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bitfields: fix PCC layout

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Fixes some corner cases in PCC layout.  Testcases coming
up.
This commit is contained in:
Michael Matz 2016-11-11 17:33:31 +01:00
parent bd69bce20f
commit ed680da951
1 changed files with 28 additions and 23 deletions
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51
tccgen.c
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@ -3267,6 +3267,7 @@ static void struct_add_offset (Sym *s, int offset)
static void struct_layout(CType *type, AttributeDef *ad)
{
int align, maxalign, offset, c, bit_pos, bt, prevbt;
int pcc = !tcc_state->ms_bitfields;
Sym *f;
if (ad->a.aligned)
maxalign = ad->a.aligned;
@ -3280,13 +3281,12 @@ static void struct_layout(CType *type, AttributeDef *ad)
int extra_bytes = 0;
int typealign, bit_size;
int size = type_size(&f->type, &typealign);
int pcc = !tcc_state->ms_bitfields;
if (f->type.t & VT_BITFIELD) {
bit_size = (f->type.t >> (VT_STRUCT_SHIFT + 6)) & 0x3f;
/* without ms-bitfields, allocate the
* minimum number of bytes necessary,
* adding single bytes as needed */
if (!tcc_state->ms_bitfields) {
if (0 && !tcc_state->ms_bitfields) {
if (bit_pos == 0)
/* minimum bytes for new bitfield */
size = (bit_size + 7) / 8;
@ -3311,55 +3311,59 @@ static void struct_layout(CType *type, AttributeDef *ad)
} else {
align = typealign;
}
/*if (extra_bytes) c += extra_bytes;
else*/ if (bit_size < 0) {
int addbytes = pcc ? (bit_pos + 7) >> 3 : 0;
if (extra_bytes) c += extra_bytes;
else if (bit_size < 0) {
prevbt = VT_STRUCT;
if (type->ref->type.t == TOK_STRUCT) {
int addbytes = pcc ? (bit_pos + 7) >> 3 : 0;
c = (c + addbytes + align - 1) & -align;
offset = c;
if (size > 0)
c += size;
} else {
union_tail:
offset = 0;
if (addbytes > c)
c = addbytes;
if (size > c)
c = size;
}
if (align > maxalign)
maxalign = align;
bit_pos = 0;
prevbt = VT_STRUCT;
} else if (type->ref->type.t != TOK_STRUCT) {
if (pcc)
size = (bit_size + 7) >> 3;
f->type.t = (f->type.t & ~(0x3f << VT_STRUCT_SHIFT))
| (0 << VT_STRUCT_SHIFT);
goto union_tail;
} else {
/* A bit-field. Layout is more complicated. There are two
options TCC implements: PCC compatible and MS compatible
(PCC compatible is what GCC uses for almost all targets). */
if (!bit_pos) {
if (type->ref->type.t == TOK_STRUCT) {
/* Don't align c here. That's only to be done
in certain cases. */
offset = c;
} else {
offset = 0;
}
}
if (pcc) {
/* In PCC layout a non-packed bit-field is placed adjacent
to the preceding bit-fields, except if it would overflow
its container (depending on base type) or it's a zero-width
bit-field. Packed non-zero-width bit-fields always are
placed adjacent. */
if ((typealign != 1 &&
bit_pos + bit_size > size * 8) ||
bit_size == 0) {
int ofs = (c * 8 + bit_pos) % (typealign * 8);
int ofs2 = ofs + bit_size + (typealign * 8) - 1;
/*if ((typealign != 1 &&
//bit_pos + bit_size > size * 8) ||
(((c + ((bit_pos + 7) >> 3) + typealign - 1) & -typealign)
!= ((c + ((bit_pos + bit_size + 7) >> 3) + typealign - 1) & -typealign))) ||
bit_size == 0 ||
(bit_pos + bit_size > size * 8)
) {*/
if (bit_size == 0 ||
(typealign != 1 && (ofs2 / (typealign * 8)) > ((size*8)/(typealign*8)))) {
c = (c + ((bit_pos + 7) >> 3) + typealign - 1) & -typealign;
offset = c;
bit_pos = 0;
}
offset = c;
/* In PCC layout named bit-fields influence the alignment
of the containing struct using the base types alignment,
except for packed fields or zero-width fields. */
if (bit_size > 0) {
if (!(f->v & SYM_FIRST_ANOM)) {
if (align > maxalign)
maxalign = align;
if (typealign > maxalign)
@ -3444,7 +3448,8 @@ static void struct_layout(CType *type, AttributeDef *ad)
f->r = 0;
}
/* store size and alignment */
type->ref->c = (c + ((bit_pos + 7) >> 3) + maxalign - 1) & -maxalign;
type->ref->c = (c + (pcc ? (bit_pos + 7) >> 3 : 0)
+ maxalign - 1) & -maxalign;
type->ref->r = maxalign;
}