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| author | erifan01 <eric.fang@arm.com> | 2019-01-03 09:25:06 +0000 |
|---|---|---|
| committer | Cherry Zhang <cherryyz@google.com> | 2019-03-07 14:24:56 +0000 |
| commit | 4e2b0dda8cbab104635d59ef5a68e4342250094b (patch) | |
| tree | 133c8b50fbba6bf4e74e5c843cec9360ee9644b7 /test/codegen | |
| parent | fee84cc90542884edda60d3eec2cd47f72d67118 (diff) | |
| download | go-4e2b0dda8cbab104635d59ef5a68e4342250094b.tar.xz | |
cmd/compile: eliminate unnecessary type conversions in TrailingZeros(16|8) for arm64
This CL eliminates unnecessary type conversion operations: OpZeroExt16to64 and OpZeroExt8to64.
If the input argrument is a nonzero value, then ORconst operation can also be eliminated.
Benchmarks:
name old time/op new time/op delta
TrailingZeros-8 2.75ns ± 0% 2.75ns ± 0% ~ (all equal)
TrailingZeros8-8 3.49ns ± 1% 2.93ns ± 0% -16.00% (p=0.000 n=10+10)
TrailingZeros16-8 3.49ns ± 1% 2.93ns ± 0% -16.05% (p=0.000 n=9+10)
TrailingZeros32-8 2.67ns ± 1% 2.68ns ± 1% ~ (p=0.468 n=10+10)
TrailingZeros64-8 2.67ns ± 1% 2.65ns ± 0% -0.62% (p=0.022 n=10+9)
code:
func f16(x uint) { z = bits.TrailingZeros16(uint16(x)) }
Before:
"".f16 STEXT size=48 args=0x8 locals=0x0 leaf
0x0000 00000 (test.go:7) TEXT "".f16(SB), LEAF|NOFRAME|ABIInternal, $0-8
0x0000 00000 (test.go:7) FUNCDATA ZR, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (test.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (test.go:7) FUNCDATA $3, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (test.go:7) PCDATA $2, ZR
0x0000 00000 (test.go:7) PCDATA ZR, ZR
0x0000 00000 (test.go:7) MOVD "".x(FP), R0
0x0004 00004 (test.go:7) MOVHU R0, R0
0x0008 00008 (test.go:7) ORR $65536, R0, R0
0x000c 00012 (test.go:7) RBIT R0, R0
0x0010 00016 (test.go:7) CLZ R0, R0
0x0014 00020 (test.go:7) MOVD R0, "".z(SB)
0x0020 00032 (test.go:7) RET (R30)
This line of code is unnecessary:
0x0004 00004 (test.go:7) MOVHU R0, R0
After:
"".f16 STEXT size=32 args=0x8 locals=0x0 leaf
0x0000 00000 (test.go:7) TEXT "".f16(SB), LEAF|NOFRAME|ABIInternal, $0-8
0x0000 00000 (test.go:7) FUNCDATA ZR, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (test.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (test.go:7) FUNCDATA $3, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (test.go:7) PCDATA $2, ZR
0x0000 00000 (test.go:7) PCDATA ZR, ZR
0x0000 00000 (test.go:7) MOVD "".x(FP), R0
0x0004 00004 (test.go:7) ORR $65536, R0, R0
0x0008 00008 (test.go:7) RBITW R0, R0
0x000c 00012 (test.go:7) CLZW R0, R0
0x0010 00016 (test.go:7) MOVD R0, "".z(SB)
0x001c 00028 (test.go:7) RET (R30)
The situation of TrailingZeros8 is similar to TrailingZeros16.
Change-Id: I473bdca06be8460a0be87abbae6fe640017e4c9d
Reviewed-on: https://go-review.googlesource.com/c/go/+/156999
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Diffstat (limited to 'test/codegen')
| -rw-r--r-- | test/codegen/mathbits.go | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/test/codegen/mathbits.go b/test/codegen/mathbits.go index 09939bb6be..c77b66c3f7 100644 --- a/test/codegen/mathbits.go +++ b/test/codegen/mathbits.go @@ -242,6 +242,7 @@ func RotateLeftVariable32(n uint32, m int) uint32 { func TrailingZeros(n uint) int { // amd64:"BSFQ","MOVL\t\\$64","CMOVQEQ" + // arm64:"RBIT","CLZ" // s390x:"FLOGR" // ppc64:"ANDN","POPCNTD" // ppc64le:"ANDN","POPCNTD" @@ -250,6 +251,7 @@ func TrailingZeros(n uint) int { func TrailingZeros64(n uint64) int { // amd64:"BSFQ","MOVL\t\\$64","CMOVQEQ" + // arm64:"RBIT","CLZ" // s390x:"FLOGR" // ppc64:"ANDN","POPCNTD" // ppc64le:"ANDN","POPCNTD" @@ -258,6 +260,7 @@ func TrailingZeros64(n uint64) int { func TrailingZeros32(n uint32) int { // amd64:"BTSQ\\t\\$32","BSFQ" + // arm64:"RBITW","CLZW" // s390x:"FLOGR","MOVWZ" // ppc64:"ANDN","POPCNTW" // ppc64le:"ANDN","POPCNTW" @@ -266,6 +269,7 @@ func TrailingZeros32(n uint32) int { func TrailingZeros16(n uint16) int { // amd64:"BSFL","BTSL\\t\\$16" + // arm64:"ORR\t\\$65536","RBITW","CLZW",-"MOVHU\tR",-"RBIT\t",-"CLZ\t" // s390x:"FLOGR","OR\t\\$65536" // ppc64:"POPCNTD","OR\\t\\$65536" // ppc64le:"POPCNTD","OR\\t\\$65536" @@ -274,6 +278,7 @@ func TrailingZeros16(n uint16) int { func TrailingZeros8(n uint8) int { // amd64:"BSFL","BTSL\\t\\$8" + // arm64:"ORR\t\\$256","RBITW","CLZW",-"MOVBU\tR",-"RBIT\t",-"CLZ\t" // s390x:"FLOGR","OR\t\\$256" return bits.TrailingZeros8(n) } @@ -314,6 +319,7 @@ func IterateBits16(n uint16) int { i := 0 for n != 0 { // amd64:"BSFL",-"BTSL" + // arm64:"RBITW","CLZW",-"ORR" i += bits.TrailingZeros16(n) n &= n - 1 } @@ -324,6 +330,7 @@ func IterateBits8(n uint8) int { i := 0 for n != 0 { // amd64:"BSFL",-"BTSL" + // arm64:"RBITW","CLZW",-"ORR" i += bits.TrailingZeros8(n) n &= n - 1 } |