[ConstantRange] Introduce getMinSignedBits() method

Similar to the ConstantRange::getActiveBits(), and to similarly-named
methods in APInt, returns the bitwidth needed to represent
the given signed constant range

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/unittests/IR/ConstantRangeTest.cpp b/llvm/unittests/IR/ConstantRangeTest.cpp
index 6962d34..19474ee 100644
--- a/llvm/unittests/IR/ConstantRangeTest.cpp
+++ b/llvm/unittests/IR/ConstantRangeTest.cpp
@@ -668,6 +668,32 @@ TEST_F(ConstantRangeTest, losslessUnsignedTruncationZeroext) {
   });
 }
 
+TEST_F(ConstantRangeTest, getMinSignedBits) {
+  unsigned Bits = 4;
+  EnumerateConstantRanges(Bits, [&](const ConstantRange &CR) {
+    unsigned Exact = 0;
+    ForeachNumInConstantRange(CR, [&](const APInt &N) {
+      Exact = std::max(Exact, N.getMinSignedBits());
+    });
+
+    unsigned ResultCR = CR.getMinSignedBits();
+    EXPECT_EQ(Exact, ResultCR);
+  });
+}
+TEST_F(ConstantRangeTest, losslessSignedTruncationSignext) {
+  unsigned Bits = 4;
+  EnumerateConstantRanges(Bits, [&](const ConstantRange &CR) {
+    unsigned MinBitWidth = CR.getMinSignedBits();
+    if (MinBitWidth == 0) {
+      EXPECT_TRUE(CR.isEmptySet());
+      return;
+    }
+    if (MinBitWidth == Bits)
+      return;
+    EXPECT_EQ(CR, CR.truncate(MinBitWidth).signExtend(Bits));
+  });
+}
+
 TEST_F(ConstantRangeTest, SubtractAPInt) {
   EXPECT_EQ(Full.subtract(APInt(16, 4)), Full);
   EXPECT_EQ(Empty.subtract(APInt(16, 4)), Empty);