[FPEnv] IRBuilder fails to add strictfp attribute

[kpn]

Summary

The strictfp attribute is required on all function calls in a function that is itself marked with the strictfp attribute. The IRBuilder knows this and has a method for adding the attribute to function call instructions.

If a function being called has the strictfp attribute itself then the IRBuilder will refuse to add the attribute to the calling instruction despite being asked to add it. Eliminate this error.

[rjmccall]

LGTM.

llvm/include/llvm/IR/IRBuilder.h

void setConstrainedFPFunctionAttr() {
 
     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);
   }
 
   void setDefaultOperandBundles(ArrayRef<OperandBundleDef> OpBundles) {
     DefaultOperandBundles = OpBundles;
   }
 
   //===--------------------------------------------------------------------===//
   // RAII helpers.

llvm/unittests/IR/IRBuilderTest.cpp

TEST_F(IRBuilderTest, ConstrainedFPIntrinsics) {
   Function *Fn = Intrinsic::getDeclaration(M.get(),
       Intrinsic::experimental_constrained_roundeven, { Type::getDoubleTy(Ctx) });
   V = Builder.CreateConstrainedFPCall(Fn, { VDouble });
   CII = cast<ConstrainedFPIntrinsic>(V);
   EXPECT_EQ(Intrinsic::experimental_constrained_roundeven, CII->getIntrinsicID());
   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());
   AllocaInst *Var2 = Builder.CreateAlloca(Builder.getInt32Ty());
   AllocaInst *Var3 = Builder.CreateAlloca(Builder.getInt8Ty(),
                                           Builder.getInt32(123));
 
   CallInst *Start1 = Builder.CreateLifetimeStart(Var1);