[release-branch.go1.16] cmd/compile: remove incorrect arm,arm64 CMP->CMN transformations

These can go wrong when one of the operands is the minimum integer value.

Fixes #50866.

Change-Id: I238fe284f60c7ee5aeb9dc9a18e8b1578cdb77d0
Reviewed-on: https://go-review.googlesource.com/c/go/+/381318
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
(cherry picked from commit b7b44b3173f151a2313da7072afd25de80511605)
Reviewed-on: https://go-review.googlesource.com/c/go/+/381475
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/test/fixedbugs/issue50854.go b/test/fixedbugs/issue50854.go
new file mode 100644
index 0000000000..a5be9195f1
--- /dev/null
+++ b/test/fixedbugs/issue50854.go
@@ -0,0 +1,38 @@
+// run
+
+// Copyright 2022 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
+
+// This checks for incorrect application of CMP(-x,y) -> CMN(x,y) in arm and arm64
+
+//go:noinline
+func f(p int64, x, y int64) bool { return -x <= p && p <= y }
+
+//go:noinline
+func g(p int32, x, y int32) bool { return -x <= p && p <= y }
+
+// There are some more complicated patterns involving compares and shifts, try to trigger those.
+
+//go:noinline
+func h(p int64, x, y int64) bool { return -(x<<1) <= p && p <= y }
+
+//go:noinline
+func k(p int32, x, y int32) bool { return -(1<<x) <= p && p <= y }
+
+//go:noinline
+func check(b bool) {
+	if b {
+		return
+	}
+	panic("FAILURE")
+}
+
+func main() {
+	check(f(1, -1<<63, 1<<63-1))
+	check(g(1, -1<<31, 1<<31-1))
+	check(h(1, -1<<62, 1<<63-1))
+	check(k(1, 31, 1<<31-1))
+}