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
@@ -294,8 +294,7 @@
   }
 
   void setConstrainedFPCallAttr(CallInst *I) {
-    if (!I->hasFnAttr(Attribute::StrictFP))
-      I->addAttribute(AttributeList::FunctionIndex, Attribute::StrictFP);
+    I->addAttribute(AttributeList::FunctionIndex, Attribute::StrictFP);
   }
 
   void setDefaultOperandBundles(ArrayRef<OperandBundleDef> OpBundles) {
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
@@ -332,6 +332,33 @@
   EXPECT_EQ(fp::ebStrict, CII->getExceptionBehavior());
 }
 
+TEST_F(IRBuilderTest, ConstrainedFPFunctionCall) {
+  IRBuilder<> Builder(BB);
+
+  // Create an empty constrained FP function.
+  FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
+                                        /*isVarArg=*/false);
+  Function *Callee =
+      Function::Create(FTy, Function::ExternalLinkage, "", M.get());
+  BasicBlock *CalleeBB = BasicBlock::Create(Ctx, "", Callee);
+  IRBuilder<> CalleeBuilder(CalleeBB);
+  CalleeBuilder.setIsFPConstrained(true);
+  CalleeBuilder.setConstrainedFPFunctionAttr();
+  CalleeBuilder.CreateRetVoid();
+
+  // Now call the empty constrained FP function.
+  Builder.setIsFPConstrained(true);
+  Builder.setConstrainedFPFunctionAttr();
+  CallInst *FCall = Builder.CreateCall(Callee, None);
+
+  // Check the attributes to verify the strictfp attribute is on the call.
+  EXPECT_TRUE(FCall->getAttributes().getFnAttributes().hasAttribute(
+      Attribute::StrictFP));
+
+  Builder.CreateRetVoid();
+  EXPECT_FALSE(verifyModule(*M));
+}
+
 TEST_F(IRBuilderTest, Lifetime) {
   IRBuilder<> Builder(BB);
   AllocaInst *Var1 = Builder.CreateAlloca(Builder.getInt8Ty());