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Implement gcc bitfield algorithm; add -mms-bitfields

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This commit is contained in:
David Mertens
2016-11-22 16:33:12 -05:00
parent 3c68a8c6c0
commit d2e2f42382
6 changed files with 44 additions and 7 deletions
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30
tccgen.c
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@ -3154,7 +3154,7 @@ static void parse_attribute(AttributeDef *ad)
/* enum/struct/union declaration. u is either VT_ENUM or VT_STRUCT */
static void struct_decl(CType *type, AttributeDef *ad, int u)
{
int a, v, size, align, maxalign, c, offset, flexible;
int a, v, size, align, maxalign, c, offset, flexible, extra_bytes;
int bit_size, bit_pos, bsize, bt, lbit_pos, prevbt;
Sym *s, *ss, *ass, **ps;
AttributeDef ad1;
@ -3235,6 +3235,7 @@ static void struct_decl(CType *type, AttributeDef *ad, int u)
while (tok != '}') {
parse_btype(&btype, &ad1);
while (1) {
extra_bytes = 0;
if (flexible)
tcc_error("flexible array member '%s' not at the end of struct",
get_tok_str(v, NULL));
@ -3310,9 +3311,9 @@ static void struct_decl(CType *type, AttributeDef *ad, int u)
/* zero size: means to pad */
bit_pos = 0;
} else {
/* we do not have enough room ?
did the type change?
is it a union? */
/* if type change, union, or will overrun
* allignment slot, start at a newly
* alligned slot */
if ((bit_pos + bit_size) > bsize ||
bt != prevbt || a == TOK_UNION)
bit_pos = 0;
@ -3322,15 +3323,30 @@ static void struct_decl(CType *type, AttributeDef *ad, int u)
(bit_pos << VT_STRUCT_SHIFT) |
(bit_size << (VT_STRUCT_SHIFT + 6));
bit_pos += bit_size;
/* without ms-bitfields, allocate the
* minimum number of bytes necessary,
* adding single bytes as needed */
if (!tcc_state->ms_bitfields) {
if (lbit_pos == 0)
/* minimum bytes for new bitfield */
size = (bit_size + 7) / 8;
else {
/* enough spare bits already allocated? */
bit_size = (lbit_pos - 1) % 8 + 1 + bit_size;
if (bit_size > 8) /* doesn't fit */
extra_bytes = (bit_size - 1) / 8;
}
}
}
prevbt = bt;
} else {
bit_pos = 0;
}
if (v != 0 || (type1.t & VT_BTYPE) == VT_STRUCT) {
/* add new memory data only if starting
bit field */
if (lbit_pos == 0) {
/* add new memory data only if starting bit
field or adding bytes to existing bit field */
if (extra_bytes) c += extra_bytes;
else if (lbit_pos == 0) {
if (a == TOK_STRUCT) {
c = (c + align - 1) & -align;
offset = c;