The following is an attempt to fix PR71598 where C (and C++?) have
an implementation-defined compatible integer type for each enum
and the TBAA rules mandate that accesses using a compatible type
are allowed.
The fix is applied to all C family frontends and the LTO frontend
but not Fortran, Ada or other languages.
Bootstrap & regtest running on x86_64-unknown-linux-gnu.
I've tried to cover most cases even those with -fshort-enums.
OK for trunk?
It's probably a regression to some ancient GCC that didn't
perform TBAA and given it's wrong-code a backport is probably
mandated - do you agree? (after a while with no reported issues,
of course)
Thanks,
Richard.
2019-03-15 Richard Biener <rguent...@suse.de>
PR c/71598
* gimple.c: Include langhooks.h.
(gimple_get_alias_set): Treat enumeral types as the underlying
integer type.
c-family/
* c-common.c (c_common_get_alias_set): Treat enumeral types
as the underlying integer type.
* c-c++-common/torture/pr71598-1.c: New testcase.
* c-c++-common/torture/pr71598-2.c: Likewise.
Index: gcc/gimple.c
===================================================================
--- gcc/gimple.c (revision 269704)
+++ gcc/gimple.c (working copy)
@@ -44,6 +44,7 @@ along with GCC; see the file COPYING3.
#include "stringpool.h"
#include "attribs.h"
#include "asan.h"
+#include "langhooks.h"
/* All the tuples have their operand vector (if present) at the very bottom
@@ -2587,6 +2588,16 @@ gimple_get_alias_set (tree t)
return get_alias_set (t1);
}
+ /* Allow aliasing between enumeral types and the underlying
+ integer type. This is required for C since those are
+ compatible types. */
+ else if (TREE_CODE (t) == ENUMERAL_TYPE)
+ {
+ tree t1 = lang_hooks.types.type_for_size (tree_to_uhwi (TYPE_SIZE (t)),
+ false /* short-cut above */);
+ return get_alias_set (t1);
+ }
+
return -1;
}
Index: gcc/c-family/c-common.c
===================================================================
--- gcc/c-family/c-common.c (revision 269704)
+++ gcc/c-family/c-common.c (working copy)
@@ -3681,6 +3681,15 @@ c_common_get_alias_set (tree t)
return get_alias_set (t1);
}
+ /* Allow aliasing between enumeral types and the underlying
+ integer type. This is required since those are compatible types. */
+ else if (TREE_CODE (t) == ENUMERAL_TYPE)
+ {
+ tree t1 = c_common_type_for_size (tree_to_uhwi (TYPE_SIZE (t)),
+ false /* short-cut above */);
+ return get_alias_set (t1);
+ }
+
return -1;
}
Index: gcc/testsuite/c-c++-common/torture/pr71598-1.c
===================================================================
--- gcc/testsuite/c-c++-common/torture/pr71598-1.c (nonexistent)
+++ gcc/testsuite/c-c++-common/torture/pr71598-1.c (working copy)
@@ -0,0 +1,21 @@
+/* { dg-do run } */
+/* { dg-additional-options "-fno-short-enums" } */
+
+enum e1 { c1 };
+
+__attribute__((noinline,noclone))
+int f(enum e1 *p, unsigned *q)
+{
+ *p = c1;
+ *q = 2;
+ return *p;
+}
+
+int main()
+{
+ unsigned x;
+
+ if (f((enum e1 *)&x, &x) != 2)
+ __builtin_abort();
+ return 0;
+}
Index: gcc/testsuite/c-c++-common/torture/pr71598-2.c
===================================================================
--- gcc/testsuite/c-c++-common/torture/pr71598-2.c (nonexistent)
+++ gcc/testsuite/c-c++-common/torture/pr71598-2.c (working copy)
@@ -0,0 +1,47 @@
+/* { dg-do run } */
+/* { dg-additional-options "-fshort-enums" } */
+
+enum e1 { c1 = -__INT_MAX__ };
+
+__attribute__((noinline,noclone))
+int f(enum e1 *p, signed int *q)
+{
+ *p = c1;
+ *q = 2;
+ return *p;
+}
+
+enum e2 { c2 = __SHRT_MAX__ + 1};
+
+__attribute__((noinline,noclone))
+int g(enum e2 *p, unsigned short *q)
+{
+ *p = c2;
+ *q = 2;
+ return *p;
+}
+
+enum e3 { c3 = __SCHAR_MAX__ };
+
+__attribute__((noinline,noclone))
+int h(enum e3 *p, unsigned char *q)
+{
+ *p = c3;
+ *q = 2;
+ return *p;
+}
+
+int main()
+{
+ signed x;
+ unsigned short y;
+ unsigned char z;
+
+ if (f((enum e1 *)&x, &x) != 2)
+ __builtin_abort();
+ if (g((enum e2 *)&y, &y) != 2)
+ __builtin_abort();
+ if (h((enum e3 *)&z, &z) != 2)
+ __builtin_abort();
+ return 0;
+}
