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https://github.com/golang/go
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c6118af558
That optimization is not valid if x == -0. The test is a bit tricky because 0 == -0. We distinguish 0 from -0 with 1/0 == inf, 1/-0 == -inf. This has been a bug since CL 24790 in Go 1.8. Probably doesn't warrant a backport. Fixes #27718 Note: the optimization x-0 -> x is actually valid. But it's probably best to take it out, so as to not confuse readers. Change-Id: I99f16a93b45f7406ec8053c2dc759a13eba035fa Reviewed-on: https://go-review.googlesource.com/135701 Reviewed-by: Cherry Zhang <cherryyz@google.com>
73 lines
1.1 KiB
Go
73 lines
1.1 KiB
Go
// run
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// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// (-0)+0 should be 0, not -0.
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package main
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//go:noinline
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func add64(x float64) float64 {
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return x + 0
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}
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func testAdd64() {
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var zero float64
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inf := 1.0 / zero
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negZero := -1 / inf
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if 1/add64(negZero) != inf {
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panic("negZero+0 != posZero (64 bit)")
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}
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}
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//go:noinline
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func sub64(x float64) float64 {
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return x - 0
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}
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func testSub64() {
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var zero float64
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inf := 1.0 / zero
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negZero := -1 / inf
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if 1/sub64(negZero) != -inf {
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panic("negZero-0 != negZero (64 bit)")
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}
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}
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//go:noinline
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func add32(x float32) float32 {
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return x + 0
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}
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func testAdd32() {
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var zero float32
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inf := 1.0 / zero
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negZero := -1 / inf
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if 1/add32(negZero) != inf {
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panic("negZero+0 != posZero (32 bit)")
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}
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}
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//go:noinline
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func sub32(x float32) float32 {
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return x - 0
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}
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func testSub32() {
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var zero float32
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inf := 1.0 / zero
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negZero := -1 / inf
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if 1/sub32(negZero) != -inf {
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panic("negZero-0 != negZero (32 bit)")
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}
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}
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func main() {
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testAdd64()
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testSub64()
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testAdd32()
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testSub32()
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}
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