[NFC] Prefer ConstantRange::makeExactICmpRegion over makeAllowedICmpRegion

The implementation is identical, but it makes the semantics a bit more
obvious.

Author: efriedma-quic

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -11369,7 +11369,7 @@ bool ScalarEvolution::isImpliedCondOperandsViaRanges(ICmpInst::Predicate Pred,
   // `FoundLHSRange` is the range we know `FoundLHS` to be in by virtue of the
   // antecedent "`FoundLHS` `Pred` `FoundRHS`".
   ConstantRange FoundLHSRange =
-      ConstantRange::makeAllowedICmpRegion(Pred, ConstFoundRHS);
+      ConstantRange::makeExactICmpRegion(Pred, ConstFoundRHS);
 
   // Since `LHS` is `FoundLHS` + `Addend`, we can compute a range for `LHS`:
   ConstantRange LHSRange = FoundLHSRange.add(ConstantRange(*Addend));

llvm/lib/Analysis/ValueTracking.cpp

@@ -6465,8 +6465,7 @@ isImpliedCondMatchingImmOperands(CmpInst::Predicate APred,
                                  const ConstantInt *C2) {
   ConstantRange DomCR =
       ConstantRange::makeExactICmpRegion(APred, C1->getValue());
-  ConstantRange CR =
-      ConstantRange::makeAllowedICmpRegion(BPred, C2->getValue());
+  ConstantRange CR = ConstantRange::makeExactICmpRegion(BPred, C2->getValue());
   ConstantRange Intersection = DomCR.intersectWith(CR);
   ConstantRange Difference = DomCR.difference(CR);
   if (Intersection.isEmptySet())

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -1497,7 +1497,7 @@ Instruction *InstCombinerImpl::foldICmpWithDominatingICmp(ICmpInst &Cmp) {
     //   br DomCond, CmpBB, FalseBB
     // CmpBB:
     //   Cmp = icmp Pred X, C
-    ConstantRange CR = ConstantRange::makeAllowedICmpRegion(Pred, *C);
+    ConstantRange CR = ConstantRange::makeExactICmpRegion(Pred, *C);
     ConstantRange DominatingCR =
         (CmpBB == TrueBB) ? ConstantRange::makeExactICmpRegion(DomPred, *DomC)
                           : ConstantRange::makeExactICmpRegion(

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

@@ -621,8 +621,8 @@ struct ConstantComparesGatherer {
     }
 
     // If we have "x ult 3", for example, then we can add 0,1,2 to the set.
-    ConstantRange Span = ConstantRange::makeAllowedICmpRegion(
-        ICI->getPredicate(), C->getValue());
+    ConstantRange Span =
+        ConstantRange::makeExactICmpRegion(ICI->getPredicate(), C->getValue());
 
     // Shift the range if the compare is fed by an add. This is the range
     // compare idiom as emitted by instcombine.