Revision: 3317
Author: [email protected]
Date: Tue Nov 17 02:28:04 2009
Log: Speed up charCodeAt on very large cons strings, by insisting on
flattening the strings and not trying too hard to traverse a big
cons tree from generated code.
Review URL: http://codereview.chromium.org/402008
http://code.google.com/p/v8/source/detail?r=3317
Modified:
/branches/bleeding_edge/src/ia32/codegen-ia32.cc
/branches/bleeding_edge/src/runtime.cc
/branches/bleeding_edge/src/x64/codegen-x64.cc
=======================================
--- /branches/bleeding_edge/src/ia32/codegen-ia32.cc Tue Nov 17 00:35:43
2009
+++ /branches/bleeding_edge/src/ia32/codegen-ia32.cc Tue Nov 17 02:28:04
2009
@@ -4831,6 +4831,12 @@
__ j(not_equal, &slow_case);
// ConsString.
+ // Check that the right hand side is the empty string (ie if this is
really a
+ // flat string in a cons string). If that is not the case we would
rather go
+ // to the runtime system now, to flatten the string.
+ __ mov(temp.reg(), FieldOperand(object.reg(),
ConsString::kSecondOffset));
+ __ cmp(Operand(temp.reg()),
Immediate(Handle<String>(Heap::empty_string())));
+ __ j(not_equal, &slow_case);
// Get the first of the two strings.
__ mov(object.reg(), FieldOperand(object.reg(),
ConsString::kFirstOffset));
__ jmp(&try_again_with_new_string);
=======================================
--- /branches/bleeding_edge/src/runtime.cc Wed Nov 11 07:25:51 2009
+++ /branches/bleeding_edge/src/runtime.cc Tue Nov 17 02:28:04 2009
@@ -1274,7 +1274,9 @@
// Flatten the string. If someone wants to get a char at an index
// in a cons string, it is likely that more indices will be
// accessed.
- subject->TryFlattenIfNotFlat();
+ Object* flat = subject->TryFlatten();
+ if (flat->IsFailure()) return flat;
+ subject = String::cast(flat);
if (i >= static_cast<uint32_t>(subject->length())) {
return Heap::nan_value();
}
=======================================
--- /branches/bleeding_edge/src/x64/codegen-x64.cc Tue Nov 17 00:35:43 2009
+++ /branches/bleeding_edge/src/x64/codegen-x64.cc Tue Nov 17 02:28:04 2009
@@ -3778,6 +3778,12 @@
__ j(not_equal, &slow_case);
// ConsString.
+ // Check that the right hand side is the empty string (ie if this is
really a
+ // flat string in a cons string). If that is not the case we would
rather go
+ // to the runtime system now, to flatten the string.
+ __ movq(temp.reg(), FieldOperand(object.reg(),
ConsString::kSecondOffset));
+ __ CompareRoot(temp.reg(), Heap::kEmptyStringRootIndex);
+ __ j(not_equal, &slow_case);
// Get the first of the two strings.
__ movq(object.reg(), FieldOperand(object.reg(),
ConsString::kFirstOffset));
__ jmp(&try_again_with_new_string);
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