[llvm-branch-commits] [AllocToken, Clang] Infer type hints from sizeof expressions and casts (PR #156841)

[Florian Mayer via llvm-branch-commits]

================
@@ -1349,6 +1350,98 @@ void CodeGenFunction::EmitAllocTokenHint(llvm::CallBase *CB,
   CB->setMetadata(llvm::LLVMContext::MD_alloc_token_hint, MDN);
 }
 
+/// Infer type from a simple sizeof expression.
+static QualType inferTypeFromSizeofExpr(const Expr *E) {
+  const Expr *Arg = E->IgnoreParenImpCasts();
+  if (const auto *UET = dyn_cast<UnaryExprOrTypeTraitExpr>(Arg)) {
+    if (UET->getKind() == UETT_SizeOf) {
+      if (UET->isArgumentType()) {
+        return UET->getArgumentTypeInfo()->getType();
+      } else {
+        return UET->getArgumentExpr()->getType();
+      }
+    }
+  }
+  return QualType();
+}
+
+/// Infer type from an arithmetic expression involving a sizeof.
+static QualType inferTypeFromArithSizeofExpr(const Expr *E) {
+  const Expr *Arg = E->IgnoreParenImpCasts();
+  // The argument is a lone sizeof expression.
+  QualType QT = inferTypeFromSizeofExpr(Arg);
----------------
fmayer wrote:

```
if (QualType QT = inferTypeFromSizeofExpr(Arg); !QT.isNull())
  return QT;
```

and below

https://github.com/llvm/llvm-project/pull/156841