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| author | Keith Randall <khr@golang.org> | 2016-03-29 21:25:33 -0700 |
|---|---|---|
| committer | Keith Randall <khr@golang.org> | 2016-03-31 02:54:10 +0000 |
| commit | 4b209dbf0bf3e5fd4cffda1e11f11bf45ddf212d (patch) | |
| tree | a7af96647c02144a3e82b576eb72d1704bf2f6ff /src/runtime/memmove_386.s | |
| parent | 1a9373bc570cf408cecdfab5d531e8041f354a54 (diff) | |
| download | go-4b209dbf0bf3e5fd4cffda1e11f11bf45ddf212d.tar.gz go-4b209dbf0bf3e5fd4cffda1e11f11bf45ddf212d.zip | |
runtime: don't use REP;MOVSB if CPUID doesn't say it is fast
Only use REP;MOVSB if:
1) The CPUID flag says it is fast, and
2) The pointers are unaligned
Otherwise, use REP;MOVSQ.
Update #14630
Change-Id: I946b28b87880c08e5eed1ce2945016466c89db66
Reviewed-on: https://go-review.googlesource.com/21300
Reviewed-by: Nigel Tao <nigeltao@golang.org>
Diffstat (limited to 'src/runtime/memmove_386.s')
| -rw-r--r-- | src/runtime/memmove_386.s | 19 |
1 files changed, 12 insertions, 7 deletions
diff --git a/src/runtime/memmove_386.s b/src/runtime/memmove_386.s index d4baf2280a..52b35a6ac7 100644 --- a/src/runtime/memmove_386.s +++ b/src/runtime/memmove_386.s @@ -70,24 +70,29 @@ nosse2: * forward copy loop */ forward: + // If REP MOVSB isn't fast, don't use it + TESTL $(1<<9), runtime·cpuid_ebx7(SB) // erms, aka enhanced REP MOVSB/STOSB + JEQ fwdBy4 + // Check alignment MOVL SI, AX ORL DI, AX TESTL $3, AX - JNE unaligned_fwd + JEQ fwdBy4 + + // Do 1 byte at a time + MOVL BX, CX + REP; MOVSB + RET +fwdBy4: + // Do 4 bytes at a time MOVL BX, CX SHRL $2, CX ANDL $3, BX - REP; MOVSL JMP tail -unaligned_fwd: - MOVL BX, CX - REP; MOVSB - RET - /* * check overlap */ |