[clang] Fix the signature for __builtin___clear_cache (PR #134376)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman created https://github.com/llvm/llvm-project/pull/134376

The signature was changed from void(char *, char *) to void(void *, void *) to match GCC's signature for the same builtin.

Fixes #47833

>From e37b125713c436d88b49516a1adbbff7c78154c3 Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Fri, 4 Apr 2025 09:02:35 -0400
Subject: [PATCH] Fix the signature for __builtin___clear_cache

The signature was changed from void(char *, char *) to
void(void *, void *) to match GCC's signature for the same builtin.

Fixes #47833
---
 clang/docs/ReleaseNotes.rst           |  4 ++++
 clang/include/clang/Basic/Builtins.td |  2 +-
 clang/test/Sema/clear_cache.c         | 12 ++++++++++++
 3 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/Sema/clear_cache.c

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 3055394dd8b6c..969bfb04623ed 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -354,6 +354,10 @@ Bug Fixes to Compiler Builtins
 
 - The behvaiour of ``__add_pointer`` and ``__remove_pointer`` for Objective-C++'s ``id`` and interfaces has been fixed.
 
+- The signature for ``__builtin___clear_cache`` was changed from
+  ``void(char *, char *)`` to ``void(void *, void *)`` to match GCC's signature
+  for the same builtin. (#GH47833)
+
 Bug Fixes to Attribute Support
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  - Fixed crash when a parameter to the ``clang::annotate`` attribute evaluates to ``void``. See #GH119125
diff --git a/clang/include/clang/Basic/Builtins.td b/clang/include/clang/Basic/Builtins.td
index b2c7ddb43de55..868e5b92acdc9 100644
--- a/clang/include/clang/Basic/Builtins.td
+++ b/clang/include/clang/Basic/Builtins.td
@@ -920,7 +920,7 @@ def FrameAddress : Builtin {
 def ClearCache : Builtin {
   let Spellings = ["__builtin___clear_cache"];
   let Attributes = [NoThrow];
-  let Prototype = "void(char*, char*)";
+  let Prototype = "void(void*, void*)";
 }
 
 def BuiltinSetjmp : Builtin {
diff --git a/clang/test/Sema/clear_cache.c b/clang/test/Sema/clear_cache.c
new file mode 100644
index 0000000000000..e6a3421309967
--- /dev/null
+++ b/clang/test/Sema/clear_cache.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+// Ensure that __builtin___clear_cache has the expected signature. Clang used
+// to have a signature accepting char * while GCC had a signature accepting
+// void * that was documented incorrectly.
+void test(void) {
+ int n = 0;
+  __builtin___clear_cache(&n, &n + 1); // Ok
+  
+  __builtin___clear_cache((const void *)&n, (const void *)(&n + 1)); // expected-warning 2 {{passing 'const void *' to parameter of type 'void *' discards qualifiers}}
+}
+