Re: Value Range Propagation Patch (Version 3)

[Toon Moene <toon at moene dot indiv dot nluug dot nl>]

John Wehle wrote:

> I wrote:

> > Or is the VRP code unable to determine the range of the biv I ?
> 
> Yes.  There are two reasons for this.
> 
>   1) I didn't implement the code to compute the min and max for loop
>      counters until after I posted version 3.  Attached is the current
>      (rather untested) version of vrp.c which when given:

[ ... example elided - the code bootstrapped correctly, btw, on
      alphaev6-unknown-linux-gnu ... ]

>      is able to remove the call to abort.  And given your example code it
>      does determines that the loop counter ranges from 0 to 9.

Yep, unfortunately, in Fortran as implemented in the current frontend, I
isn't the loop counter.  The loop counter is an abstract thingy that for
a loop:

      DO I = N1, N2, N3   ! Loop from N1 to N2 with step N3
         ....
      ENDDO

runs from MAX(N2 - N1 + N3) / N3, 0) to zero, while I runs from N1 to N1
+ (MAX(N2 - N1 + N3) / N3, 0) - 1) * N3.  Perhaps that's just too much
to ask from VRP.

Thanks for the explanation.

-- 
Toon Moene - mailto:toon@moene.indiv.nluug.nl - phoneto: +31 346 214290
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