On Mon, 2 Aug 2010, Bingfeng Mei wrote:
> Hi,
> I ran a small test to see how the trunk/4.5 works
> with the rewritten restrict qualified pointer code. But it doesn't
> seem to work on both x86-64 and our port.
>
> tst.c:
> void foo (int * restrict a, int * restrict b,
> int * restrict c, int * restrict d)
> {
> *c = *a + 1;
> *d = *b + 1;
> }
[snip]
> foo:
> .LFB0:
> .cfi_startproc
> movl (%rdi), %eax
> addl $1, %eax
> movl %eax, (%rdx)
> movl (%rsi), %eax
> addl $1, %eax
> movl %eax, (%rcx)
> ret
>
> In the finally generated code, the second load should have
> been moved before the first store if restrict qualifiers
> are handled correctly.
>
> Am I missing something here? Thanks.
The second load is moved for me with -fschedule-insns, -frename-registers or
-fselective-scheduling2 (all of which are disabled by default on x86-64 -O2).
Without those flags, second scheduler alone cannot lift the load due to
dependency on %eax.
Hope that helps.
Alexander
