http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50749
--- Comment #14 from Oleg Endo <olegendo at gcc dot gnu.org> ---
Just wanted to clarify the reason why the examples in the description have
'-fno-ivopts', as it caused some confusion on the mailing list:
int test_0 (char* p, int c)
{
int r = 0;
r += *p++;
r += *p++;
r += *p++;
return r;
}
compiled with -m4 -O2:
mov.b @(1,r4),r0
mov.b @r4,r1
add r0,r1
mov.b @(2,r4),r0
rts
add r1,r0
compiled with -m4 -Os:
mov.b @(1,r4),r0
mov.b @r4,r2
add r0,r2
mov.b @(2,r4),r0
add r0,r2
rts
mov r2,r0
As seen above, the memory accesses are turned into reg+disp addressing,
although on SH using post-inc addressing would be cheaper (as it is also
reported 'sh_address_cost').
Turning off ivopts leaves the post-inc addressing and points out the original
problem of this PR. I believe that the proper fix for this would be having PR
56590 fixed.
