Re: question about __builtin_prefetch for gcc 3.1

[Ravikiran G Thirumalai <kiran at in dot ibm dot com>]

Ooops ...... I should've used -mcpu=pentium3.  
I should've read the gcc archives before posting.  Sorry folks.

-Kiran

On Tue, Jul 23, 2002 at 02:25:54PM +0530, Ravikiran G Thirumalai wrote:
> Tried the foll query at gcc-help with no avail :(.
> Hope somebody here can throw some light on this.
> 
> TIA
> Kiran
> 
> ----- Forwarded message from Ravikiran G Thirumalai <kiran@in.ibm.com> -----
> 
> > Date: Wed, 17 Jul 2002 15:55:09 +0530
> > From: Ravikiran G Thirumalai <kiran@in.ibm.com>
> > To: gcc-help@gcc.gnu.org
> > Subject: question about __builtin_prefetch for gcc 3.1,
> > User-Agent: Mutt/1.2.5i
> > 
> > Hi,
> > I was trying out the "__builtin_prefetch" feature in gcc3.1 (gcc-3.1-7.i386.rpm
> >  - Rawhide) i just installed. 
> > 
> > I used the foll code snippet to see if "prefetch" insn was being generated --
> > <snippet>
> > 
> >  
> > #define prefetchw(x) __builtin_prefetch(x, 1, 0)
> >  
> > int main()
> > {
> >         element_t *temp;
> >         create_list(LIST_NOS);
> >  
> >         temp = head;
> >         while( temp != NULL) {
> >                 int burn;
> >                 prefetchw(temp->next);
> >                 burn = test_rand()* test_rand();
> >                 temp->member_int *= burn;
> >                 temp = temp->next;
> >         }
> >  
> >         destroy_list();
> >         return 0;
> > }
> > 
> > </snippet>
> > 
> > Surprisingly, the objdump disassembly does not show "prefetch" insn at all.
> > Am I doing something stupid here??? or is the builtin broken??
> > 
> > Here is some more arch info:
> > 
> > Procesor:
> > ---------
> > processor       : 0
> > vendor_id       : GenuineIntel
> > cpu family      : 6
> > model           : 8
> > model name      : Pentium III (Coppermine)
> > stepping        : 10
> > cpu MHz         : 996.797
> > cache size      : 256 KB
> > fdiv_bug        : no
> > hlt_bug         : no
> > f00f_bug        : no
> > coma_bug        : no
> > fpu             : yes
> > fpu_exception   : yes
> > cpuid level     : 2
> > wp              : yes
> > flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse
> > bogomips        : 1985.74
> > 
> > Command used for compilaion:
> > ----------------------------
> > gcc -O2 prefetch.c -o prefetch -Wall -march=i686     
> > 
> > objdump output:
> > ---------------
> > 08048410 <main>:
> >  8048410:       55                      push   %ebp
> >  8048411:       89 e5                   mov    %esp,%ebp
> >  8048413:       83 ec 08                sub    $0x8,%esp
> >  8048416:       83 e4 f0                and    $0xfffffff0,%esp
> >  8048419:       c7 04 24 64 00 00 00    movl   $0x64,(%esp,1)
> >  8048420:       e8 6b ff ff ff          call   8048390 <create_list>
> >  8048425:       8b 0d d8 94 04 08       mov    0x80494d8,%ecx
> >  804842b:       85 c9                   test   %ecx,%ecx
> >  804842d:       74 47                   je     8048476 <main+0x66>
> >  804842f:       90                      nop
> >  8048430:       a1 dc 94 04 08          mov    0x80494dc,%eax
> >  8048435:       69 c0 6d 4e c6 41       imul   $0x41c64e6d,%eax,%eax
> >  804843b:       05 39 30 00 00          add    $0x3039,%eax
> >  8048440:       89 c2                   mov    %eax,%edx
> >  8048442:       69 c0 6d 4e c6 41       imul   $0x41c64e6d,%eax,%eax
> >  8048448:       c1 fa 10                sar    $0x10,%edx
> >  804844b:       81 e2 ff 7f 00 00       and    $0x7fff,%edx
> >  8048451:       05 39 30 00 00          add    $0x3039,%eax
> >  8048456:       a3 dc 94 04 08          mov    %eax,0x80494dc
> >  804845b:       c1 f8 10                sar    $0x10,%eax
> >  804845e:       25 ff 7f 00 00          and    $0x7fff,%eax
> >  8048463:       0f af d0                imul   %eax,%edx
> >  8048466:       8b 41 14                mov    0x14(%ecx),%eax
> >  8048469:       0f af d0                imul   %eax,%edx
> >  804846c:       89 51 14                mov    %edx,0x14(%ecx)
> >  804846f:       8b 49 18                mov    0x18(%ecx),%ecx
> >  8048472:       85 c9                   test   %ecx,%ecx
> >  8048474:       75 ba                   jne    8048430 <main+0x20>
> >  8048476:       e8 65 ff ff ff          call   80483e0 <destroy_list>
> >  804847b:       c9                      leave
> >  804847c:       31 c0                   xor    %eax,%eax
> >  804847e:       c3                      ret
> >  804847f:       90                      nop
> > 
> > 
> > TIA
> > -Kiran
> 
> ----- End forwarded message -----
> 

-- 
Ravikiran G Thirumalai <kiran@in.ibm.com>
Linux Technology Center, IBM Software Labs,
Bangalore.