Hi Richard,
2010/4/14, Richard Guenther <richard.guent...@gmail.com>:
> On Wed, Apr 14, 2010 at 8:48 AM, roy rosen <roy.1ro...@gmail.com> wrote:
> > Hi All,
> >
> > I have implemented some vectorization features in my gcc port.
> >
> > In the generated code for this function I can see a scheduling problem:
> >
> > int xxx(int* __restrict__ a, int* __restrict__ b)
> > {
> > int __restrict__ i;
> > for (i = 0; i < 8; i++)
> > {
> > a[i] = b[i];
> > }
> > return 0;
> > }
> >
> > from asmcons:
> >
> > (insn 17 14 18 3 a.c:15 (set (reg:V4HI 105)
> > (mem:V4HI (reg/v/f:SI 100 [ b ]) [2 S8 A64])) 115 {*movv4hi_load}
> > (nil))
> >
> > (insn 18 17 19 3 a.c:15 (set (mem:V4HI (reg/v/f:SI 99 [ a ]) [2 S8 A64])
> > (reg:V4HI 105)) 116 {*movv4hi_store} (expr_list:REG_DEAD (reg:V4HI
> > 105)
> > (nil)))
> >
> > (insn 19 18 20 3 a.c:15 (set (reg:V4HI 106)
> > (mem:V4HI (plus:SI (reg/v/f:SI 100 [ b ])
> > (const_int 8 [0x8])) [2 S8 A64])) 115 {*movv4hi_load}
> > (expr_list:REG_DEAD (reg/v/f:SI 100 [ b ])
> > (nil)))
> >
> > (insn 20 19 58 3 a.c:15 (set (mem:V4HI (plus:SI (reg/v/f:SI 99 [ a ])
> > (const_int 8 [0x8])) [2 S8 A64])
> > (reg:V4HI 106)) 116 {*movv4hi_store} (expr_list:REG_DEAD (reg:V4HI
> > 106)
> > (expr_list:REG_DEAD (reg/v/f:SI 99 [ a ])
> > (nil))))
> >
> > from sched1 - dependecies list:
> > --- Region Dependences --- b 3 bb 0
> > ;; insn code bb dep prio cost reservation
> > ;; ---- ---- -- --- ---- ---- -----------
> > ;; 17 115 3 0 4 1 (2_slots+lsu) : 58 20 18
> > ;; 18 116 3 1 3 1 (2_slots+lsu) : 58 19
> > ;; 19 115 3 1 2 1 (2_slots+lsu) : 58 20
> > ;; 20 116 3 2 1 1 (2_slots+lsu) : 58
> > ;; 58 101 3 4 1 1 (3_slots+pcu) :
> >
> > As you can see, insn 19 is dependant on 18.
> > I think that this should not happen since the arrays has __restrict__.
> > It might have something to do with aliasing.
> >
> > Are you aware of any kind of problems regarding aliasing and vectors?
> > Can you think of anything else that might be wrong in my code that
> > leads gcc to think that there is a dependency between insn 18 and 19?
>
> It completely depends on the GCC version you are using. The
> MEM_EXPRs suggest that it is maybe 4.4 or 4.5 based? Because
> they are not existant. Try recent trunk which should work fine.
>
> Richard.
>
> > Thanks, Roy.
> >
>
I have taken 4.5.0 and I still get the same problem.
Do you have any ideas? Shouldn't the restrict tell the compiler that
there is no dependency between these insns?
Thanks, Roy.
