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Unified Diff: src/x64/code-stubs-x64.cc

Issue 6927044: Extract common code in string compare loops. (Closed)
Patch Set: Created 9 years, 8 months ago
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Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 319b1050b9ba1aa36b6bfe186f6c1310952d110d..8cd9194607c845ffeaaed5b57d21dbecba382db4 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -4523,26 +4523,9 @@ void StringCompareStub::GenerateFlatAsciiStringEquals(MacroAssembler* masm,
// Compare characters.
__ bind(&compare_chars);
-
- // Change index to run from -length to -1 by adding length to string
- // start. This means that loop ends when index reaches zero, which
- // doesn't need an additional compare.
- __ SmiToInteger32(length, length);
- __ lea(left,
- FieldOperand(left, length, times_1, SeqAsciiString::kHeaderSize));
- __ lea(right,
- FieldOperand(right, length, times_1, SeqAsciiString::kHeaderSize));
- __ neg(length);
- Register index = length; // index = -length;
-
- // Compare loop.
- NearLabel strings_not_equal, loop;
- __ bind(&loop);
- __ movb(scratch2, Operand(left, index, times_1, 0));
- __ cmpb(scratch2, Operand(right, index, times_1, 0));
- __ j(not_equal, &strings_not_equal);
- __ addq(index, Immediate(1));
- __ j(not_zero, &loop);
+ NearLabel strings_not_equal;
+ GenerateAsciiCharsCompareLoop(masm, left, right, length, scratch2,
+ &strings_not_equal);
// Characters are equal.
__ Move(rax, Smi::FromInt(EQUAL));
@@ -4589,35 +4572,11 @@ void StringCompareStub::GenerateCompareFlatAsciiStrings(MacroAssembler* masm,
__ SmiTest(min_length);
__ j(zero, &compare_lengths);
- __ SmiToInteger32(min_length, min_length);
-
- // Registers scratch2 and scratch3 are free.
+ // Compare loop.
NearLabel result_not_equal;
- Label loop;
- {
- // Check characters 0 .. min_length - 1 in a loop.
- // Use scratch3 as loop index, min_length as limit and scratch2
- // for computation.
- const Register index = scratch3;
- __ Set(index, 0); // Index into strings.
- __ bind(&loop);
- // Compare characters.
- // TODO(lrn): Could we load more than one character at a time?
- __ movb(scratch2, FieldOperand(left,
- index,
- times_1,
- SeqAsciiString::kHeaderSize));
- // Increment index and use -1 modifier on next load to give
- // the previous load extra time to complete.
- __ addl(index, Immediate(1));
- __ cmpb(scratch2, FieldOperand(right,
- index,
- times_1,
- SeqAsciiString::kHeaderSize - 1));
- __ j(not_equal, &result_not_equal);
- __ cmpl(index, min_length);
- __ j(not_equal, &loop);
- }
+ GenerateAsciiCharsCompareLoop(masm, left, right, min_length, scratch2,
+ &result_not_equal);
+
// Completed loop without finding different characters.
// Compare lengths (precomputed).
__ bind(&compare_lengths);
@@ -4644,6 +4603,35 @@ void StringCompareStub::GenerateCompareFlatAsciiStrings(MacroAssembler* masm,
}
+void StringCompareStub::GenerateAsciiCharsCompareLoop(
+ MacroAssembler* masm,
+ Register left,
+ Register right,
+ Register length,
+ Register scratch,
+ NearLabel* chars_not_equal) {
+ // Change index to run from -length to -1 by adding length to string
+ // start. This means that loop ends when index reaches zero, which
+ // doesn't need an additional compare.
+ __ SmiToInteger32(length, length);
+ __ lea(left,
+ FieldOperand(left, length, times_1, SeqAsciiString::kHeaderSize));
+ __ lea(right,
+ FieldOperand(right, length, times_1, SeqAsciiString::kHeaderSize));
+ __ neg(length);
+ Register index = length; // index = -length;
+
+ // Compare loop.
+ NearLabel loop;
+ __ bind(&loop);
+ __ movb(scratch, Operand(left, index, times_1, 0));
+ __ cmpb(scratch, Operand(right, index, times_1, 0));
+ __ j(not_equal, chars_not_equal);
+ __ addq(index, Immediate(1));
+ __ j(not_zero, &loop);
+}
+
+
void StringCompareStub::Generate(MacroAssembler* masm) {
Label runtime;
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