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

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Port r10012 (09c6bcba81).

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

BUG=
TEST=

Review URL: http://codereview.chromium.org/8585041

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10027 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
yangguo@chromium.org 2011-11-18 09:13:01 +00:00
parent 0bd29a1af6
commit f0878c8424
1 changed files with 5 additions and 7 deletions
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12
src/mips/code-stubs-mips.cc
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@ -6026,15 +6026,13 @@ void SubStringStub::Generate(MacroAssembler* masm) {
// a3: from index (untagged smi)
// t2 (a.k.a. to): to (smi)
// t3 (a.k.a. from): from offset (smi)
Label allocate_slice, sliced_string, seq_string;
STATIC_ASSERT(kSeqStringTag == 0);
__ And(t4, a1, Operand(kStringRepresentationMask));
__ Branch(&seq_string, eq, t4, Operand(zero_reg));
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);
__ And(t4, a1, Operand(kIsIndirectStringMask));
// External string. Jump to runtime.
__ Branch(&sub_string_runtime, eq, t4, Operand(zero_reg));
__ Branch(&seq_or_external_string, eq, t4, Operand(zero_reg));
__ And(t4, a1, Operand(kSlicedNotConsMask));
__ Branch(&sliced_string, ne, t4, Operand(zero_reg));
@ -6052,8 +6050,8 @@ void SubStringStub::Generate(MacroAssembler* masm) {
__ lw(t1, FieldMemOperand(v0, 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(t1, v0);
__ bind(&allocate_slice);