ConstRange: exhaustively test makeExactICmpRegion (#127058)

Exhaustively test makeExactICmpRegion by comparing makeAllowedICmpRegion
against makeSatisfyingICmpRegion for all APInts.

Author: artagnon

llvm/lib/IR/ConstantRange.cpp

@@ -170,11 +170,10 @@ ConstantRange ConstantRange::makeExactICmpRegion(CmpInst::Predicate Pred,
                                                  const APInt &C) {
   // Computes the exact range that is equal to both the constant ranges returned
   // by makeAllowedICmpRegion and makeSatisfyingICmpRegion. This is always true
-  // when RHS is a singleton such as an APInt and so the assert is valid.
-  // However for non-singleton RHS, for example ult [2,5) makeAllowedICmpRegion
-  // returns [0,4) but makeSatisfyICmpRegion returns [0,2).
+  // when RHS is a singleton such as an APInt. However for non-singleton RHS,
+  // for example ult [2,5) makeAllowedICmpRegion returns [0,4) but
+  // makeSatisfyICmpRegion returns [0,2).
   //
-  assert(makeAllowedICmpRegion(Pred, C) == makeSatisfyingICmpRegion(Pred, C));
   return makeAllowedICmpRegion(Pred, C);
 }
 

llvm/unittests/IR/ConstantRangeTest.cpp

@@ -1662,6 +1662,17 @@ TEST(ConstantRange, MakeAllowedICmpRegionEdgeCases) {
                   .isFullSet());
 }
 
+TEST(ConstantRange, MakeExactICmpRegion) {
+  for (unsigned Bits : {1, 4}) {
+    EnumerateAPInts(Bits, [](const APInt &N) {
+      for (auto Pred : ICmpInst::predicates()) {
+        EXPECT_EQ(ConstantRange::makeAllowedICmpRegion(Pred, N),
+                  ConstantRange::makeSatisfyingICmpRegion(Pred, N));
+      };
+    });
+  }
+}
+
 TEST(ConstantRange, MakeSatisfyingICmpRegion) {
   ConstantRange LowHalf(APInt(8, 0), APInt(8, 128));
   ConstantRange HighHalf(APInt(8, 128), APInt(8, 0));