[PATCH] alignment and loop peeling (vectorization)

[Devang Patel <dpatel at apple dot com>]

:ADDPATCH SSA (vectorizer):

Hi All,

This has been discussed in few threads ...

  http://gcc.gnu.org/ml/gcc-patches/2006-01/msg02246.html
  http://gcc.gnu.org/ml/gcc-patches/2006-02/msg01715.html

Vectorizer uses loop peeling technique to peel N loop iterations to  
reach vector alignment. At the moment, it assumes that vector  
alignment will be reached after N iterations. And when it does not,  
program usually crashes at runtime.

However, when initial data reference misalignment is known it is  
possible to decide, at compile time, whether vector alignment is  
reachable using N number of iterations or not. If it is not possible  
then loop peeling transformation is not applied. (Earlier I prepared  
small patch for this case - msg02246.html. It is not yet OKed for  
mainline, so I am including it in this patch also).

New target hook is added when initial data ref  alignment is unknown  
at compile time. This target hook determines whether vector alignment  
is reachable at runtime or not based on current alignment mode and  
scalar base type info. RS6000/darwin specific target hooks is  
provided with this patch. Default target hook is provided for targets  
that does not have specialized hooks.

Bootstrapped and tested on powerpc-darwin.

OK for mainline ?
Thanks,
-
Devang

2006-03-02  Devang Patel  <dpatel@apple.com>
            Dorit Nuzman  <dorit@il.ibm.com>

        * targethooks.c (default_vector_alignment_reachable): New.
        * targethooks.h (default_vector_alignment_reachable,
        vector_alignment_reachable): Declare.
        * target.h (vector_alignment_reachable): New member for  
targetm.vectorize.
        * tree-vect-analyze.c (vect_enhance_data_refs_alignment):  
Avoid peeling
        when vector alignment is not reachable.
        (target.h): Include.
        * target-def.h (TARGET_VECTOR_ALIGNMENT_REACHABLE): New.
        * Makefile.in (tree-vect-analyze.c): Depend on target.h
        * config/rs6000/rs6000.c  
(rs6000_vector_alignment_reachable): New.
        (TARGET_VECTOR_ALIGNMENT_REACHABLE): Define.

        * gcc.dg/vect/vect-align-1.c: New.
        * gcc.dg/vect/vect-align-2.c: New.

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