------- Comment #17 from ebotcazou at gcc dot gnu dot org 2008-01-08 17:10
-------
Michael, any reason for being so scrupulous and not forcing the mode?
Index: expr.c
===================================================================
--- expr.c (revision 131326)
+++ expr.c (working copy)
@@ -2061,6 +2061,7 @@ copy_blkmode_from_reg (rtx tgtblk, rtx s
rtx src = NULL, dst = NULL;
unsigned HOST_WIDE_INT bitsize = MIN (TYPE_ALIGN (type), BITS_PER_WORD);
unsigned HOST_WIDE_INT bitpos, xbitpos, padding_correction = 0;
+ enum machine_mode copy_mode;
if (tgtblk == 0)
{
@@ -2094,11 +2095,19 @@ copy_blkmode_from_reg (rtx tgtblk, rtx s
padding_correction
= (BITS_PER_WORD - ((bytes % UNITS_PER_WORD) * BITS_PER_UNIT));
- /* Copy the structure BITSIZE bites at a time.
+ /* Copy the structure BITSIZE bits at a time. If the target lives in
+ memory, take care of not reading/writing past its end by selecting
+ a copy mode suited to BITSIZE. This should always be possible given
+ how it is computed.
We could probably emit more efficient code for machines which do not use
strict alignment, but it doesn't seem worth the effort at the current
time. */
+
+ if (!MEM_P (tgtblk)
+ || ((copy_mode = mode_for_size (bitsize, MODE_INT, 1)) == BLKmode))
+ copy_mode = word_mode;
+
for (bitpos = 0, xbitpos = padding_correction;
bitpos < bytes * BITS_PER_UNIT;
bitpos += bitsize, xbitpos += bitsize)
@@ -2117,11 +2126,11 @@ copy_blkmode_from_reg (rtx tgtblk, rtx s
dst = operand_subword (tgtblk, bitpos / BITS_PER_WORD, 1, BLKmode);
/* Use xbitpos for the source extraction (right justified) and
- xbitpos for the destination store (left justified). */
- store_bit_field (dst, bitsize, bitpos % BITS_PER_WORD, word_mode,
+ bitpos for the destination store (left justified). */
+ store_bit_field (dst, bitsize, bitpos % BITS_PER_WORD, copy_mode,
extract_bit_field (src, bitsize,
xbitpos % BITS_PER_WORD, 1,
- NULL_RTX, word_mode, word_mode));
+ NULL_RTX, copy_mode, copy_mode));
}
return tgtblk;
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31309
