[ARM] LLVM's -arm-assume-misaligned-load-store equivalent in GCC?

[Christophe Lyon]

Hi,

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*.

However, LLVM has -arm-assume-misaligned-load-store which disables
generation of ldrd/strd in such cases:
https://reviews.llvm.org/D17015?id=48020

Would some equivalent be acceptable in GCC? I have a small patch that
seems to work.

Thanks,

Christophe