On Fri, 4 Oct 2019 at 12:18, Richard Biener <rguent...@suse.de> wrote:
>
> On Thu, 3 Oct 2019, Prathamesh Kulkarni wrote:
>
> > On Wed, 2 Oct 2019 at 12:28, Richard Biener <rguent...@suse.de> wrote:
> > >
> > > On Wed, 2 Oct 2019, Prathamesh Kulkarni wrote:
> > >
> > > > On Wed, 2 Oct 2019 at 01:08, Jeff Law <l...@redhat.com> wrote:
> > > > >
> > > > > On 10/1/19 12:40 AM, Richard Biener wrote:
> > > > > > On Mon, 30 Sep 2019, Prathamesh Kulkarni wrote:
> > > > > >
> > > > > >> On Wed, 25 Sep 2019 at 23:44, Richard Biener <rguent...@suse.de>
> > > > > >> wrote:
> > > > > >>>
> > > > > >>> On Wed, 25 Sep 2019, Prathamesh Kulkarni wrote:
> > > > > >>>
> > > > > >>>> On Fri, 20 Sep 2019 at 15:20, Jeff Law <l...@redhat.com> wrote:
> > > > > >>>>>
> > > > > >>>>> On 9/19/19 10:19 AM, Prathamesh Kulkarni wrote:
> > > > > >>>>>> Hi,
> > > > > >>>>>> For PR91532, the dead store is trivially deleted if we place
> > > > > >>>>>> dse pass
> > > > > >>>>>> between ifcvt and vect. Would it be OK to add another instance
> > > > > >>>>>> of dse there ?
> > > > > >>>>>> Or should we add an ad-hoc "basic-block dse" sub-pass to ifcvt
> > > > > >>>>>> that
> > > > > >>>>>> will clean up the dead store ?
> > > > > >>>>> I'd hesitate to add another DSE pass. If there's one nearby
> > > > > >>>>> could we
> > > > > >>>>> move the existing pass?
> > > > > >>>> Well I think the nearest one is just after pass_warn_restrict.
> > > > > >>>> Not
> > > > > >>>> sure if it's a good
> > > > > >>>> idea to move it up from there ?
> > > > > >>>
> > > > > >>> You'll need it inbetween ifcvt and vect so it would be disabled
> > > > > >>> w/o vectorization, so no, that doesn't work.
> > > > > >>>
> > > > > >>> ifcvt already invokes SEME region value-numbering so if we had
> > > > > >>> MESE region DSE it could use that. Not sure if you feel like
> > > > > >>> refactoring DSE to work on regions - it currently uses a DOM
> > > > > >>> walk which isn't suited for that.
> > > > > >>>
> > > > > >>> if-conversion has a little "local" dead predicate compute removal
> > > > > >>> thingy (not that I like that), eventually it can be enhanced to
> > > > > >>> do the DSE you want? Eventually it should be moved after the
> > > > > >>> local
> > > > > >>> CSE invocation though.
> > > > > >> Hi,
> > > > > >> Thanks for the suggestions.
> > > > > >> For now, would it be OK to do "dse" on loop header in
> > > > > >> tree_if_conversion, as in the attached patch ?
> > > > > >> The patch does local dse in a new function ifcvt_local_dse instead
> > > > > >> of
> > > > > >> ifcvt_local_dce, because it needed to be done after RPO VN which
> > > > > >> eliminates:
> > > > > >> Removing dead stmt _ifc__62 = *_55;
> > > > > >> and makes the following store dead:
> > > > > >> *_55 = _ifc__61;
> > > > > >
> > > > > > I suggested trying to move ifcvt_local_dce after RPO VN, you could
> > > > > > try that as independent patch (pre-approved).
> > > > > >
> > > > > > I don't mind the extra walk though.
> > > > > >
> > > > > > What I see as possible issue is that dse_classify_store walks
> > > > > > virtual
> > > > > > uses and I'm not sure if the loop exit is a natural boundary for
> > > > > > such walk (eventually the loop header virtual PHI is reached but
> > > > > > there may also be a loop-closed PHI for the virtual operand,
> > > > > > but not necessarily). So the question is whether to add a
> > > > > > "stop at" argument to dse_classify_store specifying the virtual
> > > > > > use the walk should stop at?
> > > > > I think we want to stop at the block boundary -- aren't the cases we
> > > > > care about here local to a block?
> > > > This version restricts walking in dse_classify_store to basic-block if
> > > > bb_only is true,
> > > > and removes dead stores in ifcvt_local_dce instead of separate walk.
> > > > Does it look OK ?
> > >
> > > As relied to Jeff please make it trivially work for SESE region walks
> > > by specifying the exit virtual operand to stop on.
> > Thanks for the suggestions, does the attached patch look OK ?
> > Um, sorry, I don't really understand why we need to specify virtual
> > phi arg from back edge to stop the walk.
> > Would it achieve the same effect if we pass index of loop->latch to
> > stop the walk ?
>
> Since DSE walks the virtual def->use chain it makes sense to stop
> it at a specific virtual definition. Note
>
> @@ -706,7 +699,9 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
> FOR_EACH_IMM_USE_STMT (use_stmt, ui, defvar)
> {
> /* Limit stmt walking. */
> - if (++cnt > PARAM_VALUE (PARAM_DSE_MAX_ALIAS_QUERIES_PER_STORE))
> + if (++cnt > PARAM_VALUE (PARAM_DSE_MAX_ALIAS_QUERIES_PER_STORE)
> + || (stop_at_vuse
> + && gimple_vuse (use_stmt) == stop_at_vuse))
> {
>
> can be done above this loop:
>
> diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c
> index ba67884a825..bc95c21e52c 100644
> --- a/gcc/tree-ssa-dse.c
> +++ b/gcc/tree-ssa-dse.c
> @@ -701,6 +701,9 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
> }
> else
> defvar = gimple_vdef (temp);
> + /* If we are instructed to stop walking at region boundary, do so.
> */
> + if (defvar == stop_at_vuse)
> + return DSE_STORE_LIVE;
> auto_vec<gimple *, 10> defs;
> gimple *phi_def = NULL;
> FOR_EACH_IMM_USE_STMT (use_stmt, ui, defvar)
>
> The way you find the virtual PHI is also too complicated. I'd do
>
> @@ -2873,7 +2873,7 @@ ifcvt_split_critical_edges (class loop *loop, bool
> aggressive_if_conv)
> loop vectorization. */
>
> static void
> -ifcvt_local_dce (basic_block bb)
> +ifcvt_local_dce (class loop *loop)
> {
> gimple *stmt;
> gimple *stmt1;
> @@ -2890,6 +2890,10 @@ ifcvt_local_dce (basic_block bb)
> replace_uses_by (name_pair->first, name_pair->second);
> redundant_ssa_names.release ();
>
> + /* The loop has a single BB only. */
> + basic_block bb = loop->header;
> + tree latch_vdef = NULL_TREE;
> +
> worklist.create (64);
> /* Consider all phi as live statements. */
> for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
> @@ -2897,6 +2901,8 @@ ifcvt_local_dce (basic_block bb)
> phi = gsi_stmt (gsi);
> gimple_set_plf (phi, GF_PLF_2, true);
> worklist.safe_push (phi);
> + if (virtual_operand_p (gimple_phi_result (phi)))
> + latch_vdef = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
> }
> /* Consider load/store statements, CALL and COND as live. */
> for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
Hi,
Thanks a lot for the suggestions.
Does the attached version look OK ?
Thanks,
Prathamesh
>
>
> > Thanks,
> > Prathamesh
> > >
> > > Richard.
> >
>
> --
> Richard Biener <rguent...@suse.de>
> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
> Germany; GF: Felix Imendörffer; HRB 247165 (AG München)
diff --git a/gcc/tree-if-conv.c b/gcc/tree-if-conv.c
index 822aae5b83f..af49813b0d1 100644
--- a/gcc/tree-if-conv.c
+++ b/gcc/tree-if-conv.c
@@ -120,6 +120,7 @@ along with GCC; see the file COPYING3. If not see
#include "fold-const.h"
#include "tree-ssa-sccvn.h"
#include "tree-cfgcleanup.h"
+#include "tree-ssa-dse.h"
/* Only handle PHIs with no more arguments unless we are asked to by
simd pragma. */
@@ -2873,7 +2874,7 @@ ifcvt_split_critical_edges (class loop *loop, bool aggressive_if_conv)
loop vectorization. */
static void
-ifcvt_local_dce (basic_block bb)
+ifcvt_local_dce (class loop *loop)
{
gimple *stmt;
gimple *stmt1;
@@ -2890,6 +2891,10 @@ ifcvt_local_dce (basic_block bb)
replace_uses_by (name_pair->first, name_pair->second);
redundant_ssa_names.release ();
+ /* The loop has a single BB only. */
+ basic_block bb = loop->header;
+ tree latch_vdef = NULL_TREE;
+
worklist.create (64);
/* Consider all phi as live statements. */
for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
@@ -2897,6 +2902,8 @@ ifcvt_local_dce (basic_block bb)
phi = gsi_stmt (gsi);
gimple_set_plf (phi, GF_PLF_2, true);
worklist.safe_push (phi);
+ if (virtual_operand_p (gimple_phi_result (phi)))
+ latch_vdef = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
}
/* Consider load/store statements, CALL and COND as live. */
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
@@ -2960,6 +2967,19 @@ ifcvt_local_dce (basic_block bb)
while (!gsi_end_p (gsi))
{
stmt = gsi_stmt (gsi);
+ if (gimple_store_p (stmt))
+ {
+ tree lhs = gimple_get_lhs (stmt);
+ ao_ref write;
+ ao_ref_init (&write, lhs);
+
+ if (dse_classify_store (&write, stmt, false, NULL, NULL, latch_vdef)
+ == DSE_STORE_DEAD)
+ delete_dead_or_redundant_assignment (&gsi, "dead");
+ gsi_next (&gsi);
+ continue;
+ }
+
if (gimple_plf (stmt, GF_PLF_2))
{
gsi_next (&gsi);
@@ -3070,7 +3090,7 @@ tree_if_conversion (class loop *loop, vec<gimple *> *preds)
todo |= do_rpo_vn (cfun, loop_preheader_edge (loop), exit_bbs);
/* Delete dead predicate computations. */
- ifcvt_local_dce (loop->header);
+ ifcvt_local_dce (loop);
BITMAP_FREE (exit_bbs);
todo |= TODO_cleanup_cfg;
diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c
index ba67884a825..d8f7089786a 100644
--- a/gcc/tree-ssa-dse.c
+++ b/gcc/tree-ssa-dse.c
@@ -36,6 +36,7 @@ along with GCC; see the file COPYING3. If not see
#include "params.h"
#include "alias.h"
#include "tree-ssa-loop.h"
+#include "tree-ssa-dse.h"
/* This file implements dead store elimination.
@@ -76,21 +77,13 @@ along with GCC; see the file COPYING3. If not see
fact, they are the same transformation applied to different views of
the CFG. */
-static void delete_dead_or_redundant_assignment (gimple_stmt_iterator *, const char *);
+void delete_dead_or_redundant_assignment (gimple_stmt_iterator *, const char *);
static void delete_dead_or_redundant_call (gimple_stmt_iterator *, const char *);
/* Bitmap of blocks that have had EH statements cleaned. We should
remove their dead edges eventually. */
static bitmap need_eh_cleanup;
-/* Return value from dse_classify_store */
-enum dse_store_status
-{
- DSE_STORE_LIVE,
- DSE_STORE_MAYBE_PARTIAL_DEAD,
- DSE_STORE_DEAD
-};
-
/* STMT is a statement that may write into memory. Analyze it and
initialize WRITE to describe how STMT affects memory.
@@ -662,10 +655,10 @@ dse_optimize_redundant_stores (gimple *stmt)
if only clobber statements influenced the classification result.
Returns the classification. */
-static dse_store_status
+dse_store_status
dse_classify_store (ao_ref *ref, gimple *stmt,
bool byte_tracking_enabled, sbitmap live_bytes,
- bool *by_clobber_p = NULL)
+ bool *by_clobber_p, tree stop_at_vuse)
{
gimple *temp;
int cnt = 0;
@@ -701,6 +694,11 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
}
else
defvar = gimple_vdef (temp);
+
+ /* If we're instructed to stop walking at region boundary, do so. */
+ if (defvar == stop_at_vuse)
+ return DSE_STORE_LIVE;
+
auto_vec<gimple *, 10> defs;
gimple *phi_def = NULL;
FOR_EACH_IMM_USE_STMT (use_stmt, ui, defvar)
@@ -901,7 +899,7 @@ delete_dead_or_redundant_call (gimple_stmt_iterator *gsi, const char *type)
/* Delete a dead store at GSI, which is a gimple assignment. */
-static void
+void
delete_dead_or_redundant_assignment (gimple_stmt_iterator *gsi, const char *type)
{
gimple *stmt = gsi_stmt (*gsi);
diff --git a/gcc/tree-ssa-dse.h b/gcc/tree-ssa-dse.h
new file mode 100644
index 00000000000..65be5667cd5
--- /dev/null
+++ b/gcc/tree-ssa-dse.h
@@ -0,0 +1,17 @@
+#ifndef TREE_SSA_DSE_H
+#define TREE_SSA_DSE_H
+
+/* Return value from dse_classify_store */
+enum dse_store_status
+{
+ DSE_STORE_LIVE,
+ DSE_STORE_MAYBE_PARTIAL_DEAD,
+ DSE_STORE_DEAD
+};
+
+dse_store_status dse_classify_store (ao_ref *, gimple *, bool, sbitmap,
+ bool * = NULL, tree = NULL);
+
+void delete_dead_or_redundant_assignment (gimple_stmt_iterator *, const char *);
+
+#endif
