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

[goldstein.w.n]

Summary

The fold will replace 2 uses of Y we should also do fold if Y has
2 uses (not only oneuse).

[nikic]

LGTM

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

4666

This would be the usual pattern...

[goldstein.w.n]

Rebase

[goldstein.w.n]

Update with nikic's suggestion

[goldstein.w.n]

Abandoning and resubmitting on GH

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

if (Pred == ICmpInst::ICMP_ULE)
     return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
 
   // icmp (X | Y) u> X --> (X | Y) != X
   if (Pred == ICmpInst::ICMP_UGT)
     return new ICmpInst(ICmpInst::ICMP_NE, Op0, Op1);
 
   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->hasNUsesOrMore(3)))
       return new ICmpInst(Pred,
                           IC.Builder.CreateAnd(A, IC.Builder.CreateNot(Op1)),
                           Constant::getNullValue(Op1->getType()));
     // icmp (X | Y) eq/ne Y --> (~X | Y) eq/ne -1 if X  is freely invertible.
     if (IC.isFreeToInvert(A, A->hasOneUse()))
       return new ICmpInst(Pred,
                           IC.Builder.CreateOr(Op1, IC.Builder.CreateNot(A)),
                           Constant::getAllOnesValue(Op1->getType()));

llvm/test/Transforms/InstCombine/icmp-of-or-x.ll

;
   %s = select i1 %v, i32 74, i32 0
   %or = or i32 %s, 1
   %r = icmp ugt i32 %or, %s
   ret i1 %r
 }
 
 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
   %yy = select i1 %y, i8 7, i8 %zz
   %or = or i8 %x, %yy
   %r = icmp eq i8 %yy, %or
   ret i1 %r
 }