diff options
| author | Keith Packard <keithp@keithp.com> | 2016-12-17 20:58:36 -0800 |
|---|---|---|
| committer | Keith Packard <keithp@keithp.com> | 2016-12-17 21:04:33 -0800 |
| commit | 89ecc32b90565ace078c4a84d4406a4d1f86821a (patch) | |
| tree | 3b32f1d922380b3dfd25db75552a30dc84c24d41 /src/kernel/ao_pyro.c | |
| parent | f650211f9e99e1d3d0ae13ae559dd1c082f71545 (diff) | |
altos/arm: Align data so that gcc 5.4 doesn't do byte-accesses. Add -Wcast-align
Gcc 5.4.1 tracks alignment of data through assignments, so that a
uint32_t pointer which comes from byte-aligned uint8_t data:
extern uint8_t foo[];
uint32_t *q = (void *) foo;
Fetches and stores through this pointer are done bytewise. This is
slow (meh), but if q references a device register, things to bad very
quickly.
This patch works around this bug in the compiler by adding
__attribute__((aligned(4))) tags to some variables, or changing them
from uint8_t to uint32_t. Places doing this will now be caught as I've
added -Wcast-align to the compiler flags. That required adding (void
*) casts, after the relevant code was checked to make sure the
compiler could tell that the addresses were aligned.
Signed-off-by: Keith Packard <keithp@keithp.com>
Diffstat (limited to 'src/kernel/ao_pyro.c')
| -rw-r--r-- | src/kernel/ao_pyro.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/src/kernel/ao_pyro.c b/src/kernel/ao_pyro.c index b11d1080..a0881f9e 100644 --- a/src/kernel/ao_pyro.c +++ b/src/kernel/ao_pyro.c @@ -438,7 +438,7 @@ ao_pyro_show(void) if (ao_pyro_values[v].flag & AO_PYRO_8_BIT_VALUE) value = *((uint8_t *) ((char *) pyro + ao_pyro_values[v].offset)); else - value = *((int16_t *) ((char *) pyro + ao_pyro_values[v].offset)); + value = *((int16_t *) (void *) ((char *) pyro + ao_pyro_values[v].offset)); printf ("%6d ", value); } else { printf (" "); @@ -517,7 +517,7 @@ ao_pyro_set(void) } else { if (negative) ao_cmd_lex_i = -ao_cmd_lex_i; - *((int16_t *) ((char *) &pyro_tmp + ao_pyro_values[v].offset)) = ao_cmd_lex_i; + *((int16_t *) (void *) ((char *) &pyro_tmp + ao_pyro_values[v].offset)) = ao_cmd_lex_i; } } } |