cmd/compile: compute OR's maximum limits from argument's limits

Change-Id: I6902c405cab7bd573f6a721a6ca7c783713ea39a
Reviewed-on: https://go-review.googlesource.com/c/go/+/604456
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/test/prove.go b/test/prove.go
index 2d5d181aa9..8e65404431 100644
--- a/test/prove.go
+++ b/test/prove.go
@@ -1408,6 +1408,24 @@ func xor64(a, b uint64, ensureBothBranchesCouldHappen bool) int {
 	return int(z)
 }
 
+func or64(a, b uint64, ensureBothBranchesCouldHappen bool) int {
+	a &= 0xff
+	b &= 0xfff
+
+	z := a | b
+
+	if ensureBothBranchesCouldHappen {
+		if z > 0xfff { // ERROR "Disproved Less64U$"
+			return 42
+		}
+	} else {
+		if z <= 0xfff { // ERROR "Proved Leq64U$"
+			return 1337
+		}
+	}
+	return int(z)
+}
+
 //go:noinline
 func useInt(a int) {
 }