 4, r3: End of string data
// Argument 3, r2: Start of string data
@@ -4495,7 +4495,7 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
__ add(r9, r8, Operand(r9, LSL, r3));
__ add(r2, r9, Operand(r1, LSL, r3));
- __ ldr(r8, FieldMemOperand(r0, String::kLengthOffset));
+ __ ldr(r8, FieldMemOperand(subject, String::kLengthOffset));
__ mov(r8, Operand(r8, ASR, kSmiTagSize));
__ add(r3, r9, Operand(r8, LSL, r3));
@@ -4503,7 +4503,7 @@ void RegExpExecStub::Generate(MacroAssembler* masm) {
// Already there
// Argument 1 (r0): Subject string.
- // Already there
+ __ mov(r0, subject);
// Locate the code entry and call it.
__ add(r7, r7, Operand(Code::kHeaderSize - kHeapObjectTag));
@@ -4520,12 +4520,12 @@ void RegExpExecStub::Generate(MacroAssembler* masm)
{
// Check the result.
Label success;
- __ cmp(subject, Operand(NativeRegExpMacroAssembler::SUCCESS));
+ __ cmp(r0, Operand(NativeRegExpMacroAssembler::SUCCESS));
__ b(eq, &success);
Label failure;
- __ cmp(subject, Operand(NativeRegExpMacroAssembler::FAILURE));
+ __ cmp(r0, Operand(NativeRegExpMacroAssembler::FAILURE));
__ b(eq, &failure);
- __ cmp(subject, Operand(NativeRegExpMacroAssembler::EXCEPTION));
+ __ cmp(r0, Operand(NativeRegExpMacroAssembler::EXCEPTION));
// If not exception it can only be retry. Handle that in the runtime
system.
__ b(ne, &runtime);
// Result must now be exception. If there is no pending exception
already a
@@ -4537,18 +4537,18 @@ void RegExpExecStub::Generate(MacroAssembler* masm)
{
__ mov(r2,
Operand(ExternalReference(Isolate::k_pending_exception_address,
isolate)));
__ ldr(r0, MemOperand(r2, 0));
- __ cmp(subject, r1);
+ __ cmp(r0, r1);
__ b(eq, &runtime);
__ str(r1, MemOperand(r2, 0)); // Clear pending exception.
// Check if the exception is a termination. If so, throw as uncatchable.
__ LoadRoot(ip, Heap::kTerminationExceptionRootIndex);
- __ cmp(subject, ip);
+ __ cmp(r0, ip);
Label termination_exception;
__ b(eq, &termination_exception);
- __ Throw(subject); // Expects thrown value in r0.
+ __ Throw(r0); // Expects thrown value in r0.
__ bind(&termination_exception);
__ ThrowUncatchable(TERMINATION, r0); // Expects thrown value in r0.
--
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