[clang] [Clang] add wraps and no_wraps attributes (PR #115094)

[Justin Stitt via cfe-commits]

================
@@ -10818,11 +10819,39 @@ static bool IsImplicitBoolFloatConversion(Sema &S, Expr *Ex, bool ToBool) {
           FloatCandidateBT && (FloatCandidateBT->isFloatingPoint()));
 }
 
+/// Check to see if the wraps or no_wraps attribute may have been lost through
+/// a function call. For cases where we are unsure, assume not.
+static bool IsWrapsAttrLost(Sema &S, const CallExpr *TheCall,
+                            const FunctionDecl *FD, unsigned i) {
+  // We may not have a FunctionDecl if this CallExpr is associated virtual,
+  // templated or overloaded functions.
+  if (!FD)
+    return false;
+
+  if (i >= TheCall->getNumArgs() || i >= FD->getNumParams())
+    return false;
+
+  const QualType ProvidedArgTy = TheCall->getArg(i)->getType();
+  const QualType PrototypedArgTy = FD->getParamDecl(i)->getType();
+
+  return (ProvidedArgTy.hasWrapsAttr() && !PrototypedArgTy.hasWrapsAttr()) ||
+         (ProvidedArgTy.hasNoWrapsAttr() && !PrototypedArgTy.hasNoWrapsAttr());
+}
+
 static void CheckImplicitArgumentConversions(Sema &S, CallExpr *TheCall,
                                              SourceLocation CC) {
   unsigned NumArgs = TheCall->getNumArgs();
+  const FunctionDecl *FD = TheCall->getDirectCallee();
+
   for (unsigned i = 0; i < NumArgs; ++i) {
     Expr *CurrA = TheCall->getArg(i);
+
+    if (IsWrapsAttrLost(S, TheCall, FD, i))
----------------
JustinStitt wrote:


> This is looking an AWFUL lot like this needing to be a type with a defined conversion. 

Do you mean make `wraps` or `no_wraps` a type in the same way that [ext_vector_type](https://clang.llvm.org/docs/LanguageExtensions.html#vectors-and-extended-vectors) works? Or even BTFTagAttributedType?


https://github.com/llvm/llvm-project/pull/115094