[PATCH] D159062: [InstCombine] Folding multiuse `(icmp eq/ne (or X, Y), Y)` for 2 uses of `Y`

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n created this revision.
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The fold will replace 2 uses of `Y` we should also do fold if `Y` has
2 uses (not only oneuse).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159062

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/icmp-of-or-x.ll


Index: llvm/test/Transforms/InstCombine/icmp-of-or-x.ll
===================================================================
--- llvm/test/Transforms/InstCombine/icmp-of-or-x.ll
+++ llvm/test/Transforms/InstCombine/icmp-of-or-x.ll
@@ -380,10 +380,9 @@
 
 define i1 @icmp_eq_x_invertable_y2_todo(i8 %x, i1 %y, i8 %z) {
 ; CHECK-LABEL: @icmp_eq_x_invertable_y2_todo(
-; CHECK-NEXT:    [[ZZ:%.*]] = xor i8 [[Z:%.*]], -1
-; CHECK-NEXT:    [[YY:%.*]] = select i1 [[Y:%.*]], i8 7, i8 [[ZZ]]
-; CHECK-NEXT:    [[OR:%.*]] = or i8 [[YY]], [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[YY]], [[OR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[Y:%.*]], i8 -8, i8 [[Z:%.*]]
+; CHECK-NEXT:    [[TMP2:%.*]] = and i8 [[TMP1]], [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[TMP2]], 0
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zz = xor i8 %z, -1
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4666,7 +4666,7 @@
 
   if (ICmpInst::isEquality(Pred) && Op0->hasOneUse()) {
     // icmp (X | Y) eq/ne Y --> (X & ~Y) eq/ne 0 if Y is freely invertible
-    if (IC.isFreeToInvert(Op1, Op1->hasOneUse()))
+    if (IC.isFreeToInvert(Op1, Op1->hasOneUse() || Op1->hasNUses(2)))
       return new ICmpInst(Pred,
                           IC.Builder.CreateAnd(A, IC.Builder.CreateNot(Op1)),
                           Constant::getNullValue(Op1->getType()));


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