[NFC][KnownBits] Add getMinValue() / getMaxValue() methods

As it can be seen from accompanying cleanup, it is not unheard of
to write `~Known.Zero` meaning "what maximal value can this KnownBits
produce". But i think `~Known.Zero` isn't *that* self-explanatory,
as compared to a method with a name.

Note that not all `~Known.Zero` places were cleaned up,
only those where this arguably improves things.

2 files changed, 6 insertions, 5 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 483159bef98..d635afb0a29 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -5717,10 +5717,11 @@ ScalarEvolution::getRangeRef(const SCEV *S,
     if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED) {
       // For a SCEVUnknown, ask ValueTracking.
       KnownBits Known = computeKnownBits(U->getValue(), DL, 0, &AC, nullptr, &DT);
-      if (Known.One != ~Known.Zero + 1)
-        ConservativeResult =
-            ConservativeResult.intersectWith(
-                ConstantRange(Known.One, ~Known.Zero + 1), RangeType);
+      // If Known does not result in full-set, intersect with it.
+      if (Known.getMinValue() != Known.getMaxValue() + 1)
+        ConservativeResult = ConservativeResult.intersectWith(
+            ConstantRange(Known.getMinValue(), Known.getMaxValue() + 1),
+            RangeType);
     } else {
       assert(SignHint == ScalarEvolution::HINT_RANGE_SIGNED &&
              "generalize as needed!");
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 51d92cca214..f46bae77ba2 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -915,7 +915,7 @@ static void computeKnownBitsFromShiftOperator(
   // If the shift amount could be greater than or equal to the bit-width of the
   // LHS, the value could be poison, but bail out because the check below is
   // expensive. TODO: Should we just carry on?
-  if ((~Known.Zero).uge(BitWidth)) {
+  if (Known.getMaxValue().uge(BitWidth)) {
     Known.resetAll();
     return;
   }