Revision: 21756
Author: yang...@chromium.org
Date: Wed Jun 11 06:59:25 2014 UTC
Log: Simplify string copy in SubStringStub.
The optimizations are unnecessary since the maximum
string length they operate on is currently 12.
R=bmeu...@chromium.org
BUG=352155
LOG=N
Review URL: https://codereview.chromium.org/326943002
http://code.google.com/p/v8/source/detail?r=21756
Modified:
/branches/bleeding_edge/src/arm/code-stubs-arm.cc
/branches/bleeding_edge/src/arm/code-stubs-arm.h
/branches/bleeding_edge/src/ia32/code-stubs-ia32.cc
/branches/bleeding_edge/src/ia32/code-stubs-ia32.h
/branches/bleeding_edge/src/x64/code-stubs-x64.cc
/branches/bleeding_edge/src/x64/code-stubs-x64.h
=======================================
--- /branches/bleeding_edge/src/arm/code-stubs-arm.cc Tue Jun 3 08:12:43
2014 UTC
+++ /branches/bleeding_edge/src/arm/code-stubs-arm.cc Wed Jun 11 06:59:25
2014 UTC
@@ -3322,142 +3322,37 @@
};
-void StringHelper::GenerateCopyCharactersLong(MacroAssembler* masm,
- Register dest,
- Register src,
- Register count,
- Register scratch1,
- Register scratch2,
- Register scratch3,
- Register scratch4,
- int flags) {
- bool ascii = (flags & COPY_ASCII) != 0;
- bool dest_always_aligned = (flags & DEST_ALWAYS_ALIGNED) != 0;
-
- if (dest_always_aligned && FLAG_debug_code) {
- // Check that destination is actually word aligned if the flag says
- // that it is.
+void StringHelper::GenerateCopyCharacters(MacroAssembler* masm,
+ Register dest,
+ Register src,
+ Register count,
+ Register scratch,
+ String::Encoding encoding) {
+ if (FLAG_debug_code) {
+ // Check that destination is word aligned.
__ tst(dest, Operand(kPointerAlignmentMask));
__ Check(eq, kDestinationOfCopyNotAligned);
}
- const int kReadAlignment = 4;
- const int kReadAlignmentMask = kReadAlignment - 1;
- // Ensure that reading an entire aligned word containing the last
character
- // of a string will not read outside the allocated area (because we pad
up
- // to kObjectAlignment).
- STATIC_ASSERT(kObjectAlignment >= kReadAlignment);
// Assumes word reads and writes are little endian.
// Nothing to do for zero characters.
Label done;
- if (!ascii) {
+ if (encoding == String::TWO_BYTE_ENCODING) {
__ add(count, count, Operand(count), SetCC);
- } else {
- __ cmp(count, Operand::Zero());
}
- __ b(eq, &done);
- // Assume that you cannot read (or write) unaligned.
- Label byte_loop;
- // Must copy at least eight bytes, otherwise just do it one byte at a
time.
- __ cmp(count, Operand(8));
- __ add(count, dest, Operand(count));
- Register limit = count; // Read until src equals this.
- __ b(lt, &byte_loop);
+ Register limit = count; // Read until dest equals this.
+ __ add(limit, dest, Operand(count));
- if (!dest_always_aligned) {
- // Align dest by byte copying. Copies between zero and three bytes.
- __ and_(scratch4, dest, Operand(kReadAlignmentMask), SetCC);
- Label dest_aligned;
- __ b(eq, &dest_aligned);
- __ cmp(scratch4, Operand(2));
- __ ldrb(scratch1, MemOperand(src, 1, PostIndex));
- __ ldrb(scratch2, MemOperand(src, 1, PostIndex), le);
- __ ldrb(scratch3, MemOperand(src, 1, PostIndex), lt);
- __ strb(scratch1, MemOperand(dest, 1, PostIndex));
- __ strb(scratch2, MemOperand(dest, 1, PostIndex), le);
- __ strb(scratch3, MemOperand(dest, 1, PostIndex), lt);
- __ bind(&dest_aligned);
- }
-
- Label simple_loop;
-
- __ sub(scratch4, dest, Operand(src));
- __ and_(scratch4, scratch4, Operand(0x03), SetCC);
- __ b(eq, &simple_loop);
- // Shift register is number of bits in a source word that
- // must be combined with bits in the next source word in order
- // to create a destination word.
-
- // Complex loop for src/dst that are not aligned the same way.
- {
- Label loop;
- __ mov(scratch4, Operand(scratch4, LSL, 3));
- Register left_shift = scratch4;
- __ and_(src, src, Operand(~3)); // Round down to load previous word.
- __ ldr(scratch1, MemOperand(src, 4, PostIndex));
- // Store the "shift" most significant bits of scratch in the least
- // signficant bits (i.e., shift down by (32-shift)).
- __ rsb(scratch2, left_shift, Operand(32));
- Register right_shift = scratch2;
- __ mov(scratch1, Operand(scratch1, LSR, right_shift));
-
- __ bind(&loop);
- __ ldr(scratch3, MemOperand(src, 4, PostIndex));
- __ orr(scratch1, scratch1, Operand(scratch3, LSL, left_shift));
- __ str(scratch1, MemOperand(dest, 4, PostIndex));
- __ mov(scratch1, Operand(scratch3, LSR, right_shift));
- // Loop if four or more bytes left to copy.
- __ sub(scratch3, limit, Operand(dest));
- __ sub(scratch3, scratch3, Operand(4), SetCC);
- __ b(ge, &loop);
- }
- // There is now between zero and three bytes left to copy (negative that
- // number is in scratch3), and between one and three bytes already read
into
- // scratch1 (eight times that number in scratch4). We may have read past
- // the end of the string, but because objects are aligned, we have not
read
- // past the end of the object.
- // Find the minimum of remaining characters to move and preloaded
characters
- // and write those as bytes.
- __ add(scratch3, scratch3, Operand(4), SetCC);
- __ b(eq, &done);
- __ cmp(scratch4, Operand(scratch3, LSL, 3), ne);
- // Move minimum of bytes read and bytes left to copy to scratch4.
- __ mov(scratch3, Operand(scratch4, LSR, 3), LeaveCC, lt);
- // Between one and three (value in scratch3) characters already read into
- // scratch ready to write.
- __ cmp(scratch3, Operand(2));
- __ strb(scratch1, MemOperand(dest, 1, PostIndex));
- __ mov(scratch1, Operand(scratch1, LSR, 8), LeaveCC, ge);
- __ strb(scratch1, MemOperand(dest, 1, PostIndex), ge);
- __ mov(scratch1, Operand(scratch1, LSR, 8), LeaveCC, gt);
- __ strb(scratch1, MemOperand(dest, 1, PostIndex), gt);
- // Copy any remaining bytes.
- __ b(&byte_loop);
-
- // Simple loop.
- // Copy words from src to dst, until less than four bytes left.
- // Both src and dest are word aligned.
- __ bind(&simple_loop);
- {
- Label loop;
- __ bind(&loop);
- __ ldr(scratch1, MemOperand(src, 4, PostIndex));
- __ sub(scratch3, limit, Operand(dest));
- __ str(scratch1, MemOperand(dest, 4, PostIndex));
- // Compare to 8, not 4, because we do the substraction before
increasing
- // dest.
- __ cmp(scratch3, Operand(8));
- __ b(ge, &loop);
- }
-
- // Copy bytes from src to dst until dst hits limit.
- __ bind(&byte_loop);
+ Label loop_entry, loop;
+ // Copy bytes from src to dest until dest hits limit.
+ __ b(&loop_entry);
+ __ bind(&loop);
+ __ ldrb(scratch, MemOperand(src, 1, PostIndex), lt);
+ __ strb(scratch, MemOperand(dest, 1, PostIndex));
+ __ bind(&loop_entry);
__ cmp(dest, Operand(limit));
- __ ldrb(scratch1, MemOperand(src, 1, PostIndex), lt);
- __ b(ge, &done);
- __ strb(scratch1, MemOperand(dest, 1, PostIndex));
- __ b(&byte_loop);
+ __ b(lt, &loop);
__ bind(&done);
}
@@ -3683,8 +3578,8 @@
// r2: result string length
// r5: first character of substring to copy
STATIC_ASSERT((SeqOneByteString::kHeaderSize & kObjectAlignmentMask) ==
0);
- StringHelper::GenerateCopyCharactersLong(masm, r1, r5, r2, r3, r4, r6,
r9,
- COPY_ASCII |
DEST_ALWAYS_ALIGNED);
+ StringHelper::GenerateCopyCharacters(
+ masm, r1, r5, r2, r3, String::ONE_BYTE_ENCODING);
__ jmp(&return_r0);
// Allocate and copy the resulting two-byte string.
@@ -3702,8 +3597,8 @@
// r2: result length.
// r5: first character of substring to copy.
STATIC_ASSERT((SeqTwoByteString::kHeaderSize & kObjectAlignmentMask) ==
0);
- StringHelper::GenerateCopyCharactersLong(
- masm, r1, r5, r2, r3, r4, r6, r9, DEST_ALWAYS_ALIGNED);
+ StringHelper::GenerateCopyCharacters(
+ masm, r1, r5, r2, r3, String::TWO_BYTE_ENCODING);
__ bind(&return_r0);
Counters* counters = isolate()->counters();
=======================================
--- /branches/bleeding_edge/src/arm/code-stubs-arm.h Tue Jun 3 08:12:43
2014 UTC
+++ /branches/bleeding_edge/src/arm/code-stubs-arm.h Wed Jun 11 06:59:25
2014 UTC
@@ -38,15 +38,12 @@
// is allowed to spend extra time setting up conditions to make copying
// faster. Copying of overlapping regions is not supported.
// Dest register ends at the position after the last character written.
- static void GenerateCopyCharactersLong(MacroAssembler* masm,
- Register dest,
- Register src,
- Register count,
- Register scratch1,
- Register scratch2,
- Register scratch3,
- Register scratch4,
- int flags);
+ static void GenerateCopyCharacters(MacroAssembler* masm,
+ Register dest,
+ Register src,
+ Register count,
+ Register scratch,
+ String::Encoding encoding);
// Generate string hash.
=======================================
--- /branches/bleeding_edge/src/ia32/code-stubs-ia32.cc Tue Jun 3 08:12:43
2014 UTC
+++ /branches/bleeding_edge/src/ia32/code-stubs-ia32.cc Wed Jun 11 06:59:25
2014 UTC
@@ -3180,18 +3180,12 @@
}
-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));
@@ -3202,38 +3196,17 @@
__ 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);
@@ -3462,23 +3435,21 @@
// 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);
@@ -3488,27 +3459,25 @@
// 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);
=======================================
--- /branches/bleeding_edge/src/ia32/code-stubs-ia32.h Tue Jun 3 08:12:43
2014 UTC
+++ /branches/bleeding_edge/src/ia32/code-stubs-ia32.h Wed Jun 11 06:59:25
2014 UTC
@@ -40,12 +40,12 @@
// 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,
=======================================
--- /branches/bleeding_edge/src/x64/code-stubs-x64.cc Tue Jun 3 08:12:43
2014 UTC
+++ /branches/bleeding_edge/src/x64/code-stubs-x64.cc Wed Jun 11 06:59:25
2014 UTC
@@ -3134,49 +3134,21 @@
}
-void StringHelper::GenerateCopyCharactersREP(MacroAssembler* masm,
- Register dest,
- Register src,
- Register count,
- bool ascii) {
- // Copy characters using rep movs of doublewords. Align destination on 4
byte
- // boundary before starting rep movs. Copy remaining characters after
running
- // rep movs.
- // Count is positive int32, dest and src are character pointers.
- ASSERT(dest.is(rdi)); // rep movs destination
- ASSERT(src.is(rsi)); // rep movs source
- ASSERT(count.is(rcx)); // rep movs count
-
+void StringHelper::GenerateCopyCharacters(MacroAssembler* masm,
+ Register dest,
+ Register src,
+ Register count,
+ String::Encoding encoding) {
// Nothing to do for zero characters.
Label done;
__ testl(count, count);
__ j(zero, &done, Label::kNear);
// Make count the number of bytes to copy.
- if (!ascii) {
+ if (encoding == String::TWO_BYTE_ENCODING) {
STATIC_ASSERT(2 == sizeof(uc16));
__ addl(count, count);
}
-
- // Don't enter the rep movs if there are less than 4 bytes to copy.
- Label last_bytes;
- __ testl(count, Immediate(~(kPointerSize - 1)));
- __ j(zero, &last_bytes, Label::kNear);
-
- // Copy from edi to esi using rep movs instruction.
- __ movl(kScratchRegister, count);
- // Number of doublewords to copy.
- __ shrl(count, Immediate(kPointerSizeLog2));
- __ repmovsp();
-
- // Find number of bytes left.
- __ movl(count, kScratchRegister);
- __ andp(count, Immediate(kPointerSize - 1));
-
- // Check if there are more bytes to copy.
- __ bind(&last_bytes);
- __ testl(count, count);
- __ j(zero, &done, Label::kNear);
// Copy remaining characters.
Label loop;
@@ -3415,10 +3387,9 @@
// rax: result string
// rcx: result string length
- __ movp(r14, rsi); // esi used by following code.
{ // Locate character of sub string start.
SmiIndex smi_as_index = masm->SmiToIndex(rdx, rdx, times_1);
- __ leap(rsi, Operand(rdi, smi_as_index.reg, smi_as_index.scale,
+ __ leap(r14, Operand(rdi, smi_as_index.reg, smi_as_index.scale,
SeqOneByteString::kHeaderSize - kHeapObjectTag));
}
// Locate first character of result.
@@ -3426,11 +3397,10 @@
// rax: result string
// rcx: result length
- // rdi: first character of result
+ // r14: first character of result
// rsi: character of sub string start
- // r14: original value of rsi
- StringHelper::GenerateCopyCharactersREP(masm, rdi, rsi, rcx, true);
- __ movp(rsi, r14); // Restore rsi.
+ StringHelper::GenerateCopyCharacters(
+ masm, rdi, r14, rcx, String::ONE_BYTE_ENCODING);
__ IncrementCounter(counters->sub_string_native(), 1);
__ ret(SUB_STRING_ARGUMENT_COUNT * kPointerSize);
@@ -3440,10 +3410,9 @@
// rax: result string
// rcx: result string length
- __ movp(r14, rsi); // esi used by following code.
{ // Locate character of sub string start.
SmiIndex smi_as_index = masm->SmiToIndex(rdx, rdx, times_2);
- __ leap(rsi, Operand(rdi, smi_as_index.reg, smi_as_index.scale,
+ __ leap(r14, Operand(rdi, smi_as_index.reg, smi_as_index.scale,
SeqOneByteString::kHeaderSize - kHeapObjectTag));
}
// Locate first character of result.
@@ -3452,10 +3421,9 @@
// rax: result string
// rcx: result length
// rdi: first character of result
- // rsi: character of sub string start
- // r14: original value of rsi
- StringHelper::GenerateCopyCharactersREP(masm, rdi, rsi, rcx, false);
- __ movp(rsi, r14); // Restore esi.
+ // r14: character of sub string start
+ StringHelper::GenerateCopyCharacters(
+ masm, rdi, r14, rcx, String::TWO_BYTE_ENCODING);
__ IncrementCounter(counters->sub_string_native(), 1);
__ ret(SUB_STRING_ARGUMENT_COUNT * kPointerSize);
=======================================
--- /branches/bleeding_edge/src/x64/code-stubs-x64.h Tue Jun 3 08:12:43
2014 UTC
+++ /branches/bleeding_edge/src/x64/code-stubs-x64.h Wed Jun 11 06:59:25
2014 UTC
@@ -36,11 +36,11 @@
// Generate code for copying characters using the rep movs instruction.
// Copies rcx characters from rsi to rdi. Copying of overlapping regions
is
// not supported.
- static void GenerateCopyCharactersREP(MacroAssembler* masm,
- Register dest, // Must be rdi.
- Register src, // Must be rsi.
- Register count, // Must be rcx.
- bool ascii);
+ static void GenerateCopyCharacters(MacroAssembler* masm,
+ Register dest,
+ Register src,
+ Register count,
+ String::Encoding encoding);
// Generate string hash.
--
--
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