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Flatten cons string for single character substrings.

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For substrings of non-flat cons strings, we bail out
to runtime. For single character substrings, we forget
to flatten it. This causes successive bailouts.

R=bmeurer@chromium.org
BUG=323041
LOG=Y

Review URL: https://codereview.chromium.org/88173002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18081 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
yangguo@chromium.org 2013-11-26 14:21:46 +00:00
parent 57a0c1fec3
commit 4240cd2506
2 changed files with 7 additions and 9 deletions
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12
src/heap.cc
View File

@ -3968,7 +3968,12 @@ MaybeObject* Heap::AllocateSubString(String* buffer,
int length = end - start;
if (length <= 0) {
return empty_string();
} else if (length == 1) {
}
// Make an attempt to flatten the buffer to reduce access time.
buffer = buffer->TryFlattenGetString();
if (length == 1) {
return LookupSingleCharacterStringFromCode(buffer->Get(start));
} else if (length == 2) {
// Optimization for 2-byte strings often used as keys in a decompression
@ -3979,9 +3984,6 @@ MaybeObject* Heap::AllocateSubString(String* buffer,
return MakeOrFindTwoCharacterString(this, c1, c2);
}
// Make an attempt to flatten the buffer to reduce access time.
buffer = buffer->TryFlattenGetString();
if (!FLAG_string_slices ||
!buffer->IsFlat() ||
length < SlicedString::kMinLength ||
@ -4981,7 +4983,7 @@ MaybeObject* Heap::ReinitializeJSGlobalProxy(JSFunction* constructor,
MaybeObject* Heap::AllocateStringFromOneByte(Vector<const uint8_t> string,
PretenureFlag pretenure) {
PretenureFlag pretenure) {
int length = string.length();
if (length == 1) {
return Heap::LookupSingleCharacterStringFromCode(string[0]);

4
src/runtime.cc
View File

@ -4463,10 +4463,6 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_SubString) {
RUNTIME_ASSERT(start >= 0);
RUNTIME_ASSERT(end <= value->length());
isolate->counters()->sub_string_runtime()->Increment();
if (end - start == 1) {
return isolate->heap()->LookupSingleCharacterStringFromCode(
value->Get(start));
}
return value->SubString(start, end);
}