Fix integer undefined behavior due to signed left shift overflow in LLVM.

Reviewed offline by chandlerc.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162623 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 0 deletions

diff --git a/include/llvm/Support/MathExtras.h b/include/llvm/Support/MathExtras.h
index 4005161320..35c2694cff 100644
--- a/include/llvm/Support/MathExtras.h
+++ b/include/llvm/Support/MathExtras.h
@@ -463,12 +463,24 @@ template <unsigned B> inline int32_t SignExtend32(uint32_t x) {
   return int32_t(x << (32 - B)) >> (32 - B);
 }
 
+/// \brief Sign extend number in the bottom B bits of X to a 32-bit int.
+/// Requires 0 < B <= 32.
+inline int32_t SignExtend32(uint32_t X, unsigned B) {
+  return int32_t(X << (32 - B)) >> (32 - B);
+}
+
 /// SignExtend64 - Sign extend B-bit number x to 64-bit int.
 /// Usage int64_t r = SignExtend64<5>(x);
 template <unsigned B> inline int64_t SignExtend64(uint64_t x) {
   return int64_t(x << (64 - B)) >> (64 - B);
 }
 
+/// \brief Sign extend number in the bottom B bits of X to a 64-bit int.
+/// Requires 0 < B <= 64.
+inline int64_t SignExtend64(uint64_t X, unsigned B) {
+  return int64_t(X << (64 - B)) >> (64 - B);
+}
+
 } // End llvm namespace
 
 #endif