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

[goldstein.w.n]

Summary

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

[nikic]

LGTM

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

if (II->getArgOperand(0) == II->getArgOperand(1)) {
                             II->getIntrinsicID() == Intrinsic::fshl
                                 ? ConstantInt::get(Ty, C.rotr(*RotAmtC))
                                 : ConstantInt::get(Ty, C.rotl(*RotAmtC)));
     }
     break;
 
   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));
     }
     break;
   }
 
   case Intrinsic::usub_sat: {
     // usub.sat(a, b) == 0  ->  a <= b

llvm/test/Transforms/InstCombine/cmp-intrinsic.ll

;
   ret i1 %r
 }
 
 
 define i1 @uadd_sat_ne_zero_fail_multiuse(i8 %x, i8 %y) {
 ; 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)
   call void @use8(i8 %m)
   %r = icmp ne i8 %m, 0
   ret i1 %r
 }