From fe25510fc23031f1a3c1b42edd37067d1989a9f6 Mon Sep 17 00:00:00 2001 From: Keith Packard Date: Sat, 17 Dec 2016 20:58:36 -0800 Subject: 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 --- src/kernel/ao_task.h | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'src/kernel/ao_task.h') diff --git a/src/kernel/ao_task.h b/src/kernel/ao_task.h index f1dbd654..30b018ff 100644 --- a/src/kernel/ao_task.h +++ b/src/kernel/ao_task.h @@ -26,6 +26,17 @@ #define HAS_TASK_INFO 1 #endif +/* arm stacks must be 32-bit aligned */ +#ifdef __arm__ +#define AO_STACK_ALIGNMENT __attribute__ ((aligned(4))) +#endif +#ifdef SDCC +#define AO_STACK_ALIGNMENT +#endif +#ifdef __AVR__ +#define AO_STACK_ALIGNMENT +#endif + /* An AltOS task */ struct ao_task { __xdata void *wchan; /* current wait channel (NULL if running) */ @@ -37,7 +48,7 @@ struct ao_task { struct ao_list queue; struct ao_list alarm_queue; #endif - uint8_t stack[AO_STACK_SIZE]; /* saved stack */ + uint8_t stack[AO_STACK_SIZE] AO_STACK_ALIGNMENT; /* saved stack */ #if HAS_SAMPLE_PROFILE uint32_t ticks; uint32_t yields; -- cgit v1.2.3