[release-branch.go1.17] cmd/compile: fix fuse pass to do CFG surgery correctly

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 #49129

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>
(cherry picked from commit 8dbf3e9393400d72d313e5616c88873e07692c70)
Reviewed-on: https://go-review.googlesource.com/c/go/+/358118
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/test/fixedbugs/issue49122.go b/test/fixedbugs/issue49122.go
new file mode 100644
index 0000000000..c62a627dae
--- /dev/null
+++ b/test/fixedbugs/issue49122.go
@@ -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]
+}