[llvm] [SCCP] Add support for trunc nuw range. (PR #152990)

[Andreas Jonson via llvm-commits]

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@@ -451,6 +452,69 @@ TEST_F(ConstantRangeTest, Trunc) {
   EXPECT_EQ(SevenOne.truncate(2), ConstantRange(APInt(2, 3), APInt(2, 1)));
 }
 
+TEST_F(ConstantRangeTest, TruncNuw) {
+  auto Range = [](unsigned NumBits, unsigned Lower, unsigned Upper) {
+    return ConstantRange(APInt(NumBits, Lower), APInt(NumBits, Upper));
+  };
+  // trunc([0, 4), 3->2) = full
+  EXPECT_TRUE(
+      Range(3, 0, 4).truncate(2, TruncInst::NoUnsignedWrap).isFullSet());
+  // trunc([0, 3), 3->2) = [0, 3)
+  EXPECT_EQ(Range(3, 0, 3).truncate(2, TruncInst::NoUnsignedWrap),
+            Range(2, 0, 3));
+  // trunc([1, 3), 3->2) = [1, 3)
+  EXPECT_EQ(Range(3, 1, 3).truncate(2, TruncInst::NoUnsignedWrap),
+            Range(2, 1, 3));
+  // trunc([1, 5), 3->2) = [1, 0)
+  EXPECT_EQ(Range(3, 1, 5).truncate(2, TruncInst::NoUnsignedWrap),
+            Range(2, 1, 0));
+  // trunc([4, 7), 3->2) = empty
+  EXPECT_TRUE(
+      Range(3, 4, 7).truncate(2, TruncInst::NoUnsignedWrap).isEmptySet());
+  // trunc([4, 0), 3->2) = empty
+  EXPECT_TRUE(
+      Range(3, 4, 0).truncate(2, TruncInst::NoUnsignedWrap).isEmptySet());
+  // trunc([4, 1), 3->2) = [0, 1)
+  EXPECT_EQ(Range(3, 4, 1).truncate(2, TruncInst::NoUnsignedWrap),
+            Range(2, 0, 1));
+  // trunc([3, 1), 3->2) = [3, 1)
+  EXPECT_EQ(Range(3, 3, 1).truncate(2, TruncInst::NoUnsignedWrap),
+            Range(2, 3, 1));
+  // trunc([3, 0), 3->2) = [3, 0)
+  EXPECT_EQ(Range(3, 3, 0).truncate(2, TruncInst::NoUnsignedWrap),
+            Range(2, 3, 0));
+  // trunc([1, 0), 2->1) = [1, 0)
+  EXPECT_EQ(Range(2, 1, 0).truncate(1, TruncInst::NoUnsignedWrap),
+            Range(1, 1, 0));
+  // trunc([2, 1), 2->1) = [0, 1)
+  EXPECT_EQ(Range(2, 2, 1).truncate(1, TruncInst::NoUnsignedWrap),
+            Range(1, 0, 1));
+}
+
+TEST_F(ConstantRangeTest, TruncNuwExhaustive) {
+  unsigned NumBits = 3;
+  EnumerateConstantRanges(4, [&](const ConstantRange &CR) {
----------------
andjo403 wrote:

change to the suggestion

https://github.com/llvm/llvm-project/pull/152990