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Add special case of taking a substring that is the entire string to stub.

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Review URL: http://codereview.chromium.org/2800027

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4951 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
lrn@chromium.org 2010-06-25 11:24:41 +00:00
parent faaf524445
commit f0529878d1
2 changed files with 11 additions and 1 deletions
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6
src/ia32/codegen-ia32.cc
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@ -13295,6 +13295,9 @@ void SubStringStub::Generate(MacroAssembler* masm) {
__ test(edx, Immediate(kSmiTagMask));
__ j(not_zero, &runtime);
__ sub(ecx, Operand(edx));
__ cmp(ecx, FieldOperand(eax, String::kLengthOffset));
Label return_eax;
__ j(equal, &return_eax);
// Special handling of sub-strings of length 1 and 2. One character strings
// are handled in the runtime system (looked up in the single character
// cache). Two character strings are looked for in the symbol cache.
@ -13399,12 +13402,15 @@ void SubStringStub::Generate(MacroAssembler* masm) {
// esi: character of sub string start
StringHelper::GenerateCopyCharactersREP(masm, edi, esi, ecx, ebx, false);
__ mov(esi, edx); // Restore esi.
__ bind(&return_eax);
__ IncrementCounter(&Counters::sub_string_native, 1);
__ ret(3 * kPointerSize);
// Just jump to runtime to create the sub string.
__ bind(&runtime);
__ TailCallRuntime(Runtime::kSubString, 3, 1);
}

6
src/x64/codegen-x64.cc
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@ -11574,7 +11574,9 @@ void SubStringStub::Generate(MacroAssembler* masm) {
__ JumpIfNotBothPositiveSmi(rcx, rdx, &runtime);
__ SmiSub(rcx, rcx, rdx, NULL); // Overflow doesn't happen.
__ j(negative, &runtime);
__ cmpq(FieldOperand(rax, String::kLengthOffset), rcx);
Label return_rax;
__ j(equal, &return_rax);
// Special handling of sub-strings of length 1 and 2. One character strings
// are handled in the runtime system (looked up in the single character
// cache). Two character strings are looked for in the symbol cache.
@ -11677,6 +11679,8 @@ void SubStringStub::Generate(MacroAssembler* masm) {
// rsi: character of sub string start
StringHelper::GenerateCopyCharactersREP(masm, rdi, rsi, rcx, false);
__ movq(rsi, rdx); // Restore esi.
__ bind(&return_rax);
__ IncrementCounter(&Counters::sub_string_native, 1);
__ ret(kArgumentsSize);