[CLANG][BPF] permit any argument type for __builtin_preserve_access_index()

Commit c15aa241f821 ("[CLANG][BPF] change __builtin_preserve_access_index()
signature") changed the builtin function signature to
  PointerT __builtin_preserve_access_index(PointerT ptr)
with a pointer type as the argument/return type, where argument and
return types must be the same.

There is really no reason for this constraint. The builtin just
presented a code region so that IR builtins
  __builtin_{array, struct, union}_preserve_access_index
can be applied.

This patch removed the pointer type restriction to permit any
argument type as long as it is permitted by the compiler.

Differential Revision: https://reviews.llvm.org/D67883

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@372516 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 3 deletions

diff --git a/docs/LanguageExtensions.rst b/docs/LanguageExtensions.rst
index 9826c41c35..23c8778113 100644
--- a/docs/LanguageExtensions.rst
+++ b/docs/LanguageExtensions.rst
@@ -2354,13 +2354,13 @@ array subscript access and structure/union member access are relocatable
 under bpf compile-once run-everywhere framework. Debuginfo (typically
 with ``-g``) is needed, otherwise, the compiler will exit with an error.
 The return type for the intrinsic is the same as the type of the
-argument, and must be a pointer type.
+argument.
 
 **Syntax**:
 
 .. code-block:: c
 
-  PointerT __builtin_preserve_access_index(PointerT ptr)
+  type __builtin_preserve_access_index(type arg)
 
 **Example of Use**:
 
@@ -2375,7 +2375,8 @@ argument, and must be a pointer type.
     } c[4];
   };
   struct t *v = ...;
-  const void *pb =__builtin_preserve_access_index(&v->c[3].b);
+  int *pb =__builtin_preserve_access_index(&v->c[3].b);
+  __builtin_preserve_access_index(v->j);
 
 Multiprecision Arithmetic Builtins
 ----------------------------------