[SCCP] Skip computing intrinsics if one of its args is unknownOrUndef

For constant range supported intrinsics, we got consantrange from args
no matter if they are unknown or undef. And the constant range computed
from unknown or undef value state is full range.

I think compute with full constant range is harmful since although we
can do mergeIn after these args value state are changed, the merge
operation of two constant ranges is union.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D152499

Author: luxufan

llvm/lib/Transforms/Utils/SCCPSolver.cpp

@@ -1779,6 +1779,8 @@ void SCCPInstVisitor::handleCallResult(CallBase &CB) {
       SmallVector<ConstantRange, 2> OpRanges;
       for (Value *Op : II->args()) {
         const ValueLatticeElement &State = getValueState(Op);
+        if (State.isUnknownOrUndef())
+          return;
         OpRanges.push_back(getConstantRange(State, Op->getType()));
       }
 

llvm/test/Transforms/SCCP/intrinsics.ll

@@ -107,8 +107,7 @@ define i8 @umax_including_undef(i1 %c.1, i1 %c.2) {
 ; CHECK:       false:
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
-; CHECK-NEXT:    [[P_UMAX:%.*]] = call i8 @llvm.umax.i8(i8 3, i8 1)
-; CHECK-NEXT:    ret i8 [[P_UMAX]]
+; CHECK-NEXT:    ret i8 3
 ;
   br i1 %c.1, label %true, label %false