[riot-notifications] [RIOT-OS/RIOT] cpu/arm7_common: Make irq_*() compiler barriers (#11440)

Kaspar Schleiser notifications at github.com
Thu Apr 25 10:28:38 CEST 2019

kaspar030 commented on this pull request.

>      return retval;
 int irq_is_in(void)
     int retval;
-    __asm__ volatile(" mrs  %0, cpsr" : "=r"(retval) : /* no inputs */);
+    __asm__ volatile(" mrs  %0, cpsr" : "=r"(retval) : /* no inputs */ : "memory");

> could be transformed into:

Uff, is the compiler allowed to do this? Do you have a reference?

For local variables, that transformation wouldn't matter. This would only affect accesses to global variables (or writes through pointers).

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