[CLANG][BPF] change __builtin_preserve_access_index() signature

The clang intrinsic __builtin_preserve_access_index() currently
has signature:
  const void * __builtin_preserve_access_index(const void * ptr)

This may cause compiler warning when:
  - parameter type is "volatile void *" or "const volatile void *", or
  - the assign-to type of the intrinsic does not have "const" qualifier.
Further, this signature does not allow dereference of the
builtin result pointer as it is a "const void *" type, which
adds extra step for the user to do type casting.

Let us change the signature to:
  PointerT __builtin_preserve_access_index(PointerT ptr)
such that the result and argument types are the same.
With this, directly dereferencing the builtin return value
becomes possible.

Differential Revision: https://reviews.llvm.org/D67734

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@372294 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 22 insertions, 4 deletions

diff --git a/test/Sema/builtin-preserve-access-index.c b/test/Sema/builtin-preserve-access-index.c
index c10ceb5145..71da8457fa 100644
--- a/test/Sema/builtin-preserve-access-index.c
+++ b/test/Sema/builtin-preserve-access-index.c
@@ -4,10 +4,28 @@ const void *invalid1(const int *arg) {
   return __builtin_preserve_access_index(&arg[1], 1); // expected-error {{too many arguments to function call, expected 1, have 2}}
 }
 
-void *invalid2(const int *arg) {
-  return __builtin_preserve_access_index(&arg[1]); // expected-warning {{returning 'const void *' from a function with result type 'void *' discards qualifiers}}
+const void *invalid2(const int *arg) {
+  return __builtin_preserve_access_index(1); // expected-error {{__builtin_preserve_access_index argument must a pointer type instead of 'int'}}
 }
 
-const void *invalid3(const int *arg) {
-  return __builtin_preserve_access_index(1); // expected-warning {{incompatible integer to pointer conversion passing 'int' to parameter of type 'const void *'}}
+void *invalid3(const int *arg) {
+  return __builtin_preserve_access_index(&arg[1]); // expected-warning {{returning 'const int *' from a function with result type 'void *' discards qualifiers}}
+}
+
+const void *invalid4(volatile const int *arg) {
+  return __builtin_preserve_access_index(arg); // expected-warning {{returning 'const volatile int *' from a function with result type 'const void *' discards qualifiers}}
+}
+
+int *valid5(int *arg) {
+  return __builtin_preserve_access_index(arg);
+}
+
+int valid6(const volatile int *arg) {
+  return *__builtin_preserve_access_index(arg);
+}
+
+struct s { int a; int b; };
+
+int valid7(struct s *arg) {
+  return *__builtin_preserve_access_index(&arg->b);
 }