[PATCH] D149425: [InstCombine] Don't fold `uadd.sat` to `or` if it increase instruction count

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n created this revision.
goldstein.w.n added reviewers: nikic, spatel.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
goldstein.w.n requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

In the `(cmp eq/ne (uadd.sat X, Y),0)` case, we where missing a
`hasOneUse` check.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149425

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/cmp-intrinsic.ll


Index: llvm/test/Transforms/InstCombine/cmp-intrinsic.ll
===================================================================
--- llvm/test/Transforms/InstCombine/cmp-intrinsic.ll
+++ llvm/test/Transforms/InstCombine/cmp-intrinsic.ll
@@ -872,8 +872,7 @@
 ; CHECK-LABEL: @uadd_sat_ne_zero_fail_multiuse(
 ; CHECK-NEXT:    [[M:%.*]] = call i8 @llvm.uadd.sat.i8(i8 [[X:%.*]], i8 [[Y:%.*]])
 ; CHECK-NEXT:    call void @use8(i8 [[M]])
-; CHECK-NEXT:    [[TMP1:%.*]] = or i8 [[X]], [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[TMP1]], 0
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[M]], 0
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %m = call i8 @llvm.uadd.sat.i8(i8 %x, i8 %y)
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3386,7 +3386,7 @@
 
   case Intrinsic::uadd_sat: {
     // uadd.sat(a, b) == 0  ->  (a | b) == 0
-    if (C.isZero()) {
+    if (C.isZero() && II->hasOneUse()) {
       Value *Or = Builder.CreateOr(II->getArgOperand(0), II->getArgOperand(1));
       return new ICmpInst(Pred, Or, Constant::getNullValue(Ty));
     }


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D149425.517809.patch
Type: text/x-patch
Size: 1238 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230428/92a0a768/attachment.bin>