[KnownBits] Make use of KnownBits.isUnknown. NFC.

Author: jayfoad

llvm/lib/Analysis/ValueTracking.cpp

@@ -1621,7 +1621,7 @@ static void computeKnownBitsFromOperator(const Operator *I,
 
     // Otherwise take the unions of the known bit sets of the operands,
     // taking conservative care to avoid excessive recursion.
-    if (Depth < MaxAnalysisRecursionDepth - 1 && !Known.Zero && !Known.One) {
+    if (Depth < MaxAnalysisRecursionDepth - 1 && Known.isUnknown()) {
       // Skip if every incoming value references to ourself.
       if (isa_and_nonnull<UndefValue>(P->hasConstantValue()))
         break;

llvm/lib/CodeGen/GlobalISel/GISelKnownBits.cpp

@@ -238,7 +238,7 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known,
         Known = KnownBits::commonBits(Known, Known2);
         // If we reach a point where we don't know anything
         // just stop looking through the operands.
-        if (Known.One == 0 && Known.Zero == 0)
+        if (Known.isUnknown())
           break;
       } else {
         // We know nothing.