diff --git a/llvm/include/llvm/IR/IRBuilder.h b/llvm/include/llvm/IR/IRBuilder.h
--- a/llvm/include/llvm/IR/IRBuilder.h
+++ b/llvm/include/llvm/IR/IRBuilder.h
@@ -259,6 +259,7 @@
     assert(BB && "Must have a basic block to set any function attributes!");
 
     Function *F = BB->getParent();
+    assert(F && "Must have a function to set any function attributes!");
     if (!F->hasFnAttribute(Attribute::StrictFP)) {
       F->addFnAttr(Attribute::StrictFP);
     }
@@ -267,7 +268,6 @@
   void setConstrainedFPCallAttr(CallInst *I) {
     if (!I->hasFnAttr(Attribute::StrictFP))
       I->addAttribute(AttributeList::FunctionIndex, Attribute::StrictFP);
-    setConstrainedFPFunctionAttr();
   }
 
   //===--------------------------------------------------------------------===//
diff --git a/llvm/unittests/IR/IRBuilderTest.cpp b/llvm/unittests/IR/IRBuilderTest.cpp
--- a/llvm/unittests/IR/IRBuilderTest.cpp
+++ b/llvm/unittests/IR/IRBuilderTest.cpp
@@ -233,7 +233,8 @@
   AttributeSet CallAttrs = II->getAttributes().getFnAttributes();
   EXPECT_EQ(CallAttrs.hasAttribute(Attribute::StrictFP), true);
 
-  // Verify attributes on the containing function are created automatically.
+  // Verify attributes on the containing function are created when requested.
+  Builder.setConstrainedFPFunctionAttr();
   AttributeList Attrs = BB->getParent()->getAttributes();
   AttributeSet FnAttrs = Attrs.getFnAttributes();
   EXPECT_EQ(FnAttrs.hasAttribute(Attribute::StrictFP), true);