[llvm] Add ConstantRangeList::subtract(ConstantRange) (PR #97093)

[Jan Voung via llvm-commits]

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@@ -101,6 +101,50 @@ ConstantRangeList GetCRL(ArrayRef<std::pair<APInt, APInt>> Pairs) {
   return ConstantRangeList(Ranges);
 }
 
+TEST_F(ConstantRangeListTest, Subtract) {
+  APInt AP0 = APInt(64, 0, /*isSigned=*/true);
+  APInt AP2 = APInt(64, 2, /*isSigned=*/true);
+  APInt AP3 = APInt(64, 3, /*isSigned=*/true);
+  APInt AP4 = APInt(64, 4, /*isSigned=*/true);
+  APInt AP8 = APInt(64, 8, /*isSigned=*/true);
+  APInt AP10 = APInt(64, 10, /*isSigned=*/true);
+  APInt AP11 = APInt(64, 11, /*isSigned=*/true);
+  APInt AP12 = APInt(64, 12, /*isSigned=*/true);
+  ConstantRangeList CRL = GetCRL({{AP0, AP4}, {AP8, AP12}});
+
+  // Execute ConstantRangeList::subtract(ConstantRange) and check the result
+  // is expected. Pass "CRL" by value so that subtract() does not affect the
+  // argument in caller.
+  auto SubtractAndCheck = [](ConstantRangeList CRL,
+                             const std::pair<int64_t, int64_t> &Range,
+                             const ConstantRangeList &ExpectedCRL) {
+    CRL.subtract(Range.first, Range.second);
+    EXPECT_EQ(CRL, ExpectedCRL);
+  };
+
+  // No overlap
+  SubtractAndCheck(CRL, {-4, 0}, CRL);
+  SubtractAndCheck(CRL, {4, 8}, CRL);
+  SubtractAndCheck(CRL, {12, 16}, CRL);
+
+  // Overlap (left or right)
+  SubtractAndCheck(CRL, {-4, 2}, GetCRL({{AP2, AP4}, {AP8, AP12}}));
+  SubtractAndCheck(CRL, {-4, 4}, GetCRL({{AP8, AP12}}));
+  SubtractAndCheck(CRL, {-4, 8}, GetCRL({{AP8, AP12}}));
+  SubtractAndCheck(CRL, {10, 16}, GetCRL({{AP0, AP4}, {AP8, AP10}}));
+  SubtractAndCheck(CRL, {8, 16}, GetCRL({{AP0, AP4}}));
+  SubtractAndCheck(CRL, {6, 16}, GetCRL({{AP0, AP4}}));
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jvoung wrote:

maybe try touching at the other ends like {0, X} and {X, 12} too 
(vs {X, 4} and {8, X})?

https://github.com/llvm/llvm-project/pull/97093