Hello,
At least in GCC 4.2.1, it prints out "restrict" in gimple format so that
I can track how restrict is passed along optimizations. But it
disapprears in GCC 4.3.0
tst.c.004t.gimple produced by GCC 4.3.0
tst2 (a, b, c)
{
unsigned int i.0;
unsigned int D.1591;
V2W * D.1592;
V2W * D.1593;
vector int D.1594;
V2W * D.1595;
vector int D.1596;
vector int D.1597;
int i;
i = 0;
goto <D.1588>;
<D.1587>:;
i.0 = (unsigned int) i;
D.1591 = i.0 * 8;
D.1592 = c + D.1591;
i.0 = (unsigned int) i;
D.1591 = i.0 * 8;
D.1593 = a + D.1591;
D.1594 = *D.1593;
i.0 = (unsigned int) i;
D.1591 = i.0 * 8;
D.1595 = b + D.1591;
D.1596 = *D.1595;
D.1597 = D.1594 + D.1596;
*D.1592 = D.1597;
i = i + 1;
<D.1588>:;
if (i <= 255)
{
goto <D.1587>;
}
else
{
goto <D.1589>;
}
<D.1589>:;
}
tst.c.004t.gimple produced by GCC 4.2.1
tst2 (a, b, c)
{
unsigned int i.0;
unsigned int D.1891;
V2W * D.1892;
V2W * D.1893;
V2W * D.1894;
vector int D.1895;
V2W * D.1896;
vector int D.1897;
vector int D.1898;
int i;
i = 0;
goto <D1888>;
<D1887>:;
i.0 = (unsigned int) i;
D.1891 = i.0 * 8;
D.1892 = (V2W * restrict) D.1891;
D.1893 = D.1892 + c;
i.0 = (unsigned int) i;
D.1891 = i.0 * 8;
D.1892 = (V2W * restrict) D.1891;
D.1894 = D.1892 + a;
D.1895 = *D.1894;
i.0 = (unsigned int) i;
D.1891 = i.0 * 8;
D.1892 = (V2W * restrict) D.1891;
D.1896 = D.1892 + b;
D.1897 = *D.1896;
D.1898 = D.1895 + D.1897;
*D.1893 = D.1898;
i = i + 1;
<D1888>:;
if (i <= 255)
{
goto <D1887>;
}
else
{
goto <D1889>;
}
<D1889>:;
}
> At the RTL level, restrict ends up being transformed into a different
alias set.
Could you elaborate a little bit more? Which function/structure should I
look at? I tried to grep restrict/alias/.., no much clue. Thanks.
Bingfeng Mei
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of
Daniel Berlin
Sent: 15 April 2008 18:03
To: Bingfeng Mei
Cc: gcc@gcc.gnu.org
Subject: Re: Where is restrict keyword used in dependence analysis?
On Tue, Apr 15, 2008 at 12:01 PM, Bingfeng Mei <[EMAIL PROTECTED]>
wrote:
> Hello,
>
> I am porting to GCC 4.3.0 for our VLIW processor, and try to utilize
> improved restrict keyword support. Somehow, I find for normal data
> types, including vector types up to 8bytes, the restrict keyword
works
> just fine. But for wider vector, such as 4 32-bit word type, the
> restrict keyword doesn't work any more. For example, for the first
two
> following functions, compiler can unroll (-funroll-all-loops) loops
and
> produces good schedule, where load instructions of next iteration can
be
> moved beyond store instruction of this iteration. But for the third
> example, it is different. As suggested in .sched2 file, the compiler
can
> only resolve dependence of next load instructions after store
> instruction of this iteration is scheduled. I tried to print out
> tree-ssa files by using -fdump-tree-all. Unliked previous GCC
(4.2.1),
> the information in those files is not helpful at all.
How not?
If we don't know, we can't fix them :)
> I don't know
> where to look at now. Could someone point me some
files/functions/data
> structures by which restrict keyword is used and passed to dependence
> anaylsis part? Thanks in advance.
You mean the dependence analysis used by the scheduler?
That stuff is in sched-deps.c
At the RTL level, restrict ends up being transformed into a different
alias set.
At the tree level, restrict info is not used very much right now.
> Example code:
>
> typedef int V4W __attribute__ ((vector_size (16)));
> typedef int V2W __attribute__ ((vector_size (8)));
>
> void tst(int * restrict a, int * restrict b, int * restrict c)
> {
> int i;
> for(i = 0; i < 256; i++){
> c[i] = a[i] + b[i];
> }
> }
>
> void tst2(int * restrict a, int * restrict b, int * restrict c)
> {
> int i;
> for(i = 0; i < 256; i++){
> c[i] = a[i] + b[i];
> }
> }
>
> void tst3(V4W * restrict a, V4W * restrict b, V4W * restrict c)
> {
> int i;
> for(i = 0; i < 256; i++){
> c[i] = a[i] + b[i];
> }
> }
>
>
>
