On Tue, 7 Jan 2020, Christophe Lyon wrote:
I've received a support request where GCC generates strd/ldrd which
require aligned memory addresses, while the user code actually
provides sub-aligned pointers.
The sample code is derived from CMSIS:
#define __SIMD32_TYPE int
#define __SIMD32(addr) (*(__SIMD32_TYPE **) & (addr))
void foo(short *pDst, int in1, int in2) {
*__SIMD32(pDst)++ = in1;
*__SIMD32(pDst)++ = in2;
}
compiled with arm-none-eabi-gcc -mcpu=cortex-m7 CMSIS.c -S -O2
generates:
foo:
strd r1, r2, [r0]
bx lr
Using -mno-unaligned-access of course makes no change, since the code
is lying to the compiler by casting short* to int*.
If the issue is as well isolated as this, can't they just edit the code?
typedef int __SIMD32_TYPE __attribute__((aligned(1)));
gets
str r1, [r0] @ unaligned
str r2, [r0, #4] @ unaligned
instead of
strd r1, r2, [r0]
--
Marc Glisse
