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go/src/math/floor_s390x.s
Michael Munday 9f7ea61674 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/27827
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
2016-08-26 17:27:13 +00:00

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555 B
ArmAsm

// 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