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
@@ -255,6 +255,21 @@
     return DefaultConstrainedRounding;
   }
 
+  void setConstrainedFPFunctionAttr() {
+    assert(BB && "Must have a basic block to set any function attributes!");
+
+    Function *F = BB->getParent();
+    if (!F->hasFnAttribute(Attribute::StrictFP)) {
+      F->addFnAttr(Attribute::StrictFP);
+    }
+  }
+
+  void setConstrainedFPCallAttr(CallInst *I) {
+    if (!I->hasFnAttr(Attribute::StrictFP))
+      I->addAttribute(AttributeList::FunctionIndex, Attribute::StrictFP);
+    setConstrainedFPFunctionAttr();
+  }
+
   //===--------------------------------------------------------------------===//
   // RAII helpers.
   //===--------------------------------------------------------------------===//
@@ -1479,6 +1494,8 @@
 
     CallInst *C = CreateIntrinsic(ID, {L->getType()},
                                   {L, R, RoundingV, ExceptV}, nullptr, Name);
+    setConstrainedFPCallAttr(C);
+
     return cast<CallInst>(setFPAttrs(C, FPMathTag, UseFMF));
   }
 
@@ -2083,6 +2100,8 @@
                           Name);
       break;
     }
+    setConstrainedFPCallAttr(C);
+
     if (isa<FPMathOperator>(C))
       C = cast<CallInst>(setFPAttrs(C, FPMathTag, UseFMF));
     return C;
@@ -2239,6 +2258,8 @@
                        ArrayRef<Value *> Args = None, const Twine &Name = "",
                        MDNode *FPMathTag = nullptr) {
     CallInst *CI = CallInst::Create(FTy, Callee, Args, DefaultOperandBundles);
+    if (IsFPConstrained)
+      setConstrainedFPCallAttr(CI);
     if (isa<FPMathOperator>(CI))
       CI = cast<CallInst>(setFPAttrs(CI, FPMathTag, FMF));
     return Insert(CI, Name);
@@ -2248,6 +2269,8 @@
                        ArrayRef<OperandBundleDef> OpBundles,
                        const Twine &Name = "", MDNode *FPMathTag = nullptr) {
     CallInst *CI = CallInst::Create(FTy, Callee, Args, OpBundles);
+    if (IsFPConstrained)
+      setConstrainedFPCallAttr(CI);
     if (isa<FPMathOperator>(CI))
       CI = cast<CallInst>(setFPAttrs(CI, FPMathTag, FMF));
     return Insert(CI, Name);
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
@@ -229,6 +229,15 @@
   II = cast<IntrinsicInst>(VDouble);
   EXPECT_EQ(II->getIntrinsicID(), Intrinsic::experimental_constrained_fpext);
 
+  // Verify attributes on the call are created automatically.
+  AttributeSet CallAttrs = II->getAttributes().getFnAttributes();
+  EXPECT_EQ(CallAttrs.hasAttribute(Attribute::StrictFP), true);
+
+  // Verify attributes on the containing function are created automatically.
+  AttributeList Attrs = BB->getParent()->getAttributes();
+  AttributeSet FnAttrs = Attrs.getFnAttributes();
+  EXPECT_EQ(FnAttrs.hasAttribute(Attribute::StrictFP), true);
+
   // Verify the codepaths for setting and overriding the default metadata.
   V = Builder.CreateFAdd(V, V);
   ASSERT_TRUE(isa<ConstrainedFPIntrinsic>(V));