Stelian Pop <stel...@popies.net> writes: > On Wed, Jun 03, 2009 at 07:49:29PM +0200, Stelian Pop wrote: > >> I'm doing a port of gcc 4.3.3 on a custom architecture and I'm having trouble >> when initializing the bit fields of a structure. > > Ok, after further analysis, it looks like a genuine bug in gcc, > in store_bit_field_1(): when a field is bigger than a word, the > rvalue is splitted in several words, after being placed in a > smallest_mode_for_size() operand. > > But the logic for adressing the words of this operand is buggy > in the WORDS_BIG_ENDIAN case, the most signficant words being > used instead of the least significant ones. > > The following patch corrects this, and makes the > gcc.c-torture/execute/991118-1.c testcase work correctly on my platform. > > Stelian. > > diff --git a/gcc/expmed.c b/gcc/expmed.c > index dc61de7..03c60a8 100644 > --- a/gcc/expmed.c > +++ b/gcc/expmed.c > @@ -582,7 +582,10 @@ store_bit_field_1 (rtx str_rtx, unsigned HOST_WIDE_INT > bitsize, > { > /* If I is 0, use the low-order word in both field and target; > if I is 1, use the next to lowest word; and so on. */ > - unsigned int wordnum = (backwards ? nwords - i - 1 : i); > + unsigned int wordnum = (backwards > + ? GET_MODE_SIZE(fieldmode) / UNITS_PER_WORD > + - i - 1 > + : i); > unsigned int bit_offset = (backwards > ? MAX ((int) bitsize - ((int) i + 1) > * BITS_PER_WORD,
Your patch looks correct. However, it makes me wonder how the test case passes on existing big-endian platforms, such as the PowerPC. Can you explain how that works? Ian