From d0964e172b83db45d167b21e93b79fe86b158760 Mon Sep 17 00:00:00 2001
From: Keith Randall <khr@golang.org>
Date: Thu, 15 Jun 2023 09:14:12 -0700
Subject: cmd/compile: optimize s==s for strings

s==s is always true for strings. This comes up in NaN testing in
generic code, where we want x==x to compile completely away except for
float types.

Fixes #60777

Change-Id: I3ce054b5121354de2f9751b010fb409f148cb637
Reviewed-on: https://go-review.googlesource.com/c/go/+/503795
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
---
 test/codegen/strings.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'test/codegen')

diff --git a/test/codegen/strings.go b/test/codegen/strings.go
index 94512f5cd3..f98c062d1b 100644
--- a/test/codegen/strings.go
+++ b/test/codegen/strings.go
@@ -67,4 +67,14 @@ func ConstantLoad() {
 	bsink = []byte("0123456789ab")
 }
 
+// self-equality is always true. See issue 60777.
+func EqualSelf(s string) bool {
+	// amd64:`MOVL\t\$1, AX`,-`.*memequal.*`
+	return s == s
+}
+func NotEqualSelf(s string) bool {
+	// amd64:`XORL\tAX, AX`,-`.*memequal.*`
+	return s != s
+}
+
 var bsink []byte
-- 
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