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