Index: llvm/include/llvm/ADT/APInt.h
===================================================================
--- llvm/include/llvm/ADT/APInt.h
+++ llvm/include/llvm/ADT/APInt.h
@@ -605,7 +605,7 @@
   /// \returns An APInt value with the requested bits set.
   static APInt getBitsSet(unsigned numBits, unsigned loBit, unsigned hiBit) {
     APInt Res(numBits, 0);
-    Res.setBits(loBit, hiBit);
+    Res.setBitsWithWrap(loBit, hiBit);
     return Res;
   }
 
@@ -1431,6 +1431,21 @@
   }
 
   /// Set the bits from loBit (inclusive) to hiBit (exclusive) to 1.
+  /// This function handles "wrap" case when \p loBit > \p hiBit, and calls  
+  /// setBits when \p loBit <= \p hiBit.
+  void setBitsWithWrap(unsigned loBit, unsigned hiBit) {
+    assert(hiBit <= BitWidth && "hiBit out of range");
+    assert(loBit <= BitWidth && "loBit out of range");
+    if (loBit > hiBit) {
+      setLowBits(hiBit);
+      setHighBits(BitWidth - loBit);
+      return;
+    }
+    setBits(loBit, hiBit);
+  }
+
+  /// Set the bits from loBit (inclusive) to hiBit (exclusive) to 1.
+  /// This function handles case when \p loBit <= \p hiBit.
   void setBits(unsigned loBit, unsigned hiBit) {
     assert(hiBit <= BitWidth && "hiBit out of range");
     assert(loBit <= BitWidth && "loBit out of range");
Index: llvm/unittests/ADT/APIntTest.cpp
===================================================================
--- llvm/unittests/ADT/APIntTest.cpp
+++ llvm/unittests/ADT/APIntTest.cpp
@@ -2044,6 +2044,22 @@
   EXPECT_EQ(1u, i127hi1lo1.countTrailingZeros());
   EXPECT_EQ(0u, i127hi1lo1.countTrailingOnes());
   EXPECT_EQ(125u, i127hi1lo1.countPopulation());
+
+  APInt i64hi1lo1wrap = APInt::getBitsSet(64, 63, 1);
+  EXPECT_EQ(1u, i64hi1lo1wrap.countLeadingOnes());
+  EXPECT_EQ(0u, i64hi1lo1wrap.countLeadingZeros());
+  EXPECT_EQ(64u, i64hi1lo1wrap.getActiveBits());
+  EXPECT_EQ(0u, i64hi1lo1wrap.countTrailingZeros());
+  EXPECT_EQ(1u, i64hi1lo1wrap.countTrailingOnes());
+  EXPECT_EQ(2u, i64hi1lo1wrap.countPopulation());
+
+  APInt i127hi1lo1wrap = APInt::getBitsSet(127, 126, 1);
+  EXPECT_EQ(1u, i127hi1lo1wrap.countLeadingOnes());
+  EXPECT_EQ(0u, i127hi1lo1wrap.countLeadingZeros());
+  EXPECT_EQ(127u, i127hi1lo1wrap.getActiveBits());
+  EXPECT_EQ(0u, i127hi1lo1wrap.countTrailingZeros());
+  EXPECT_EQ(1u, i127hi1lo1wrap.countTrailingOnes());
+  EXPECT_EQ(2u, i127hi1lo1wrap.countPopulation());
 }
 
 TEST(APIntTest, getHighBitsSet) {