From: Sanjay Patel <spatel@rotateright.com>
Date: Fri, 22 Jul 2022 20:09:29 +0000 (-0400)
Subject: [PhaseOrdering] add explanatory comment for test; NFC
X-Git-Tag: upstream/15.0.7~635
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=13853cf73035757fa36a410227de9c39c0e9eb26;p=platform%2Fupstream%2Fllvm.git

[PhaseOrdering] add explanatory comment for test; NFC

This note was going to be added in D129650, but we
solved the problem by reverting another patch, and
I missed transferring the comment.
---

diff --git a/llvm/test/Transforms/PhaseOrdering/SystemZ/sub-xor.ll b/llvm/test/Transforms/PhaseOrdering/SystemZ/sub-xor.ll
index 66870d1..23e45bc 100644
--- a/llvm/test/Transforms/PhaseOrdering/SystemZ/sub-xor.ll
+++ b/llvm/test/Transforms/PhaseOrdering/SystemZ/sub-xor.ll
@@ -6,6 +6,11 @@ target triple = "systemz"
 
 @ARR = internal global [100 x i32] zeroinitializer, align 4
 
+; This test uses 'sub' instructions for gep offsets to allow
+; codegen (LSR) to create optimal asm. If 'sub' is canonicalized
+; to 'xor', then the backend needs to be able to see through
+; that transform to produce optimal asm.
+
 define dso_local zeroext i32 @foo(ptr noundef %a) #0 {
 ; CHECK-LABEL: @foo(
 ; CHECK-NEXT:  entry: