RealView Compilation Tools - ARM Information Center

Compiler-specific Features
Example
void foo(void)
{
int was_masked = __disable_irq();
/* ... */
if (!was_masked)
__enable_irq();
}
Restrictions
The difference in function prototypes between the generic ARMv7 architecture and the
ARMv7 A, R, and M-profiles exists because the way that the previous IRQ state is
returned differs between the M-profile and the A and R-profiles. This means that when
you compile with --cpu=7, the compiler is unable to generate an instruction sequence
that works on all ARMv7 processors, so you must use the void __disable_irq(void);
function prototype with --cpu=7.
The following example illustrates the difference between compiling for ARMv7-M and
ARMv7-R:
/* test.c */
void DisableIrq(void)
{
__disable_irq();
}
int DisableIrq2(void)
{
return __disable_irq();
}
armcc -c --cpu=Cortex-M3 --thumb -o m3.o test.c
DisableIrq
0x00000000: b672 r. CPSID i
0x00000002: 4770 pG BX lr
DisableIrq2
0x00000004: f3ef8010 .... MRS r0,PRIMASK
0x00000008: f0000001 .... AND r0,r0,#1
0x0000000c: b672 r. CPSID i
0x0000000e: 4770 pG BX lr
armcc -c --cpu=Cortex-R4 --thumb -o r4.o test.c
DisableIrq
0x00000000: b672 r. CPSID i
0x00000002: 4770 pG BX lr
DisableIrq2
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