electronics
/
libopencm3
9
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Cortex-M defines : fix potential issue where PRIMASK and FAULTMASK operations could be optimized out by gcc. 

This adds the "volatile" keyword to all the inline assembly. gcc docs say "You can prevent an asm instruction from being deleted by writing the keyword volatile after the asm.". Testing (see comments of github issue #475) shows that indeed gcc can remove some inline asm, in at least this situation:
-multiple calls to cm_is_masked_interrupts() in the same scope/context
- -Os or -O2 optimization
This is problem because the value of PRIMASK could change between two calls to cm_is_masked_interrupts().
Adding the volatile keyword fixes this, and probably costs less than adding a full barrier (like adding "memory" to the clobber list).
This commit is contained in:
fenugrec 2016-01-10 11:13:25 -05:00
parent 1cca117e58
commit ad5ec6af08
1 changed files with 6 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
include/libopencm3/cm3/cortex.h
View File

@ -43,7 +43,7 @@
*/
static inline void cm_enable_interrupts(void)
{
__asm__("CPSIE I\n");
__asm__ volatile ("CPSIE I\n");
}
/*---------------------------------------------------------------------------*/
@ -53,7 +53,7 @@ static inline void cm_enable_interrupts(void)
*/
static inline void cm_disable_interrupts(void)
{
__asm__("CPSID I\n");
__asm__ volatile ("CPSID I\n");
}
/*---------------------------------------------------------------------------*/
@ -63,7 +63,7 @@ static inline void cm_disable_interrupts(void)
*/
static inline void cm_enable_faults(void)
{
__asm__("CPSIE F\n");
__asm__ volatile ("CPSIE F\n");
}
/*---------------------------------------------------------------------------*/
@ -73,7 +73,7 @@ static inline void cm_enable_faults(void)
*/
static inline void cm_disable_faults(void)
{
__asm__("CPSID F\n");
__asm__ volatile ("CPSID F\n");
}
/*---------------------------------------------------------------------------*/
@ -87,7 +87,7 @@ __attribute__((always_inline))
static inline bool cm_is_masked_interrupts(void)
{
register uint32_t result;
__asm__ ("MRS %0, PRIMASK" : "=r" (result));
__asm__ volatile ("MRS %0, PRIMASK" : "=r" (result));
return result;
}
@ -102,7 +102,7 @@ __attribute__((always_inline))
static inline bool cm_is_masked_faults(void)
{
register uint32_t result;
__asm__ ("MRS %0, FAULTMASK" : "=r" (result));
__asm__ volatile ("MRS %0, FAULTMASK" : "=r" (result));
return result;
}