Commit 9f7ea616 authored by Michael Munday's avatar Michael Munday

math: optimize Ceil, Floor and Trunc on s390x

Use the FIDBR instruction to round floating-point numbers to integers.

name   old time/op  new time/op  delta
Ceil   14.1ns ± 0%   3.0ns ± 0%  -78.89%  (p=0.000 n=10+10)
Floor  6.42ns ± 0%  3.03ns ± 0%  -52.80%  (p=0.000 n=10+10)
Trunc  6.67ns ± 0%  3.03ns ± 0%  -54.57%   (p=0.000 n=10+9)

Change-Id: I3b416f6d0bccaaa9b547de86356471365862399c
Reviewed-on: https://go-review.googlesource.com/27827Reviewed-by: default avatarBrad Fitzpatrick <bradfitz@golang.org>
parent d2dd0dfd
// Copyright 2016 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 Floor(x float64) float64
TEXT ·Floor(SB),NOSPLIT,$0
FMOVD x+0(FP), F0
FIDBR $7, F0, F0
FMOVD F0, ret+8(FP)
RET
// func Ceil(x float64) float64
TEXT ·Ceil(SB),NOSPLIT,$0
FMOVD x+0(FP), F0
FIDBR $6, F0, F0
FMOVD F0, ret+8(FP)
RET
// func Trunc(x float64) float64
TEXT ·Trunc(SB),NOSPLIT,$0
FMOVD x+0(FP), F0
FIDBR $5, F0, F0
FMOVD F0, ret+8(FP)
RET
......@@ -25,15 +25,6 @@ TEXT ·Expm1(SB),NOSPLIT,$0
TEXT ·Exp(SB),NOSPLIT,$0
BR ·exp(SB)
TEXT ·Floor(SB),NOSPLIT,$0
BR ·floor(SB)
TEXT ·Ceil(SB),NOSPLIT,$0
BR ·ceil(SB)
TEXT ·Trunc(SB),NOSPLIT,$0
BR ·trunc(SB)
TEXT ·Frexp(SB),NOSPLIT,$0
BR ·frexp(SB)
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment