[llvm] f4e9df2 - [InstCombine] Add test for missed select fold due to one use limitation (NFC)

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-02-22T17:57:00+01:00
New Revision: f4e9df22b5c59692f79fb4d5f9da07d139f6d5aa

URL: https://github.com/llvm/llvm-project/commit/f4e9df22b5c59692f79fb4d5f9da07d139f6d5aa
DIFF: https://github.com/llvm/llvm-project/commit/f4e9df22b5c59692f79fb4d5f9da07d139f6d5aa.diff

LOG: [InstCombine] Add test for missed select fold due to one use limitation (NFC)

The eq sub zero fold currently has an artificial one-use limitation,
causing us to miss this fold.

Added: 
    

Modified: 
    llvm/test/Transforms/InstCombine/icmp-sub.ll

Removed: 
    


################################################################################
diff  --git a/llvm/test/Transforms/InstCombine/icmp-sub.ll b/llvm/test/Transforms/InstCombine/icmp-sub.ll
index 5088cb5a73d1f..2efa2bbe269ad 100644
--- a/llvm/test/Transforms/InstCombine/icmp-sub.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-sub.ll
@@ -488,3 +488,18 @@ define <2 x i1> @sub_ne_zero_use(<2 x i8> %x, <2 x i8> %y) {
   %r = icmp eq <2 x i8> %sub, zeroinitializer
   ret <2 x i1> %r
 }
+
+define i32 @sub_eq_zero_select(i32 %a, i32 %b, i32* %p) {
+; CHECK-LABEL: @sub_eq_zero_select(
+; CHECK-NEXT:    [[SUB:%.*]] = sub i32 [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    store i32 [[SUB]], i32* [[P:%.*]], align 4
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[SUB]], 0
+; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i32 [[A]], i32 [[B]]
+; CHECK-NEXT:    ret i32 [[SEL]]
+;
+  %sub = sub i32 %a, %b
+  store i32 %sub, i32* %p
+  %cmp = icmp eq i32 %sub, 0
+  %sel = select i1 %cmp, i32 %a, i32 %b
+  ret i32 %sel
+}