[PATCH] D149426: [InstCombine] Fold `(cmp eq/ne (umax X, Y),0)` -> `(cmp eq/ne (or X, Y),0)`

[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.
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`or` is almost always preferable.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149426

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
@@ -812,8 +812,8 @@
 
 define i1 @umax_eq_zero(i8 %x, i8 %y) {
 ; CHECK-LABEL: @umax_eq_zero(
-; CHECK-NEXT:    [[M:%.*]] = call i8 @llvm.umax.i8(i8 [[X:%.*]], i8 [[Y:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[M]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = or i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[TMP1]], 0
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %m = call i8 @llvm.umax.i8(i8 %x, i8 %y)
@@ -845,8 +845,8 @@
 
 define i1 @umax_ne_zero(i8 %x, i8 %y) {
 ; CHECK-LABEL: @umax_ne_zero(
-; CHECK-NEXT:    [[M:%.*]] = call i8 @llvm.umax.i8(i8 [[X:%.*]], i8 [[Y:%.*]])
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[M]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = or i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i8 [[TMP1]], 0
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %m = call i8 @llvm.umax.i8(i8 %x, i8 %y)
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3384,8 +3384,10 @@
     }
     break;
 
+  case Intrinsic::umax:
   case Intrinsic::uadd_sat: {
     // uadd.sat(a, b) == 0  ->  (a | b) == 0
+    // umax(a, b) == 0  ->  (a | b) == 0
     if (C.isZero() && II->hasOneUse()) {
       Value *Or = Builder.CreateOr(II->getArgOperand(0), II->getArgOperand(1));
       return new ICmpInst(Pred, Or, Constant::getNullValue(Ty));


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