[llvm][DiagnosticInfo] handle function pointer casts

[nickdesaulniers]

Summary

As pointed out by @arsenm in https://reviews.llvm.org/D141451#4045099,
we don't handle ConstantExpressions for dontcall-{warn|error} IR Fn
Attrs.

Use CallBase::getCalledOperand() and Value::stripPointerCasts() should
the call to CallBase::getCalledFunction return nullptr.

I don't know how to express the IR test case in C, otherwise I'd add a
clang test, too.

[aeubanks]

llvm/lib/IR/DiagnosticInfo.cpp

419–421

directly use dyn_cast<Function>(CI.getCalledOperand()->stripPointerCasts()) here?

[arsenm]

Alias has the same problem and is more easily expressive from C

llvm/lib/IR/DiagnosticInfo.cpp

419–421

StripPointerCastsAndAliases?

[nickdesaulniers]

llvm/lib/IR/DiagnosticInfo.cpp

419–421

Alias has the same problem and is more easily expressive from C
StripPointerCastsAndAliases?

Right, but repeating https://reviews.llvm.org/D141451#4063151:

I actually disagree about aliases. I don't think aliases should implicitly inherit function attributes.

[nickdesaulniers]

• just start with dyn_cast, as per @auebanks

[aeubanks]

llvm/test/CodeGen/X86/attr-dontcall.ll

25

we still want this {{$}}

[nickdesaulniers]

• restore end of line check as per @auebanks

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

 
 void SelectionDAGBuilder::visitCall(const CallInst &I) {
   // Handle inline assembly differently.
   if (I.isInlineAsm()) {
     visitInlineAsm(I);
     return;
   }
 
-  if (Function *F = I.getCalledFunction()) {
-    diagnoseDontCall(I);
 
+  if (Function *F = I.getCalledFunction()) {
     if (F->isDeclaration()) {
       // Is this an LLVM intrinsic or a target-specific intrinsic?
       unsigned IID = F->getIntrinsicID();
       if (!IID)
         if (const TargetIntrinsicInfo *II = TM.getIntrinsicInfo())
           IID = II->getIntrinsicID(F);
 
       if (IID) {

llvm/lib/IR/DiagnosticInfo.cpp

 void DiagnosticInfoMisExpect::print(DiagnosticPrinter &DP) const {
   DP << getLocationStr() << ": " << getMsg();
 }
 
 void OptimizationRemarkAnalysisFPCommute::anchor() {}
 void OptimizationRemarkAnalysisAliasing::anchor() {}
 
 void llvm::diagnoseDontCall(const CallInst &CI) {
-  auto *F = CI.getCalledFunction();
+  const auto *F =
+      dyn_cast<Function>(CI.getCalledOperand()->stripPointerCasts());
+
   if (!F)
     return;
 
   for (int i = 0; i != 2; ++i) {
     auto AttrName = i == 0 ? "dontcall-error" : "dontcall-warn";
     auto Sev = i == 0 ? DS_Error : DS_Warning;
 
     if (F->hasFnAttribute(AttrName)) {

llvm/test/CodeGen/X86/attr-dontcall.ll

 }
 
 declare void @foo3() "dontcall-warn"
 define void @bar3() {
   call void @foo3()
   ret void
 }
 
+declare void @foo4(i32) addrspace(1) "dontcall-warn"="cast"
+
+define void @bar4() {
+  call void addrspacecast (ptr addrspace(1) @foo4 to ptr)(i32 0)
+  ret void
+}
+
 ; CHECK: error: call to foo marked "dontcall-error": e
 ; CHECK: warning: call to foo2 marked "dontcall-warn": w
 ; CHECK: warning: call to foo3 marked "dontcall-warn"{{$}}
+; CHECK: warning: call to foo4 marked "dontcall-warn": cast