re PR debug/54971 (SRA pessimizes debug info by not creating debug stmts for fields without replacements)

2012-10-26  Martin Jambor  <mjambor@suse.cz>

	PR debug/54971
	* tree-sra.c (struct access): New flag grp_to_be_debug_replaced.
	(dump_access): Dump the new flag.
	(analyze_access_subtree): Set the new flag when appropriate.
	(create_access_replacement): Handle debug replacements differently.
	(generate_subtree_copies): Handle the grp_to_be_debug_replaced flag.
	(init_subtree_with_zero): Likewise.
	(sra_modify_expr): Likewise.
	(load_assign_lhs_subreplacements): Likewise.
	(sra_modify_assign): Likewise.

From-SVN: r192848

gcc/ChangeLog

@@ -1,3 +1,16 @@
+2012-10-26  Martin Jambor  <mjambor@suse.cz>
+
+	PR debug/54971
+	* tree-sra.c (struct access): New flag grp_to_be_debug_replaced.
+	(dump_access): Dump the new flag.
+	(analyze_access_subtree): Set the new flag when appropriate.
+	(create_access_replacement): Handle debug replacements differently.
+	(generate_subtree_copies): Handle the grp_to_be_debug_replaced flag.
+	(init_subtree_with_zero): Likewise.
+	(sra_modify_expr): Likewise.
+	(load_assign_lhs_subreplacements): Likewise.
+	(sra_modify_assign): Likewise.
+
 2012-10-23  Yuri Rumyantsev  <ysrumyan@gmail.com>
 
 	* config/i386/i386.c (insn_is_function_arg) : Add check on CALL

gcc/tree-sra.c

@@ -227,6 +227,10 @@ struct access
   /* Set when a scalar replacement should be created for this variable.  */
   unsigned grp_to_be_replaced : 1;
 
+  /* Set when we want a replacement for the sole purpose of having it in
+     generated debug statements.  */
+  unsigned grp_to_be_debug_replaced : 1;
+
   /* Should TREE_NO_WARNING of a replacement be set?  */
   unsigned grp_no_warning : 1;
 
@@ -390,7 +394,7 @@ dump_access (FILE *f, struct access *access, bool grp)
 	     "grp_hint = %d, grp_covered = %d, "
 	     "grp_unscalarizable_region = %d, grp_unscalarized_data = %d, "
 	     "grp_partial_lhs = %d, grp_to_be_replaced = %d, "
-	     "grp_maybe_modified = %d, "
+	     "grp_to_be_debug_replaced = %d, grp_maybe_modified = %d, "
 	     "grp_not_necessarilly_dereferenced = %d\n",
 	     access->grp_read, access->grp_write, access->grp_assignment_read,
 	     access->grp_assignment_write, access->grp_scalar_read,
@@ -398,7 +402,7 @@ dump_access (FILE *f, struct access *access, bool grp)
 	     access->grp_hint, access->grp_covered,
 	     access->grp_unscalarizable_region, access->grp_unscalarized_data,
 	     access->grp_partial_lhs, access->grp_to_be_replaced,
-	     access->grp_maybe_modified,
+	     access->grp_to_be_debug_replaced, access->grp_maybe_modified,
 	     access->grp_not_necessarilly_dereferenced);
   else
     fprintf (f, ", write = %d, grp_total_scalarization = %d, "
@@ -1528,6 +1532,43 @@ build_ref_for_model (location_t loc, tree base, HOST_WIDE_INT offset,
 				 gsi, insert_after);
 }
 
+/* Attempt to build a memory reference that we could but into a gimple
+   debug_bind statement.  Similar to build_ref_for_model but punts if it has to
+   create statements and return s NULL instead.  This function also ignores
+   alignment issues and so its results should never end up in non-debug
+   statements.  */
+
+static tree
+build_debug_ref_for_model (location_t loc, tree base, HOST_WIDE_INT offset,
+			   struct access *model)
+{
+  HOST_WIDE_INT base_offset;
+  tree off;
+
+  if (TREE_CODE (model->expr) == COMPONENT_REF
+      && DECL_BIT_FIELD (TREE_OPERAND (model->expr, 1)))
+    return NULL_TREE;
+
+  base = get_addr_base_and_unit_offset (base, &base_offset);
+  if (!base)
+    return NULL_TREE;
+  if (TREE_CODE (base) == MEM_REF)
+    {
+      off = build_int_cst (TREE_TYPE (TREE_OPERAND (base, 1)),
+			   base_offset + offset / BITS_PER_UNIT);
+      off = int_const_binop (PLUS_EXPR, TREE_OPERAND (base, 1), off);
+      base = unshare_expr (TREE_OPERAND (base, 0));
+    }
+  else
+    {
+      off = build_int_cst (reference_alias_ptr_type (base),
+			   base_offset + offset / BITS_PER_UNIT);
+      base = build_fold_addr_expr (unshare_expr (base));
+    }
+
+  return fold_build2_loc (loc, MEM_REF, model->type, base, off);
+}
+
 /* Construct a memory reference consisting of component_refs and array_refs to
    a part of an aggregate *RES (which is of type TYPE).  The requested part
    should have type EXP_TYPE at be the given OFFSET.  This function might not
@@ -1861,7 +1902,13 @@ create_access_replacement (struct access *access)
 {
   tree repl;
 
-  repl = create_tmp_var (access->type, "SR");
+  if (access->grp_to_be_debug_replaced)
+    {
+      repl = create_tmp_var_raw (access->type, NULL);
+      DECL_CONTEXT (repl) = current_function_decl;
+    }
+  else
+    repl = create_tmp_var (access->type, "SR");
   if (TREE_CODE (access->type) == COMPLEX_TYPE
       || TREE_CODE (access->type) == VECTOR_TYPE)
     {
@@ -1930,12 +1977,22 @@ create_access_replacement (struct access *access)
 
   if (dump_file)
     {
-      fprintf (dump_file, "Created a replacement for ");
+      if (access->grp_to_be_debug_replaced)
-      print_generic_expr (dump_file, access->base, 0);
+	{
-      fprintf (dump_file, " offset: %u, size: %u: ",
+	  fprintf (dump_file, "Created a debug-only replacement for ");
-	       (unsigned) access->offset, (unsigned) access->size);
+	  print_generic_expr (dump_file, access->base, 0);
-      print_generic_expr (dump_file, repl, 0);
+	  fprintf (dump_file, " offset: %u, size: %u\n",
-      fprintf (dump_file, "\n");
+		   (unsigned) access->offset, (unsigned) access->size);
+	}
+      else
+	{
+	  fprintf (dump_file, "Created a replacement for ");
+	  print_generic_expr (dump_file, access->base, 0);
+	  fprintf (dump_file, " offset: %u, size: %u: ",
+		   (unsigned) access->offset, (unsigned) access->size);
+	  print_generic_expr (dump_file, repl, 0);
+	  fprintf (dump_file, "\n");
+	}
     }
   sra_stats.replacements++;
 
@@ -2144,6 +2201,23 @@ analyze_access_subtree (struct access *root, struct access *parent,
     }
   else
     {
+      if (MAY_HAVE_DEBUG_STMTS && allow_replacements
+	  && scalar && !root->first_child
+	  && (root->grp_scalar_write || root->grp_assignment_write))
+	{
+	  gcc_checking_assert (!root->grp_scalar_read
+			       && !root->grp_assignment_read);
+	  root->grp_to_be_debug_replaced = 1;
+	  if (dump_file && (dump_flags & TDF_DETAILS))
+	    {
+	      fprintf (dump_file, "Marking ");
+	      print_generic_expr (dump_file, root->base, 0);
+	      fprintf (dump_file, " offset: %u, size: %u ",
+		       (unsigned) root->offset, (unsigned) root->size);
+	      fprintf (dump_file, " to be replaced with debug statements.\n");
+	    }
+	}
+
       if (covered_to < limit)
 	hole = true;
       if (scalar)
@@ -2504,6 +2578,22 @@ generate_subtree_copies (struct access *access, tree agg,
 	  update_stmt (stmt);
 	  sra_stats.subtree_copies++;
 	}
+      else if (write
+	       && access->grp_to_be_debug_replaced
+	       && (chunk_size == 0
+		   || access->offset + access->size > start_offset))
+	{
+	  gimple ds;
+	  tree drhs = build_debug_ref_for_model (loc, agg,
+						 access->offset - top_offset,
+						 access);
+	  ds = gimple_build_debug_bind (get_access_replacement (access),
+					drhs, gsi_stmt (*gsi));
+	  if (insert_after)
+	    gsi_insert_after (gsi, ds, GSI_NEW_STMT);
+	  else
+	    gsi_insert_before (gsi, ds, GSI_SAME_STMT);
+	}
 
       if (access->first_child)
 	generate_subtree_copies (access->first_child, agg, top_offset,
@@ -2540,6 +2630,16 @@ init_subtree_with_zero (struct access *access, gimple_stmt_iterator *gsi,
       update_stmt (stmt);
       gimple_set_location (stmt, loc);
     }
+  else if (access->grp_to_be_debug_replaced)
+    {
+      gimple ds = gimple_build_debug_bind (get_access_replacement (access),
+					   build_zero_cst (access->type),
+					   gsi_stmt (*gsi));
+      if (insert_after)
+	gsi_insert_after (gsi, ds, GSI_NEW_STMT);
+      else
+	gsi_insert_before (gsi, ds, GSI_SAME_STMT);
+    }
 
   for (child = access->first_child; child; child = child->next_sibling)
     init_subtree_with_zero (child, gsi, insert_after, loc);
@@ -2646,6 +2746,13 @@ sra_modify_expr (tree *expr, gimple_stmt_iterator *gsi, bool write)
 	*expr = repl;
       sra_stats.exprs++;
     }
+  else if (write && access->grp_to_be_debug_replaced)
+    {
+      gimple ds = gimple_build_debug_bind (get_access_replacement (access),
+					   NULL_TREE,
+					   gsi_stmt (*gsi));
+      gsi_insert_after (gsi, ds, GSI_NEW_STMT);
+    }
 
   if (access->first_child)
     {
@@ -2721,10 +2828,11 @@ load_assign_lhs_subreplacements (struct access *lacc, struct access *top_racc,
   location_t loc = gimple_location (gsi_stmt (*old_gsi));
   for (lacc = lacc->first_child; lacc; lacc = lacc->next_sibling)
     {
+      HOST_WIDE_INT offset = lacc->offset - left_offset + top_racc->offset;
+
       if (lacc->grp_to_be_replaced)
 	{
 	  struct access *racc;
-	  HOST_WIDE_INT offset = lacc->offset - left_offset + top_racc->offset;
 	  gimple stmt;
 	  tree rhs;
 
@@ -2764,10 +2872,34 @@ load_assign_lhs_subreplacements (struct access *lacc, struct access *top_racc,
 	  update_stmt (stmt);
 	  sra_stats.subreplacements++;
 	}
-      else if (*refreshed == SRA_UDH_NONE
+      else
-	       && lacc->grp_read && !lacc->grp_covered)
+	{
-	*refreshed = handle_unscalarized_data_in_subtree (top_racc,
+	  if (*refreshed == SRA_UDH_NONE
-							  old_gsi);
+	      && lacc->grp_read && !lacc->grp_covered)
+	    *refreshed = handle_unscalarized_data_in_subtree (top_racc,
+							      old_gsi);
+	  if (lacc && lacc->grp_to_be_debug_replaced)
+	    {
+	      gimple ds;
+	      tree drhs;
+	      struct access *racc = find_access_in_subtree (top_racc, offset,
+							    lacc->size);
+
+	      if (racc && racc->grp_to_be_replaced)
+		drhs = get_access_replacement (racc);
+	      else if (*refreshed == SRA_UDH_LEFT)
+		drhs = build_debug_ref_for_model (loc, lacc->base, lacc->offset,
+						  lacc);
+	      else if (*refreshed == SRA_UDH_RIGHT)
+		drhs = build_debug_ref_for_model (loc, top_racc->base, offset,
+						  lacc);
+	      else
+		drhs = NULL_TREE;
+	      ds = gimple_build_debug_bind (get_access_replacement (lacc),
+					    drhs, gsi_stmt (*old_gsi));
+	      gsi_insert_after (new_gsi, ds, GSI_NEW_STMT);
+	    }
+	}
 
       if (lacc->first_child)
 	load_assign_lhs_subreplacements (lacc, top_racc, left_offset,
@@ -2982,6 +3114,13 @@ sra_modify_assign (gimple *stmt, gimple_stmt_iterator *gsi)
 	}
     }
 
+  if (lacc && lacc->grp_to_be_debug_replaced)
+    {
+      gimple ds = gimple_build_debug_bind (get_access_replacement (lacc),
+					   unshare_expr (rhs), *stmt);
+      gsi_insert_before (gsi, ds, GSI_SAME_STMT);
+    }
+
   /* From this point on, the function deals with assignments in between
      aggregates when at least one has scalar reductions of some of its
      components.  There are three possible scenarios: Both the LHS and RHS have