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Currently, Sparse treats 'plain' bitfields as unsigned.
However, this is this is inconsistent with how non-bitfield integers
are handled and with how GCC & clang handle bitfields.
So, teach sparse about '-funsigned-bitfields' and by default treat
these bitfields are signed, like done by GCC & clang and like done
for non-bitfield integers.
Also, avoid plain bitfields in IR related testcases.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
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The simplification of TRUNC(SHIFT(a | b, S), N) can be done by
combining the effective mask corresponding to TRUNC(_, N) with
the one corresponding to SHIFT(_, S).
This allows to also simplify signed bitfields. For example, code like:
struct s {
signed int :2;
signed int f:3;
};
int bfs(struct s s, int a)
{
s.f = a;
return s.f;
}
is now simplified into the minimal:
bfs:
trunc.3 %r4 <- (32) %arg2
sext.32 %r11 <- (3) %r4
ret.32 %r11
The simplification is done by calling simplify_mask_shift() with
the mask corresponding to TRUNC(_, N).
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
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The extraction & insertion of bitfields is made of relatively
complex combinations of SHL/LSR/AND/OR and TRUNC/ZEXT/SEXT.
Add a few testcases showing the effectiveness of their
simplification and to catch possible future regressions.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
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