On Thu, Sep 15, 2016 at 12:07 PM, Bin Cheng <bin.ch...@arm.com> wrote:
> Hi,
> This patch fixes PR77503.  Root cause is loop peeling changes the initial 
> value for reduction PHI node, resulting in different statement for 
> vect_transform_stmt to vect_analyze_stmt.  Similar issue stands for loop 
> control IV, we record the original information in 
> LOOP_PHI_EVOLUTION_BASE_UNCHANGED for that.  This patch follows the same 
> method by recording reduction code for CONST_COND_REDUCTION at analysis stage 
> and use the information at transform stage.  The only difference is we need 
> record it in stmt_vec_info because there might be multiple reductions.  
> Unfortunately this requires additional memory for each statement, I didn't 
> see easy way out.  Maybe it's possible to improve vectorizer so it 
> caches/reuses information from analysis stage to transform stage?
> Bootstrap and test on x86_64 and AArch64 ongoing.  Is it OK if no regression?


As for improving stmt_info size and caching info from analysis phase
-- yes, ideally stmt_info would have
most of its contents discriminated on STMT_VINFO_TYPE using a union of
type specific fields.  Note that
this kind of refactoring would be way easier than trying to make it a
class using inheritance (you'd need to
defer vinfo creation until analysis figured out the info or add an
indirection to type specific data).

stmt_info isn't very well packed either so the general answer for now
is -- we don't care about its size.

As for re-using data from analysis phase -- yes!  That we share the
"head" of all vectorizable_* routines
for both analysis and transform phase was a bad design decision --
ideally we'd have vectorizable_*
routines w/o transform and then vectorize_* routines which only do the
transform based on data recorded
during analysis phase.

Both refactorings are very welcome (esp. the latter which eventually
means adding many more fields to


> Thanks,
> bin
> 2016-09-07  Bin Cheng  <bin.ch...@arm.com>
>         PR tree-optimization/77503
>         * tree-vect-loop.c (vectorizable_reduction): Record reduction
>         code for CONST_COND_REDUCTION at analysis stage and use it at
>         transform stage.
>         * tree-vectorizer.h (struct _stmt_vec_info): New field.
>         * tree-vect-stmts.c (new_stmt_vec_info): Initialize above new
>         field.
> gcc/testsuite/ChangeLog
> 2016-09-07  Bin Cheng  <bin.ch...@arm.com>
>         PR tree-optimization/77503
>         * gcc.dg/vect/pr77503.c: New test.

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