diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -13113,6 +13113,8 @@
     return Builder.CreateBitCast(Sext, FPVecTy);
   };
 
+  IRBuilder<>::FastMathFlagGuard FMFGuard(Builder);
+
   switch (BuiltinID) {
   default: return nullptr;
   case X86::BI_mm_prefetch: {