Revision: 21773
Author: plin...@gmail.com
Date: Wed Jun 11 14:44:13 2014 UTC
Log: MIPS: Simplify string copy in SubStringStub.
Port r21756 (3d58e58)
Original commit message:
The optimizations are unnecessary since the maximum
string length they operate on is currently 12.
BUG=352155
LOG=N
R=plin...@gmail.com
Review URL: https://codereview.chromium.org/326413002
Patch from Balazs Kilvady <kilva...@homejinni.com>.
http://code.google.com/p/v8/source/detail?r=21773
Modified:
/branches/bleeding_edge/src/mips/code-stubs-mips.cc
/branches/bleeding_edge/src/mips/code-stubs-mips.h
=======================================
--- /branches/bleeding_edge/src/mips/code-stubs-mips.cc Tue Jun 3 08:12:43
2014 UTC
+++ /branches/bleeding_edge/src/mips/code-stubs-mips.cc Wed Jun 11 14:44:13
2014 UTC
@@ -3498,119 +3498,42 @@
};
-void StringHelper::GenerateCopyCharactersLong(MacroAssembler* masm,
- Register dest,
- Register src,
- Register count,
- Register scratch1,
- Register scratch2,
- Register scratch3,
- Register scratch4,
- Register scratch5,
- 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.
- __ And(scratch4, dest, Operand(kPointerAlignmentMask));
+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.
+ __ And(scratch, dest, Operand(kPointerAlignmentMask));
__ Check(eq,
kDestinationOfCopyNotAligned,
- scratch4,
+ scratch,
Operand(zero_reg));
}
- 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) {
- __ addu(count, count, count);
+ if (encoding == String::TWO_BYTE_ENCODING) {
+ __ Addu(count, count, count);
}
- __ Branch(&done, eq, count, Operand(zero_reg));
- Label byte_loop;
- // Must copy at least eight bytes, otherwise just do it one byte at a
time.
- __ Subu(scratch1, count, Operand(8));
- __ Addu(count, dest, Operand(count));
- Register limit = count; // Read until src equals this.
- __ Branch(&byte_loop, lt, scratch1, Operand(zero_reg));
+ Register limit = count; // Read until dest equals this.
+ __ Addu(limit, dest, Operand(count));
- if (!dest_always_aligned) {
- // Align dest by byte copying. Copies between zero and three bytes.
- __ And(scratch4, dest, Operand(kReadAlignmentMask));
- Label dest_aligned;
- __ Branch(&dest_aligned, eq, scratch4, Operand(zero_reg));
- Label aligned_loop;
- __ bind(&aligned_loop);
- __ lbu(scratch1, MemOperand(src));
- __ addiu(src, src, 1);
- __ sb(scratch1, MemOperand(dest));
- __ addiu(dest, dest, 1);
- __ addiu(scratch4, scratch4, 1);
- __ Branch(&aligned_loop, le, scratch4, Operand(kReadAlignmentMask));
- __ bind(&dest_aligned);
- }
-
- Label simple_loop;
-
- __ And(scratch4, src, Operand(kReadAlignmentMask));
- __ Branch(&simple_loop, eq, scratch4, Operand(zero_reg));
-
- // Loop for src/dst that are not aligned the same way.
- // This loop uses lwl and lwr instructions. These instructions
- // depend on the endianness, and the implementation assumes
little-endian.
- {
- Label loop;
- __ bind(&loop);
- if (kArchEndian == kBig) {
- __ lwl(scratch1, MemOperand(src));
- __ Addu(src, src, Operand(kReadAlignment));
- __ lwr(scratch1, MemOperand(src, -1));
- } else {
- __ lwr(scratch1, MemOperand(src));
- __ Addu(src, src, Operand(kReadAlignment));
- __ lwl(scratch1, MemOperand(src, -1));
- }
- __ sw(scratch1, MemOperand(dest));
- __ Addu(dest, dest, Operand(kReadAlignment));
- __ Subu(scratch2, limit, dest);
- __ Branch(&loop, ge, scratch2, Operand(kReadAlignment));
- }
-
- __ Branch(&byte_loop);
-
- // Simple loop.
- // Copy words from src to dest, until less than four bytes left.
- // Both src and dest are word aligned.
- __ bind(&simple_loop);
- {
- Label loop;
- __ bind(&loop);
- __ lw(scratch1, MemOperand(src));
- __ Addu(src, src, Operand(kReadAlignment));
- __ sw(scratch1, MemOperand(dest));
- __ Addu(dest, dest, Operand(kReadAlignment));
- __ Subu(scratch2, limit, dest);
- __ Branch(&loop, ge, scratch2, Operand(kReadAlignment));
- }
-
+ Label loop_entry, loop;
// Copy bytes from src to dest until dest hits limit.
- __ bind(&byte_loop);
- // Test if dest has already reached the limit.
- __ Branch(&done, ge, dest, Operand(limit));
- __ lbu(scratch1, MemOperand(src));
- __ addiu(src, src, 1);
- __ sb(scratch1, MemOperand(dest));
- __ addiu(dest, dest, 1);
- __ Branch(&byte_loop);
+ __ Branch(&loop_entry);
+ __ bind(&loop);
+ __ lbu(scratch, MemOperand(src));
+ __ Addu(src, src, Operand(1));
+ __ sb(scratch, MemOperand(dest));
+ __ Addu(dest, dest, Operand(1));
+ __ bind(&loop_entry);
+ __ Branch(&loop, lt, dest, Operand(limit));
__ bind(&done);
}
@@ -3844,8 +3767,8 @@
// a2: result string length
// t1: first character of substring to copy
STATIC_ASSERT((SeqOneByteString::kHeaderSize & kObjectAlignmentMask) ==
0);
- StringHelper::GenerateCopyCharactersLong(
- masm, a1, t1, a2, a3, t0, t2, t3, t4, COPY_ASCII |
DEST_ALWAYS_ALIGNED);
+ StringHelper::GenerateCopyCharacters(
+ masm, a1, t1, a2, a3, String::ONE_BYTE_ENCODING);
__ jmp(&return_v0);
// Allocate and copy the resulting two-byte string.
@@ -3864,8 +3787,8 @@
// a2: result length.
// t1: first character of substring to copy.
STATIC_ASSERT((SeqTwoByteString::kHeaderSize & kObjectAlignmentMask) ==
0);
- StringHelper::GenerateCopyCharactersLong(
- masm, a1, t1, a2, a3, t0, t2, t3, t4, DEST_ALWAYS_ALIGNED);
+ StringHelper::GenerateCopyCharacters(
+ masm, a1, t1, a2, a3, String::TWO_BYTE_ENCODING);
__ bind(&return_v0);
Counters* counters = isolate()->counters();
=======================================
--- /branches/bleeding_edge/src/mips/code-stubs-mips.h Tue Jun 3 08:12:43
2014 UTC
+++ /branches/bleeding_edge/src/mips/code-stubs-mips.h Wed Jun 11 14:44:13
2014 UTC
@@ -39,16 +39,12 @@
// 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,
- Register scratch5,
- int flags);
+ static void GenerateCopyCharacters(MacroAssembler* masm,
+ Register dest,
+ Register src,
+ Register count,
+ Register scratch,
+ String::Encoding encoding);
// Generate string hash.
--
--
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