[clang] nonblocking/nonallocating attributes (was: nolock/noalloc) (PR #84983)

[via cfe-commits]

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@@ -7963,6 +7967,148 @@ static Attr *getCCTypeAttr(ASTContext &Ctx, ParsedAttr &Attr) {
   llvm_unreachable("unexpected attribute kind!");
 }
 
+ExprResult Sema::ActOnEffectExpression(Expr *CondExpr, FunctionEffectMode &Mode,
+                                       bool RequireConstexpr) {
+  // see checkFunctionConditionAttr, Sema::CheckCXXBooleanCondition
+  if (RequireConstexpr || !CondExpr->isTypeDependent()) {
+    ExprResult E = PerformContextuallyConvertToBool(CondExpr);
+    if (E.isInvalid())
+      return E;
+    CondExpr = E.get();
+    if (RequireConstexpr || !CondExpr->isValueDependent()) {
+      llvm::APSInt CondInt;
+      E = VerifyIntegerConstantExpression(
+          E.get(), &CondInt,
+          // TODO: have our own diagnostic
+          diag::err_constexpr_if_condition_expression_is_not_constant);
+      if (E.isInvalid()) {
+        return E;
+      }
+      Mode =
+          (CondInt != 0) ? FunctionEffectMode::True : FunctionEffectMode::False;
+    } else {
+      Mode = FunctionEffectMode::Dependent;
+    }
+  } else {
+    Mode = FunctionEffectMode::Dependent;
+  }
+  return CondExpr;
+}
+
+static bool
+handleNonBlockingNonAllocatingTypeAttr(TypeProcessingState &TPState,
+                                       ParsedAttr &PAttr, QualType &QT,
+                                       FunctionTypeUnwrapper &Unwrapped) {
+  // Delay if this is not a function type.
+  if (!Unwrapped.isFunctionType())
+    return false;
+
+  // Require FunctionProtoType
+  auto *FPT = Unwrapped.get()->getAs<FunctionProtoType>();
+  if (FPT == nullptr) {
+    // TODO: special diagnostic?
+    return false;
+  }
+
+  // Parse the new  attribute.
+  // non/blocking or non/allocating? Or conditional (computed)?
+  const bool isNonBlocking = PAttr.getKind() == ParsedAttr::AT_NonBlocking ||
----------------
Sirraide wrote:

```suggestion
  const bool IsNonBlocking = PAttr.getKind() == ParsedAttr::AT_NonBlocking ||
```
nit

https://github.com/llvm/llvm-project/pull/84983