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Re: -fprefetch-loop-arrays on PowerPC


> Hello,
> 
> thanks for the great new GCC 3.1.
> 
> I have tried the new -fprefetch-loop-arrays optimizer option.
> It is very nice to have it. I know this is a young feature perhaps this
> helps improving it.
> 
> The generated assembler code contains the following, in my oppinion
> suboptimal, instruction sequences:
> 
> L..19202:
>         addic. 5,5,-1
>         lwz 3,0(6)
>         addi 12,12,16
>         lwz 9,4(6)
>         lwz 11,8(6)
>         lwz 30,12(6)
>         addi 6,6,16
>         stw 3,0(8)
>         stw 9,4(8)
>         stw 11,8(8)
>         stw 30,12(8)
>         addi 8,8,16
>         dcbt 0,20        < is the impact of this instruction a subset of
>                          < the next instruction?
>         dcbtst 0,20      <
>         ble- 0,L..19176

Sometimes gcc suceeds to confuse itself to believe that accesses to same
array are disjunct.  WOuld be possible to see the source?

Honza


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