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Re: [PATCH] tree level if-conversion for vectorizer



On Sep 1, 2004, at 1:04 AM, Ayal Zaks wrote:



Richard Henderson <rth@redhat.com> wrote on 31/08/2004 09:36:08:


On Mon, Aug 30, 2004 at 10:40:16PM -0700, Devang Patel wrote:
OK. But as you say, how to handle PARM_DECL ?

T3 = P ? T2 : T1.


In the case of PARM_DECL, T1 as the default definition *does* have
a defined meaning -- the value of the parameter as given by the caller.


   if (COND)
      A[i] = x;

do you think, we should introduce temp. here, like

   t = A[i];
   if (COND)
      t = x;
   A[i] = t;

For a conditional store, you must either do this or fail the transform.
There are no other alternatives.

There may be another alternative for conditional stores. If the compiler
has some scratch-pad address, into which it can always store without
causing any trouble, we could do


      t = (COND ? &A[i] : scratch-pad-address)
      *t = x

which also applies to conditional loads.

One intermediate step is to check for symmetric loads and stores.


-
Devang


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