[LLVMdev] MemoryDependenceAnalysis

[Chris Lattner]

On Apr 13, 2009, at 9:06 AM, Anthony Danalis wrote:
> Hello,
>
> I have a code similar to the following:

Hi Anthony,

Can you please attach the .bc file for this?

-Chris

>
>
>         program test
>             integer i, j, N
>             real B(10)
>
>             call bar(N, 8)
>             N = N+1
>             do i = 1, N
>                 B(i) = (i+5)/(i+3)
>             enddo
>
>             j = N/2
>             N = N+7
>
>             call IMPORTANT_F(B, N, i, j)
>
>         end program
>
> and I am trying to use dependence analysis on the second and fourth
> actual parameters of IMPORTANT_F().  Since it's Fortran, they are
> really pointers, and the IR of the last block looks like this:
>
>         %11 = sdiv i32 %1, 2            ; <i32> [#uses=1]
>         store i32 %11, i32* %j, align 4
>         %12 = add i32 %0, 8             ; <i32> [#uses=1]
>         store i32 %12, i32* %n, align 4
>         call void (...)* @IMPORTANT_F_([10 x float]* %b, i32* %n,
> i32* %i, i32* %j) nounwind
>         ret void
>
> My problem is that if I use getNonLocalPointerDependency() I get the
> instruction "N=N+1" as a Def for the second parameter, "N",  and no
> Def for the fourth, "j", (only the call to "bar()" as clobber).
> If I use getDependency() on the call, I get the instruction "N=N+7" as
> a clobber.
>
> How can I use MemoryDependenceAnalysis (or any other analysis for that
> matter) to gather that the instructions
> j = N/2  (store i32 %11, i32* %j, align 4)
> and
> N = N+7  (store i32 %12, i32* %n, align 4)
> are the ones that define the parameters "j" and "N" respectively?
>
> thanks,
> Anthony
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