[llvm] [LVI] Generalize mask not equal conditions handling (PR #92946)

[Antonio Frighetto via llvm-commits]

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@@ -2788,4 +2788,52 @@ TEST_F(ConstantRangeTest, isSizeLargerThan) {
   EXPECT_FALSE(One.isSizeLargerThan(1));
 }
 
+TEST_F(ConstantRangeTest, MakeMaskNotEqualRange) {
+  // Mask: 0b0001, C: 0b0001. MMNE() = [2, 1)
+  ConstantRange CR(APInt(4, 2), APInt(4, 1));
+  EXPECT_EQ(CR, ConstantRange::makeMaskNotEqualRange(APInt(4, 1), APInt(4, 1)));
+  EXPECT_NE(CR, ConstantRange::makeMaskNotEqualRange(APInt(4, 0),
+                                                     APInt(4, -1, true)));
+  EXPECT_TRUE(CR.contains(APInt(4, 7)));
+  EXPECT_TRUE(CR.contains(APInt(4, 15)));
+
+  // Mask: 0b0100, C: 0b0100. MMNE() = [-8, 4)
+  ConstantRange CR2(APInt(4, -8, true), APInt(4, 4));
+  auto MMNE = ConstantRange::makeMaskNotEqualRange(APInt(4, 4), APInt(4, 4));
+  EXPECT_EQ(CR2, MMNE);
+  EXPECT_NE(ConstantRange::getNonEmpty(APInt(4, 0), APInt(4, -4, true)), MMNE);
+
+  // CR: [-16, -8). MMNE() = [-8, -16)
+  ConstantRange CR3(APInt(8, 240), APInt(8, 248));
+  EXPECT_EQ(CR3.inverse(),
+            ConstantRange::makeMaskNotEqualRange(APInt(8, 248), APInt(8, 240)));
+
+  // Mask: 0, C: 0b1111: unsatisfiable.
+  EXPECT_EQ(ConstantRange::getFull(4),
+            ConstantRange::makeMaskNotEqualRange(APInt(4, 0), APInt(4, 15)));
+}
+
+TEST_F(ConstantRangeTest, MakeMaskNotEqualRangeExhaustive) {
+  unsigned Bits = 4;
+  unsigned Max = 1 << Bits;
+
+  EnumerateAPInts(Bits, [&](const APInt &Mask) {
+    EnumerateAPInts(Bits, [&](const APInt &C) {
+      SmallBitVector Elems(Max);
+      for (unsigned N = 0; N < Max; ++N) {
+        APInt Num(Bits, N);
+        if ((Num & Mask) == C)
+          continue;
+        Elems.set(Num.getZExtValue());
+      }
+
+      // Do not test optimality. For instance, given Mask = 0b0001, C = 0b0001,
+      // a possible better range would be [0, 15) when preferring the smallest
+      // unsigned, however we conservatively return [2, 1).
+      TestRange(ConstantRange::makeMaskNotEqualRange(Mask, C), Elems,
+                PreferSmallestUnsigned, {}, false);
----------------
antoniofrighetto wrote:

Right, but only due to the fact that we were conservatively returning full-set when `Elems.none()` holded. Now returning empty-set in the only occurring case, so switched to PreferSmallest with optimality set, thanks for noticing it.

https://github.com/llvm/llvm-project/pull/92946