[Bug tree-optimization/50417] regression: memcpy with known alignment

[npl at chello dot at]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50417

npl at chello dot at changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |npl at chello dot at

--- Comment #7 from npl at chello dot at ---
This seems to affect even the most trivial cases. I ran the following code witn
arm gcc 4.8.4, 4.9.2 and 5.3.0:

#include <stdint.h>
#include <string.h>

uint32_t foo_noalign(const uint32_t *s) {
        uint32_t v;
        memcpy(&v, s, sizeof(v));
        return v;
}

uint32_t foo(const uint32_t *s) {
        uint32_t v;
        memcpy(&v, __builtin_assume_aligned(s, 4), sizeof(v));
        return v;
}

Which generates the following code:

00000000 <foo_noalign>:
   0:   e92d4007        push    {r0, r1, r2, lr}
   4:   e3a02004        mov     r2, #4
   8:   e1a01000        mov     r1, r0
   c:   e08d0002        add     r0, sp, r2
  10:   ebfffffe        bl      0 <memcpy>
  14:   e59d0004        ldr     r0, [sp, #4]
  18:   e28dd00c        add     sp, sp, #12
  1c:   e49de004        pop     {lr}            ; (ldr lr, [sp], #4)
  20:   e12fff1e        bx      lr

00000024 <foo>:
  24:   e5900000        ldr     r0, [r0]
  28:   e12fff1e        bx      lr

Thats really, really bad. clang has no problems generating the optimal code.