Reviewers: Yang,
Message:
Yang.
please help to review this porting patch for X87.
thanks
Description:
X87: Simplify string copy in SubStringStub.
port r21756.
original commit message:
The optimizations are unnecessary since the maximum
string length they operate on is currently 12.
R=bmeu...@chromium.org
BUG=352155
LOG=N
Please review this at https://codereview.chromium.org/326353002/
SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/
Affected files (+26, -57 lines):
M src/x87/code-stubs-x87.h
M src/x87/code-stubs-x87.cc
Index: src/x87/code-stubs-x87.cc
===================================================================
--- src/x87/code-stubs-x87.cc (revision 21759)
+++ src/x87/code-stubs-x87.cc (working copy)
@@ -2855,18 +2855,12 @@
}
-void StringHelper::GenerateCopyCharactersREP(MacroAssembler* masm,
- Register dest,
- Register src,
- Register count,
- Register scratch,
- bool ascii) {
- // Copy characters using rep movs of doublewords.
- // The destination is aligned on a 4 byte boundary because we are
- // copying to the beginning of a newly allocated string.
- ASSERT(dest.is(edi)); // rep movs destination
- ASSERT(src.is(esi)); // rep movs source
- ASSERT(count.is(ecx)); // rep movs count
+void StringHelper::GenerateCopyCharacters(MacroAssembler* masm,
+ Register dest,
+ Register src,
+ Register count,
+ Register scratch,
+ String::Encoding encoding) {
ASSERT(!scratch.is(dest));
ASSERT(!scratch.is(src));
ASSERT(!scratch.is(count));
@@ -2877,38 +2871,17 @@
__ j(zero, &done);
// Make count the number of bytes to copy.
- if (!ascii) {
+ if (encoding == String::TWO_BYTE_ENCODING) {
__ shl(count, 1);
}
- // Don't enter the rep movs if there are less than 4 bytes to copy.
- Label last_bytes;
- __ test(count, Immediate(~3));
- __ j(zero, &last_bytes, Label::kNear);
-
- // Copy from edi to esi using rep movs instruction.
- __ mov(scratch, count);
- __ sar(count, 2); // Number of doublewords to copy.
- __ cld();
- __ rep_movs();
-
- // Find number of bytes left.
- __ mov(count, scratch);
- __ and_(count, 3);
-
- // Check if there are more bytes to copy.
- __ bind(&last_bytes);
- __ test(count, count);
- __ j(zero, &done);
-
- // Copy remaining characters.
Label loop;
__ bind(&loop);
__ mov_b(scratch, Operand(src, 0));
__ mov_b(Operand(dest, 0), scratch);
- __ add(src, Immediate(1));
- __ add(dest, Immediate(1));
- __ sub(count, Immediate(1));
+ __ inc(src);
+ __ inc(dest);
+ __ dec(count);
__ j(not_zero, &loop);
__ bind(&done);
@@ -3137,23 +3110,21 @@
// eax: result string
// ecx: result string length
- __ mov(edx, esi); // esi used by following code.
// Locate first character of result.
__ mov(edi, eax);
__ add(edi, Immediate(SeqOneByteString::kHeaderSize - kHeapObjectTag));
// Load string argument and locate character of sub string start.
- __ pop(esi);
+ __ pop(edx);
__ pop(ebx);
__ SmiUntag(ebx);
- __ lea(esi, FieldOperand(esi, ebx, times_1,
SeqOneByteString::kHeaderSize));
+ __ lea(edx, FieldOperand(edx, ebx, times_1,
SeqOneByteString::kHeaderSize));
// eax: result string
// ecx: result length
- // edx: original value of esi
// edi: first character of result
- // esi: character of sub string start
- StringHelper::GenerateCopyCharactersREP(masm, edi, esi, ecx, ebx, true);
- __ mov(esi, edx); // Restore esi.
+ // edx: character of sub string start
+ StringHelper::GenerateCopyCharacters(
+ masm, edi, edx, ecx, ebx, String::ONE_BYTE_ENCODING);
__ IncrementCounter(counters->sub_string_native(), 1);
__ ret(3 * kPointerSize);
@@ -3163,27 +3134,25 @@
// eax: result string
// ecx: result string length
- __ mov(edx, esi); // esi used by following code.
// Locate first character of result.
__ mov(edi, eax);
__ add(edi,
Immediate(SeqTwoByteString::kHeaderSize - kHeapObjectTag));
// Load string argument and locate character of sub string start.
- __ pop(esi);
+ __ pop(edx);
__ pop(ebx);
// As from is a smi it is 2 times the value which matches the size of a
two
// byte character.
STATIC_ASSERT(kSmiTag == 0);
STATIC_ASSERT(kSmiTagSize + kSmiShiftSize == 1);
- __ lea(esi, FieldOperand(esi, ebx, times_1,
SeqTwoByteString::kHeaderSize));
+ __ lea(edx, FieldOperand(edx, ebx, times_1,
SeqTwoByteString::kHeaderSize));
// eax: result string
// ecx: result length
- // edx: original value of esi
// edi: first character of result
- // esi: character of sub string start
- StringHelper::GenerateCopyCharactersREP(masm, edi, esi, ecx, ebx, false);
- __ mov(esi, edx); // Restore esi.
+ // edx: character of sub string start
+ StringHelper::GenerateCopyCharacters(
+ masm, edi, edx, ecx, ebx, String::TWO_BYTE_ENCODING);
__ IncrementCounter(counters->sub_string_native(), 1);
__ ret(3 * kPointerSize);
Index: src/x87/code-stubs-x87.h
===================================================================
--- src/x87/code-stubs-x87.h (revision 21759)
+++ src/x87/code-stubs-x87.h (working copy)
@@ -38,12 +38,12 @@
// Generate code for copying characters using the rep movs instruction.
// Copies ecx characters from esi to edi. Copying of overlapping regions
is
// not supported.
- static void GenerateCopyCharactersREP(MacroAssembler* masm,
- Register dest, // Must be edi.
- Register src, // Must be esi.
- Register count, // Must be ecx.
- Register scratch, // Neither of
above.
- bool ascii);
+ static void GenerateCopyCharacters(MacroAssembler* masm,
+ Register dest,
+ Register src,
+ Register count,
+ Register scratch,
+ String::Encoding encoding);
// Generate string hash.
static void GenerateHashInit(MacroAssembler* masm,
--
--
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