Index: llvm/include/llvm/ADT/APInt.h
===================================================================
--- llvm/include/llvm/ADT/APInt.h
+++ llvm/include/llvm/ADT/APInt.h
@@ -1391,6 +1391,12 @@
   /// than or equal to the current width.
   APInt zext(unsigned width) const;
 
+  /// Truncate to width
+  ///
+  /// Make this APInt have the bit width given by \p width. The value is
+  /// truncated or left alone to make it that width.
+  APInt truncOrSelf(unsigned width) const;
+
   /// Sign extend or truncate to width
   ///
   /// Make this APInt have the bit width given by \p width. The value is sign
Index: llvm/lib/Support/APInt.cpp
===================================================================
--- llvm/lib/Support/APInt.cpp
+++ llvm/lib/Support/APInt.cpp
@@ -945,6 +945,12 @@
   return Result;
 }
 
+APInt APInt::truncOrSelf(unsigned width) const {
+  if (BitWidth > width)
+    return trunc(width);
+  return *this;
+}
+
 APInt APInt::zextOrTrunc(unsigned width) const {
   if (BitWidth < width)
     return zext(width);
Index: llvm/unittests/ADT/APIntTest.cpp
===================================================================
--- llvm/unittests/ADT/APIntTest.cpp
+++ llvm/unittests/ADT/APIntTest.cpp
@@ -2598,6 +2598,13 @@
   EXPECT_EQ(63U, i32_neg1.countPopulation());
 }
 
+TEST(APIntTest, truncOrSelf) {
+  APInt val(32, 0xFFFFFFFF);
+  EXPECT_EQ(0xFFFF, val.truncOrSelf(16));
+  EXPECT_EQ(0xFFFFFFFF, val.truncOrSelf(32));
+  EXPECT_EQ(0xFFFFFFFF, val.truncOrSelf(64));
+}
+
 TEST(APIntTest, multiply) {
   APInt i64(64, 1234);