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| author | Mateusz Guzik <mjg@FreeBSD.org> | 2021-01-31 15:46:18 +0000 |
|---|---|---|
| committer | Mateusz Guzik <mjg@FreeBSD.org> | 2021-01-31 16:07:20 +0000 |
| commit | f1be262ec11c1c35e6485f432415b5b52adb505d (patch) | |
| tree | 24b5d203ad8359ae3d1d181ffe0f2f3df6c31841 /sys/amd64/amd64/support.S | |
| parent | 0db6aef407f30c138982b8cde43189aad098b337 (diff) | |
| download | src-f1be262ec11c1c35e6485f432415b5b52adb505d.tar.gz src-f1be262ec11c1c35e6485f432415b5b52adb505d.zip | |
amd64: move memcmp checks upfront
This is a tradeoff which saves jumps for smaller sizes while making
the 8-16 range slower (roughly in line with the other cases).
Tested with glibc test suite.
For example size 3 (most common with vfs namecache) (ops/s):
before: 407086026
after: 461391995
The regressed range of 8-16 (with 8 as example):
before: 540850489
after: 461671032
Diffstat (limited to 'sys/amd64/amd64/support.S')
| -rw-r--r-- | sys/amd64/amd64/support.S | 52 |
1 files changed, 29 insertions, 23 deletions
diff --git a/sys/amd64/amd64/support.S b/sys/amd64/amd64/support.S index 49baa50ac294..b623fba277db 100644 --- a/sys/amd64/amd64/support.S +++ b/sys/amd64/amd64/support.S @@ -93,9 +93,26 @@ ENTRY(memcmp) cmpq $16,%rdx ja 101632f -100816: cmpb $8,%dl - jl 100408f + jg 100816f + + cmpb $4,%dl + jg 100408f + + cmpb $2,%dl + jge 100204f + + cmpb $1,%dl + jl 100000f + movzbl (%rdi),%eax + movzbl (%rsi),%r8d + subl %r8d,%eax +100000: + POP_FRAME_POINTER + ret + + ALIGN_TEXT +100816: movq (%rdi),%r8 movq (%rsi),%r9 cmpq %r8,%r9 @@ -106,9 +123,8 @@ ENTRY(memcmp) jne 10081608f POP_FRAME_POINTER ret + ALIGN_TEXT 100408: - cmpb $4,%dl - jl 100204f movl (%rdi),%r8d movl (%rsi),%r9d cmpl %r8d,%r9d @@ -119,9 +135,8 @@ ENTRY(memcmp) jne 10040804f POP_FRAME_POINTER ret + ALIGN_TEXT 100204: - cmpb $2,%dl - jl 100001f movzwl (%rdi),%r8d movzwl (%rsi),%r9d cmpl %r8d,%r9d @@ -132,16 +147,7 @@ ENTRY(memcmp) jne 1f POP_FRAME_POINTER ret -100001: - cmpb $1,%dl - jl 100000f - movzbl (%rdi),%eax - movzbl (%rsi),%r8d - subl %r8d,%eax -100000: - POP_FRAME_POINTER - ret -ALIGN_TEXT + ALIGN_TEXT 101632: cmpq $32,%rdx ja 103200f @@ -163,7 +169,7 @@ ALIGN_TEXT jne 10163224f POP_FRAME_POINTER ret -ALIGN_TEXT + ALIGN_TEXT 103200: movq (%rdi),%r8 movq 8(%rdi),%r9 @@ -194,7 +200,7 @@ ALIGN_TEXT * * Before we compute it we narrow down the range (16 -> 8 -> 4 bytes). */ -ALIGN_TEXT + ALIGN_TEXT 10320016: leaq 16(%rdi),%rdi leaq 16(%rsi),%rsi @@ -206,29 +212,29 @@ ALIGN_TEXT leaq 8(%rdi),%rdi leaq 8(%rsi),%rsi jmp 80f -ALIGN_TEXT + ALIGN_TEXT 10081608: 10163224: leaq -8(%rdi,%rdx),%rdi leaq -8(%rsi,%rdx),%rsi jmp 80f -ALIGN_TEXT + ALIGN_TEXT 10163216: leaq -16(%rdi,%rdx),%rdi leaq -16(%rsi,%rdx),%rsi jmp 80f -ALIGN_TEXT + ALIGN_TEXT 10163208: leaq 8(%rdi),%rdi leaq 8(%rsi),%rsi jmp 80f -ALIGN_TEXT + ALIGN_TEXT 10040804: leaq -4(%rdi,%rdx),%rdi leaq -4(%rsi,%rdx),%rsi jmp 1f -ALIGN_TEXT + ALIGN_TEXT 80: movl (%rdi),%r8d movl (%rsi),%r9d |