This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[PATCH] Fix PR middle-end/26565, memcpy alignment issue
- From: Richard Guenther <rguenther at suse dot de>
- To: gcc-patches at gcc dot gnu dot org
- Date: Mon, 6 Mar 2006 15:52:10 +0100 (CET)
- Subject: [PATCH] Fix PR middle-end/26565, memcpy alignment issue
This patch fixes PR26565, emitting unaligned stores for
void *memcpy(void *dest, const void *src, __SIZE_TYPE__ n);
struct timeval {
long tv_sec;
};
struct outdata {
char seq;
struct timeval tv __attribute__((packed));
};
void send_probe(struct outdata *outdata, struct timeval *tp)
{
memcpy(&outdata->tv, tp, sizeof outdata->tv);
}
on STRICT_ALIGNMENT targets. builtins.c:get_pointer_alignment is simply
overly optimistic about the alignment it can infer. Fixed by looking
through component references and taking into account their DECL_ALIGN.
The only way to workaround the bug I found is to use (char*)outdata+1 for
the destination parameter. A direct assignment outdata->tv = *tp also
works as expected.
Boostrapped and regtested on ia64-unknown-linux-gnu.
Ok for mainline, 4.1 and 4.0?
Thanks,
Richard.
:ADDPATCH middle-end:
2006-03-06 Richard Guenther <rguenther@suse.de>
PR middle-end/26565
* builtins.c (get_pointer_alignment): Handle component
references for field alignment.
Index: builtins.c
===================================================================
*** builtins.c (revision 111638)
--- builtins.c (working copy)
*************** get_pointer_alignment (tree exp, unsigne
*** 275,289 ****
case ADDR_EXPR:
/* See what we are pointing at and look at its alignment. */
exp = TREE_OPERAND (exp, 0);
if (TREE_CODE (exp) == FUNCTION_DECL)
! align = FUNCTION_BOUNDARY;
else if (DECL_P (exp))
! align = DECL_ALIGN (exp);
#ifdef CONSTANT_ALIGNMENT
else if (CONSTANT_CLASS_P (exp))
! align = CONSTANT_ALIGNMENT (exp, align);
#endif
! return MIN (align, max_align);
default:
return align;
--- 275,295 ----
case ADDR_EXPR:
/* See what we are pointing at and look at its alignment. */
exp = TREE_OPERAND (exp, 0);
+ while (handled_component_p (exp))
+ {
+ if (TREE_CODE (exp) == COMPONENT_REF)
+ align = MIN (align, DECL_ALIGN (TREE_OPERAND (exp, 1)));
+ exp = TREE_OPERAND (exp, 0);
+ }
if (TREE_CODE (exp) == FUNCTION_DECL)
! align = MIN (align, FUNCTION_BOUNDARY);
else if (DECL_P (exp))
! align = MIN (align, DECL_ALIGN (exp));
#ifdef CONSTANT_ALIGNMENT
else if (CONSTANT_CLASS_P (exp))
! align = MIN (align, (unsigned)CONSTANT_ALIGNMENT (exp, align));
#endif
! return align;
default:
return align;