re PR tree-optimization/91532 ([SVE] Redundant predicated store in gcc.target/aarch64/fmla_2.c)

2019-10-07  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
	    Richard Biener  <rguenther@suse.de>

	PR tree-optimization/91532
	* tree-if-conv.c: Include tree-ssa-dse.h.
	(ifcvt_local_dce): Change param from bb to loop,
	and call dse_classify_store.
	(tree_if_conversion): Pass loop instead of loop->header as arg
	to ifcvt_local_dce.
	* tree-ssa-dse.c: Include tree-ssa-dse.h.
	(delete_dead_or_redundant_assignment): Remove static qualifier from
	declaration, and add prototype in tree-ssa-dse.h.
	(dse_store_status): Move to tree-ssa-dse.h.
	(dse_classify_store): Remove static qualifier and add new tree param
	stop_at_vuse, and add prototype in tree-ssa-dse.h.
	* tree-ssa-dse.h: New header.

Co-Authored-By: Richard Biener <rguenther@suse.de>

From-SVN: r276681

gcc/ChangeLog

+2019-10-07  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
+	    Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/91532
+	* tree-if-conv.c: Include tree-ssa-dse.h.
+	(ifcvt_local_dce): Change param from bb to loop,
+	and call dse_classify_store.
+	(tree_if_conversion): Pass loop instead of loop->header as arg
+	to ifcvt_local_dce.
+	* tree-ssa-dse.c: Include tree-ssa-dse.h.
+	(delete_dead_or_redundant_assignment): Remove static qualifier from
+	declaration, and add prototype in tree-ssa-dse.h.
+	(dse_store_status): Move to tree-ssa-dse.h.
+	(dse_classify_store): Remove static qualifier and add new tree param
+	stop_at_vuse, and add prototype in tree-ssa-dse.h.
+	* tree-ssa-dse.h: New header.
+
 2019-10-07  Iain Sandoe  <iain@sandoe.co.uk>
 
 	* config/darwin.c (machopic_output_indirection): Don't put

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;

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);

gcc/tree-ssa-dse.h

+/* Support routines for dead store elimination. 
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_TREE_SSA_DSE_H
+#define GCC_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   /* GCC_TREE_SSA_DSE_H  */