[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.

1 files changed, 1 insertions, 1 deletions

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;
   }