go/src/math/sqrt_amd64.s

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

#include "textflag.h"

// func Sqrt(x float64) float64
TEXT ·Sqrt(SB), NOSPLIT, $0
	XORPS  X0, X0 // break dependency
	SQRTSD x+0(FP), X0
	MOVSD  X0, ret+8(FP)
	RET
all: make copyright headers consistent with one space after period This is a subset of https://golang.org/cl/20022 with only the copyright header lines, so the next CL will be smaller and more reviewable. Go policy has been single space after periods in comments for some time. The copyright header template at: https://golang.org/doc/contribute.html#copyright also uses a single space. Make them all consistent. Change-Id: Icc26c6b8495c3820da6b171ca96a74701b4a01b0 Reviewed-on: https://go-review.googlesource.com/20111 Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> 2016-03-01 15:57:46 -07:00			`// Copyright 2009 The Go Authors. All rights reserved.`
install assembly math.Sqrt on amd64 R=r DELTA=33 (32 added, 0 deleted, 1 changed) OCL=34983 CL=34986 2009-09-24 15:27:52 -06:00			`// Use of this source code is governed by a BSD-style`
			`// license that can be found in the LICENSE file.`

all: copy cmd/ld/textflag.h into pkg/GOOS_GOARCH The file is used by assembly code to define symbols like NOSPLIT. Having it hidden inside the cmd directory makes it hard to access outside the standard repository. Solution: As with a couple of other files used by cgo, copy the file into the pkg directory and add a -I argument to the assembler to access it. Thus one can write just #include "textflag.h" in .s files. The names in runtime are not updated because in the boot sequence the file has not been copied yet when runtime is built. All other .s files in the repository are updated. Changes to doc/asm.html, src/cmd/dist/build.c, and src/cmd/go/build.go are hand-made. The rest are just the renaming done by a global substitution. (Yay sam). LGTM=rsc R=rsc CC=golang-codereviews https://golang.org/cl/128050043 2014-08-12 18:04:45 -06:00			`#include "textflag.h"`
math: convert textflags from numbers to symbols R=golang-dev, bradfitz CC=golang-dev https://golang.org/cl/12773044 2013-08-12 11:25:18 -06:00
install assembly math.Sqrt on amd64 R=r DELTA=33 (32 added, 0 deleted, 1 changed) OCL=34983 CL=34986 2009-09-24 15:27:52 -06:00			`// func Sqrt(x float64) float64`
math: fix sqrt regression on AMD64 1.7 introduced a significant regression compared to 1.6: SqrtIndirect-4 2.32ns ± 0% 7.86ns ± 0% +238.79% (p=0.000 n=20+18) This is caused by sqrtsd preserving upper part of destination register. Which introduces dependency on previous value of X0. In 1.6 benchmark loop didn't use X0 immediately after call: callq %rbx movsd 0x8(%rsp),%xmm2 movsd 0x20(%rsp),%xmm1 addsd %xmm2,%xmm1 mov 0x18(%rsp),%rax inc %rax jmp loop In 1.7 however xmm0 is used just after call: callq %rbx mov 0x10(%rsp),%rcx lea 0x1(%rcx),%rax movsd 0x8(%rsp),%xmm0 movsd 0x18(%rsp),%xmm1 I've verified that this is caused by dependency, by inserting XORPS X0,X0 in the beginning of math.Sqrt, which puts performance back on 1.6 level. Splitting SQRTSD mem,reg into: MOVSD mem,reg SQRTSD reg,reg Removes dependency, because MOVSD (load version) doesn't need to preserve upper part of a register. And reg,reg operation is solved by renamer in CPU. As a result of this change regression is gone: SqrtIndirect-4 7.86ns ± 0% 2.33ns ± 0% -70.36% (p=0.000 n=18+17) This also removes old Sqrt benchmarks, in favor of benchmarks measuring latency. Only SqrtIndirect is kept, to show impact of this patch. Change-Id: Ic7eebe8866445adff5bc38192fa8d64c9a6b8872 Reviewed-on: https://go-review.googlesource.com/28392 Run-TryBot: Ilya Tocar <ilya.tocar@intel.com> Reviewed-by: Keith Randall <khr@golang.org> 2016-09-01 12:04:08 -06:00			`TEXT ·Sqrt(SB), NOSPLIT, $0`
math: make sqrt smaller on AMD64 This makes function fit in 16 bytes, saving 16 bytes. Change-Id: Iac5d2add42f6dae985b2a5cbe19ad4bd4bcc92ec Reviewed-on: https://go-review.googlesource.com/29151 Run-TryBot: Ilya Tocar <ilya.tocar@intel.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org> 2016-09-14 06:23:41 -06:00			`XORPS X0, X0 // break dependency`
			`SQRTSD x+0(FP), X0`
			`MOVSD X0, ret+8(FP)`
install assembly math.Sqrt on amd64 R=r DELTA=33 (32 added, 0 deleted, 1 changed) OCL=34983 CL=34986 2009-09-24 15:27:52 -06:00			`RET`