When we compute excessive byte alignment get_pointer_alignment_1
may end up returning an alignment of zero due to overflow when
multiplying with BITS_PER_UNIT. This in turn causes get_object_alignment
to return a too conservative (byte) alignment.
Fixed as follows.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2015-12-04 Richard Biener <rguent...@suse.de>
PR middle-end/68636
* builtins.c (get_pointer_alignment_1): Take care of byte to
bit alignment computation overflow.
Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c (revision 231058)
+++ gcc/builtins.c (working copy)
@@ -497,6 +497,10 @@ get_pointer_alignment_1 (tree exp, unsig
{
*bitposp = ptr_misalign * BITS_PER_UNIT;
*alignp = ptr_align * BITS_PER_UNIT;
+ /* Make sure to return a sensible alignment when the multiplication
+ by BITS_PER_UNIT overflowed. */
+ if (*alignp == 0)
+ *alignp = 1u << (HOST_BITS_PER_INT - 1);
/* We cannot really tell whether this result is an approximation. */
return true;
}
