[clang] [CIR] Upstream minimal builtin function call support (PR #142981)

[Andy Kaylor via cfe-commits]

================
@@ -1004,8 +1004,48 @@ static cir::FuncOp emitFunctionDeclPointer(CIRGenModule &cgm, GlobalDecl gd) {
   return cgm.getAddrOfFunction(gd);
 }
 
-static CIRGenCallee emitDirectCallee(CIRGenModule &cgm, GlobalDecl gd) {
-  assert(!cir::MissingFeatures::opCallBuiltinFunc());
----------------
andykaylor wrote:

I believe you've removed all instances of this MissingFeature. It should be removed from the header.

https://github.com/llvm/llvm-project/pull/142981