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Change generated code for substring not to bail out to runtime system.

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There is no need to bail out to runtime system when creating sliced strings of external strings since the string content is unimportant.

Review URL: http://codereview.chromium.org/8513016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10012 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
yangguo@chromium.org 2011-11-17 08:40:40 +00:00
parent 08f69647d3
commit 85b693c9e8
3 changed files with 15 additions and 24 deletions
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13
src/arm/code-stubs-arm.cc
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@ -5815,15 +5815,12 @@ void SubStringStub::Generate(MacroAssembler* masm) {
// r3: from index (untagged smi)
// r6 (a.k.a. to): to (smi)
// r7 (a.k.a. from): from offset (smi)
Label allocate_slice, sliced_string, seq_string;
STATIC_ASSERT(kSeqStringTag == 0);
__ tst(r1, Operand(kStringRepresentationMask));
__ b(eq, &seq_string);
Label allocate_slice, sliced_string, seq_or_external_string;
// If the string is not indirect, it can only be sequential or external.
STATIC_ASSERT(kIsIndirectStringMask == (kSlicedStringTag & kConsStringTag));
STATIC_ASSERT(kIsIndirectStringMask != 0);
__ tst(r1, Operand(kIsIndirectStringMask));
// External string. Jump to runtime.
__ b(eq, &runtime);
__ b(eq, &seq_or_external_string);
__ tst(r1, Operand(kSlicedNotConsMask));
__ b(ne, &sliced_string);
@ -5842,8 +5839,8 @@ void SubStringStub::Generate(MacroAssembler* masm) {
__ ldr(r5, FieldMemOperand(r0, SlicedString::kParentOffset));
__ jmp(&allocate_slice);
__ bind(&seq_string);
// Sequential string. Just move string to the right register.
__ bind(&seq_or_external_string);
// Sequential or external string. Just move string to the correct register.
__ mov(r5, r0);
__ bind(&allocate_slice);

13
src/ia32/code-stubs-ia32.cc
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@ -5973,18 +5973,15 @@ void SubStringStub::Generate(MacroAssembler* masm) {
// ebx: instance type
// ecx: sub string length
// edx: from index (smi)
Label allocate_slice, sliced_string, seq_string;
Label allocate_slice, sliced_string, seq_or_external_string;
__ cmp(ecx, SlicedString::kMinLength);
// Short slice. Copy instead of slicing.
__ j(less, &copy_routine);
STATIC_ASSERT(kSeqStringTag == 0);
__ test(ebx, Immediate(kStringRepresentationMask));
__ j(zero, &seq_string, Label::kNear);
// If the string is not indirect, it can only be sequential or external.
STATIC_ASSERT(kIsIndirectStringMask == (kSlicedStringTag & kConsStringTag));
STATIC_ASSERT(kIsIndirectStringMask != 0);
__ test(ebx, Immediate(kIsIndirectStringMask));
// External string. Jump to runtime.
__ j(zero, &runtime);
__ j(zero, &seq_or_external_string, Label::kNear);
Factory* factory = masm->isolate()->factory();
__ test(ebx, Immediate(kSlicedNotConsMask));
@ -6002,8 +5999,8 @@ void SubStringStub::Generate(MacroAssembler* masm) {
__ mov(edi, FieldOperand(eax, SlicedString::kParentOffset));
__ jmp(&allocate_slice, Label::kNear);
__ bind(&seq_string);
// Sequential string. Just move string to the right register.
__ bind(&seq_or_external_string);
// Sequential or external string. Just move string to the correct register.
__ mov(edi, eax);
__ bind(&allocate_slice);

13
src/x64/code-stubs-x64.cc
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@ -4912,18 +4912,15 @@ void SubStringStub::Generate(MacroAssembler* masm) {
// rbx: instance type
// rcx: sub string length
// rdx: from index (smi)
Label allocate_slice, sliced_string, seq_string;
Label allocate_slice, sliced_string, seq_or_external_string;
__ cmpq(rcx, Immediate(SlicedString::kMinLength));
// Short slice. Copy instead of slicing.
__ j(less, &copy_routine);
STATIC_ASSERT(kSeqStringTag == 0);
__ testb(rbx, Immediate(kStringRepresentationMask));
__ j(zero, &seq_string, Label::kNear);
// If the string is not indirect, it can only be sequential or external.
STATIC_ASSERT(kIsIndirectStringMask == (kSlicedStringTag & kConsStringTag));
STATIC_ASSERT(kIsIndirectStringMask != 0);
__ testb(rbx, Immediate(kIsIndirectStringMask));
// External string. Jump to runtime.
__ j(zero, &runtime);
__ j(zero, &seq_or_external_string, Label::kNear);
__ testb(rbx, Immediate(kSlicedNotConsMask));
__ j(not_zero, &sliced_string, Label::kNear);
@ -4940,8 +4937,8 @@ void SubStringStub::Generate(MacroAssembler* masm) {
__ movq(rdi, FieldOperand(rax, SlicedString::kParentOffset));
__ jmp(&allocate_slice, Label::kNear);
__ bind(&seq_string);
// Sequential string. Just move string to the right register.
__ bind(&seq_or_external_string);
// Sequential or external string. Just move string to the correct register.
__ movq(rdi, rax);
__ bind(&allocate_slice);