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bitfields: promote to signed int

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For integer promotion with for example arithmetics or
expr_cond (x ? y : z), integral types need to be promoted
to signed if they fit.

According to latest standards, this also applies to bit-field
types taking into account their specific width.

In tcc, VT_BITFIELD set means width < original type width
Field-widths between 33 and 63 are promoted to signed long long
accordingly.

    struct { unsigned long long ullb:35; } s = { 1 };
    #define X (s.ullb - 2)

    int main (void)
    {
        long long Y = X;
        printf("%d %016llx %016llx\n", X < 0, -X, -Y);
        return 0;
    }

Results:
    GCC 4.7 : 0 0000000000000001 FFFFFFF800000001
    MSVC    : 1 0000000000000001 0000000000000001
    TCC     : 1 0000000000000001 0000000000000001

Also, gcc would promote long long bitfields of size < 32
to int as well.  Example:

    struct { unsigned long long x:20; } t = { 123 };
    /* with gcc: */ printf("%d %d\n", t.x, 456);
    /* with tcc: */ printf("%lld %d\n", t.x, 456);
This commit is contained in:
grischka 2017-05-09 18:36:24 +02:00
parent d242706f3b
commit 1ed20a01c9
3 changed files with 126 additions and 9 deletions
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18
tccgen.c
View File

@ -2086,23 +2086,23 @@ redo:
goto std_op; goto std_op;
} else if (op == TOK_SHR || op == TOK_SAR || op == TOK_SHL) { } else if (op == TOK_SHR || op == TOK_SAR || op == TOK_SHL) {
t = bt1 == VT_LLONG ? VT_LLONG : VT_INT; t = bt1 == VT_LLONG ? VT_LLONG : VT_INT;
if ((t1 & (VT_BTYPE | VT_UNSIGNED)) == (t | VT_UNSIGNED)) if ((t1 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == (t | VT_UNSIGNED))
t |= VT_UNSIGNED; t |= VT_UNSIGNED;
goto std_op; goto std_op;
} else if (bt1 == VT_LLONG || bt2 == VT_LLONG) { } else if (bt1 == VT_LLONG || bt2 == VT_LLONG) {
/* cast to biggest op */ /* cast to biggest op */
t = VT_LLONG; t = VT_LLONG;
/* convert to unsigned if it does not fit in a long long */ /* convert to unsigned if it does not fit in a long long */
if ((t1 & (VT_BTYPE | VT_UNSIGNED)) == (VT_LLONG | VT_UNSIGNED) || if ((t1 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == (VT_LLONG | VT_UNSIGNED) ||
(t2 & (VT_BTYPE | VT_UNSIGNED)) == (VT_LLONG | VT_UNSIGNED)) (t2 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == (VT_LLONG | VT_UNSIGNED))
t |= VT_UNSIGNED; t |= VT_UNSIGNED;
goto std_op; goto std_op;
} else { } else {
/* integer operations */ /* integer operations */
t = VT_INT; t = VT_INT;
/* convert to unsigned if it does not fit in an integer */ /* convert to unsigned if it does not fit in an integer */
if ((t1 & (VT_BTYPE | VT_UNSIGNED)) == (VT_INT | VT_UNSIGNED) || if ((t1 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == (VT_INT | VT_UNSIGNED) ||
(t2 & (VT_BTYPE | VT_UNSIGNED)) == (VT_INT | VT_UNSIGNED)) (t2 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == (VT_INT | VT_UNSIGNED))
t |= VT_UNSIGNED; t |= VT_UNSIGNED;
std_op: std_op:
/* XXX: currently, some unsigned operations are explicit, so /* XXX: currently, some unsigned operations are explicit, so
@ -5198,8 +5198,8 @@ static void expr_cond(void)
/* cast to biggest op */ /* cast to biggest op */
type.t = VT_LLONG; type.t = VT_LLONG;
/* convert to unsigned if it does not fit in a long long */ /* convert to unsigned if it does not fit in a long long */
if ((t1 & (VT_BTYPE | VT_UNSIGNED)) == (VT_LLONG | VT_UNSIGNED) || if ((t1 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == (VT_LLONG | VT_UNSIGNED) ||
(t2 & (VT_BTYPE | VT_UNSIGNED)) == (VT_LLONG | VT_UNSIGNED)) (t2 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == (VT_LLONG | VT_UNSIGNED))
type.t |= VT_UNSIGNED; type.t |= VT_UNSIGNED;
} else if (bt1 == VT_PTR || bt2 == VT_PTR) { } else if (bt1 == VT_PTR || bt2 == VT_PTR) {
/* If one is a null ptr constant the result type /* If one is a null ptr constant the result type
@ -5225,8 +5225,8 @@ static void expr_cond(void)
/* integer operations */ /* integer operations */
type.t = VT_INT; type.t = VT_INT;
/* convert to unsigned if it does not fit in an integer */ /* convert to unsigned if it does not fit in an integer */
if ((t1 & (VT_BTYPE | VT_UNSIGNED)) == (VT_INT | VT_UNSIGNED) || if ((t1 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == (VT_INT | VT_UNSIGNED) ||
(t2 & (VT_BTYPE | VT_UNSIGNED)) == (VT_INT | VT_UNSIGNED)) (t2 & (VT_BTYPE | VT_UNSIGNED | VT_BITFIELD)) == (VT_INT | VT_UNSIGNED))
type.t |= VT_UNSIGNED; type.t |= VT_UNSIGNED;
} }
/* keep structs lvalue by transforming `(expr ? a : b)` to `*(expr ? &a : &b)` so /* keep structs lvalue by transforming `(expr ? a : b)` to `*(expr ? &a : &b)` so

71
tests/tests2/93_integer_promotion.c Normal file
View File

@ -0,0 +1,71 @@
/* integer promotion */
int printf(const char*, ...);
#define promote(s) printf(" %ssigned : %s\n", (s) - 100 < 0 ? " " : "un", #s);
int main (void)
{
struct {
unsigned ub:3;
unsigned u:32;
unsigned long long ullb:35;
unsigned long long ull:64;
unsigned char c;
} s = { 1, 1, 1 };
promote(s.ub);
promote(s.u);
promote(s.ullb);
promote(s.ull);
promote(s.c);
printf("\n");
promote((1 ? s.ub : 1));
promote((1 ? s.u : 1));
promote((1 ? s.ullb : 1));
promote((1 ? s.ull : 1));
promote((1 ? s.c : 1));
printf("\n");
promote(s.ub << 1);
promote(s.u << 1);
promote(s.ullb << 1);
promote(s.ull << 1);
promote(s.c << 1);
printf("\n");
promote(+s.ub);
promote(+s.u);
promote(+s.ullb);
promote(+s.ull);
promote(+s.c);
printf("\n");
promote(-s.ub);
promote(-s.u);
promote(-s.ullb);
promote(-s.ull);
promote(-s.c);
printf("\n");
promote(~s.ub);
promote(~s.u);
promote(~s.ullb);
promote(~s.ull);
promote(~s.c);
printf("\n");
promote(!s.ub);
promote(!s.u);
promote(!s.ullb);
promote(!s.ull);
promote(!s.c);
printf("\n");
promote(+(unsigned)s.ub);
promote(-(unsigned)s.ub);
promote(~(unsigned)s.ub);
promote(!(unsigned)s.ub);
return 0;
}

46
tests/tests2/93_integer_promotion.expect Normal file
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@ -0,0 +1,46 @@
signed : s.ub
unsigned : s.u
signed : s.ullb
unsigned : s.ull
signed : s.c
signed : (1 ? s.ub : 1)
unsigned : (1 ? s.u : 1)
signed : (1 ? s.ullb : 1)
unsigned : (1 ? s.ull : 1)
signed : (1 ? s.c : 1)
signed : s.ub << 1
unsigned : s.u << 1
signed : s.ullb << 1
unsigned : s.ull << 1
signed : s.c << 1
signed : +s.ub
unsigned : +s.u
signed : +s.ullb
unsigned : +s.ull
signed : +s.c
signed : -s.ub
unsigned : -s.u
signed : -s.ullb
unsigned : -s.ull
signed : -s.c
signed : ~s.ub
unsigned : ~s.u
signed : ~s.ullb
unsigned : ~s.ull
signed : ~s.c
signed : !s.ub
signed : !s.u
signed : !s.ullb
signed : !s.ull
signed : !s.c
unsigned : +(unsigned)s.ub
unsigned : -(unsigned)s.ub
unsigned : ~(unsigned)s.ub
signed : !(unsigned)s.ub