From 0680e84a3f2a366a860bd0491f490a2fba800313 Mon Sep 17 00:00:00 2001
From: Andrei Golubev <andrey.golubev@intel.com>
Date: Mon, 29 Jan 2024 10:37:11 +0200
Subject: [PATCH] [mlir] Revert to old fold logic in IR::Dialect::add{Types,
 Attributes}() (#79582)

Fold expressions on Clang are limited to 256 elements. This causes
compilation errors in cases when the amount of elements added exceeds
this limit. Side-step the issue by restoring the original trick that
would use the std::initializer_list. For the record, in our downstream
Clang 16 gives:

mlir/include/mlir/IR/Dialect.h:269:23: fatal error: instantiating fold
expression with 688 arguments exceeded expression nesting limit of 256
    (addType<Args>(), ...);

Partially reverts 26d811b3ecd2fa1ca3d9b41e17fb42b8c7ad03d6.

Co-authored-by: Nikita Kudriavtsev <nikita.kudriavtsev@intel.com>
(cherry picked from commit e3a38a75ddc6ff00301ec19a0e2488d00f2cc297)
---
 mlir/include/mlir/IR/Dialect.h | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/mlir/include/mlir/IR/Dialect.h b/mlir/include/mlir/IR/Dialect.h
index 45f29f37dd3b97..50f6f6de5c2897 100644
--- a/mlir/include/mlir/IR/Dialect.h
+++ b/mlir/include/mlir/IR/Dialect.h
@@ -281,7 +281,11 @@ class Dialect {
   /// Register a set of type classes with this dialect.
   template <typename... Args>
   void addTypes() {
-    (addType<Args>(), ...);
+    // This initializer_list argument pack expansion is essentially equal to
+    // using a fold expression with a comma operator. Clang however, refuses
+    // to compile a fold expression with a depth of more than 256 by default.
+    // There seem to be no such limitations for initializer_list.
+    (void)std::initializer_list<int>{0, (addType<Args>(), 0)...};
   }
 
   /// Register a type instance with this dialect.
@@ -292,7 +296,11 @@ class Dialect {
   /// Register a set of attribute classes with this dialect.
   template <typename... Args>
   void addAttributes() {
-    (addAttribute<Args>(), ...);
+    // This initializer_list argument pack expansion is essentially equal to
+    // using a fold expression with a comma operator. Clang however, refuses
+    // to compile a fold expression with a depth of more than 256 by default.
+    // There seem to be no such limitations for initializer_list.
+    (void)std::initializer_list<int>{0, (addAttribute<Args>(), 0)...};
   }
 
   /// Register an attribute instance with this dialect.