| // compile |
| |
| // 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. |
| |
| // This tickles (a version of) the PPC64 back end to |
| // emit a BVS instruction. |
| |
| package foo |
| |
| type Flag int |
| |
| const ( |
| Identity Flag = iota - 2 // H is the identity matrix; no rotation is needed. |
| Rescaling // H specifies rescaling. |
| ) |
| |
| type DrotmParams struct { |
| Flag |
| } |
| |
| func Drotmg(d1, d2, x1, y1 float64) (p DrotmParams, rd1, rd2, rx1 float64) { |
| |
| const ( |
| gam = 4.0 |
| gamsq = 16.0 |
| rgamsq = 5e-8 |
| ) |
| |
| if d1 < 0 { |
| p.Flag = Rescaling |
| return |
| } |
| |
| for rd1 <= rgamsq || rd1 >= gamsq { |
| if rd1 <= rgamsq { |
| rd1 *= gam * gam |
| rx1 /= gam |
| } else { |
| rd1 /= gam * gam |
| rx1 *= gam |
| } |
| } |
| return |
| } |
