Re: [PATCH] Try fix PR90911

[Richard Biener <rguenther at suse dot de>]

On Tue, 25 Jun 2019, Richard Biener wrote:

> 
> PR90911 reports a slowdown of 456.hmmer with the recent introduction
> of vectorizer versioning of outer loops, more specifically the case
> of re-using if-conversion created versions.
> 
> The patch below fixes things up to adjust the edge probability
> and scale the loop bodies in two steps, delaying scalar_loop
> scaling until all peeling is done.  This restores profile-mismatches
> to the same state as it was on the GCC 9 branch and seems to
> fix the observed slowdown of 456.hmmer.
> 
> Boostrap & regtest running on x86_64-unknown-linux-gnu.
> 
> Honza, does this look OK?

Ping.

> Thanks,
> Richard.
> 
> 2019-06-25  Richard Biener  <rguenther@suse.de>
> 
> 	* tree-vectorizer.h (_loop_vec_info::scalar_loop_scaling): New field.
> 	(LOOP_VINFO_SCALAR_LOOP_SCALING): new.
> 	* tree-vect-loop.c (_loop_vec_info::_loop_vec_info): Initialize
> 	scalar_loop_scaling.
> 	(vect_transform_loop): Scale scalar loop profile if needed.
> 	* tree-vect-loop-manip.c (vect_loop_versioning): When re-using
> 	the loop copy from if-conversion adjust edge probabilities
> 	and scale the vectorized loop body profile, queue the scalar
> 	profile for updating after peeling.
> 
> Index: gcc/tree-vectorizer.h
> ===================================================================
> --- gcc/tree-vectorizer.h	(revision 272636)
> +++ gcc/tree-vectorizer.h	(working copy)
> @@ -548,6 +548,9 @@ typedef struct _loop_vec_info : public v
>    /* Mark loops having masked stores.  */
>    bool has_mask_store;
>  
> +  /* Queued scaling factor for the scalar loop.  */
> +  profile_probability scalar_loop_scaling;
> +
>    /* If if-conversion versioned this loop before conversion, this is the
>       loop version without if-conversion.  */
>    struct loop *scalar_loop;
> @@ -603,6 +606,7 @@ typedef struct _loop_vec_info : public v
>  #define LOOP_VINFO_PEELING_FOR_NITER(L)    (L)->peeling_for_niter
>  #define LOOP_VINFO_NO_DATA_DEPENDENCIES(L) (L)->no_data_dependencies
>  #define LOOP_VINFO_SCALAR_LOOP(L)	   (L)->scalar_loop
> +#define LOOP_VINFO_SCALAR_LOOP_SCALING(L)  (L)->scalar_loop_scaling
>  #define LOOP_VINFO_HAS_MASK_STORE(L)       (L)->has_mask_store
>  #define LOOP_VINFO_SCALAR_ITERATION_COST(L) (L)->scalar_cost_vec
>  #define LOOP_VINFO_SINGLE_SCALAR_ITERATION_COST(L) (L)->single_scalar_iteration_cost
> Index: gcc/tree-vect-loop.c
> ===================================================================
> --- gcc/tree-vect-loop.c	(revision 272636)
> +++ gcc/tree-vect-loop.c	(working copy)
> @@ -835,6 +835,7 @@ _loop_vec_info::_loop_vec_info (struct l
>      operands_swapped (false),
>      no_data_dependencies (false),
>      has_mask_store (false),
> +    scalar_loop_scaling (profile_probability::uninitialized ()),
>      scalar_loop (NULL),
>      orig_loop_info (NULL)
>  {
> @@ -8562,6 +8563,10 @@ vect_transform_loop (loop_vec_info loop_
>    epilogue = vect_do_peeling (loop_vinfo, niters, nitersm1, &niters_vector,
>  			      &step_vector, &niters_vector_mult_vf, th,
>  			      check_profitability, niters_no_overflow);
> +  if (LOOP_VINFO_SCALAR_LOOP (loop_vinfo)
> +      && LOOP_VINFO_SCALAR_LOOP_SCALING (loop_vinfo).initialized_p ())
> +    scale_loop_frequencies (LOOP_VINFO_SCALAR_LOOP (loop_vinfo),
> +			    LOOP_VINFO_SCALAR_LOOP_SCALING (loop_vinfo));
>  
>    if (niters_vector == NULL_TREE)
>      {
> Index: gcc/tree-vect-loop-manip.c
> ===================================================================
> --- gcc/tree-vect-loop-manip.c	(revision 272636)
> +++ gcc/tree-vect-loop-manip.c	(working copy)
> @@ -3114,8 +3114,17 @@ vect_loop_versioning (loop_vec_info loop
>  				 GSI_SAME_STMT);
>  	}
>  
> -      /* ???  if-conversion uses profile_probability::always () but
> -         prob below is profile_probability::likely ().  */
> +      /* if-conversion uses profile_probability::always () for both paths,
> +	 reset the paths probabilities appropriately.  */
> +      edge te, fe;
> +      extract_true_false_edges_from_block (condition_bb, &te, &fe);
> +      te->probability = prob;
> +      fe->probability = prob.invert ();
> +      /* We can scale loops counts immediately but have to postpone
> +         scaling the scalar loop because we re-use it during peeling.  */
> +      scale_loop_frequencies (loop_to_version, prob);
> +      LOOP_VINFO_SCALAR_LOOP_SCALING (loop_vinfo) = prob.invert ();
> +
>        nloop = scalar_loop;
>        if (dump_enabled_p ())
>  	dump_printf_loc (MSG_NOTE, vect_location,
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)