4e2b0dda8c
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> |
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