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?
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,
