diff options
| author | Keith Packard <keithp@keithp.com> | 2016-12-17 20:58:36 -0800 |
|---|---|---|
| committer | Bdale Garbee <bdale@gag.com> | 2017-01-25 12:21:43 -0700 |
| commit | fe25510fc23031f1a3c1b42edd37067d1989a9f6 (patch) | |
| tree | 3cdc98d2c3d1c8d9bd95045771be7d15226d246b /src/stm/ao_usb_stm.c | |
| parent | 4163d88ed36ce8863218366f1fb504f7061a4ca5 (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/stm/ao_usb_stm.c')
| -rw-r--r-- | src/stm/ao_usb_stm.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/src/stm/ao_usb_stm.c b/src/stm/ao_usb_stm.c index f2b8ea94..9d72844e 100644 --- a/src/stm/ao_usb_stm.c +++ b/src/stm/ao_usb_stm.c @@ -139,7 +139,7 @@ static inline uint32_t set_toggle(uint32_t current_value, static inline uint32_t *ao_usb_packet_buffer_addr(uint16_t sram_addr) { - return (uint32_t *) (stm_usb_sram + 2 * sram_addr); + return (uint32_t *) (((void *) ((uint8_t *) stm_usb_sram + 2 * sram_addr))); } static inline uint32_t ao_usb_epr_stat_rx(uint32_t epr) { |