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cmd/compile: fix fuse pass to do CFG surgery correctly

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removePred and removeArg do different things. removePred moves the last
predecessor to index k, whereas removeArg slides all the args k or
greater down by 1 index.

Kind of unfortunate different behavior in things named similarly.

Fixes #49122

Change-Id: I9ae409bdac744e713f4c121f948e43db6fdc8542
Reviewed-on: https://go-review.googlesource.com/c/go/+/358117
Trust: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
This commit is contained in:
Keith Randall 2021-10-23 10:16:41 -07:00
parent 16318df4a2
commit 8dbf3e9393
2 changed files with 21 additions and 1 deletions
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6
src/cmd/compile/internal/ssa/fuse_branchredirect.go
View File

@ -78,7 +78,11 @@ func fuseBranchRedirect(f *Func) bool {
if v.Op != OpPhi {
continue
}
v.RemoveArg(k)
n := len(v.Args)
v.Args[k].Uses--
v.Args[k] = v.Args[n-1]
v.Args[n-1] = nil
v.Args = v.Args[:n-1]
phielimValue(v)
}
// Fix up child to have one more predecessor.

16
test/fixedbugs/issue49122.go Normal file
View File

@ -0,0 +1,16 @@
// compile
// Copyright 2021 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.
package main
var B []bool
var N int
func f(p bool, m map[bool]bool) bool {
var q bool
_ = p || N&N < N || B[0] || B[0]
return p && q && m[q]
}