gcc/ChangeLog:

PR debug/41343
PR debug/41447
PR debug/41264
PR debug/41338
* tree.def (DEBUG_EXPR_DECL): New.
* rtl.def (DEBUG_EXPR): New.
* gengtype.c (adjust_field_rtx_def): Handle it.
* tree-ssa.c (propagate_var_def_into_debug_stmts): Rename to...
(insert_debug_temp_for_var_def): ... this.  Drop support for
moving.  Take iterator for def stmt; insert debug stmt before it.
Scan early for use count and kind in debug stmts.
(propagate_defs_into_debug_stmts): Rename to...
(insert_debug_temps_for_defs): ... this.  Likewise.
* tree.h (DEBUG_TEMP_UID): New.
* tree.c (next_debug_decl_uid): New.
(make_node_stat): Count debug decls separately.
(copy_node_stat): Likewise.
* cfgexpand.c (expand_debug_expr): Handle DEBUG_EXPR_DECL.
* var-tracking.c (dv_is_decl_p): Recognize it.
(VALUE_RECURSED_INTO): Apply to DEBUG_EXPRs too.
(track_expr_p): Track expanded DEBUG_EXPR_DECLs.
(vt_expand_loc_callback): Expand DEBUG_EXPRs.
(emit_note_insn_var_location): Don't emit notes for DEBUG_EXPR_DECLs.
* cselib.c (rtx_equal_for_cselib_p): Handle DEBUG_EXPR.
(cselib_hash_rtx): Likewise.
(cselib_expand_value_rtx_1): Use callback for DEBUG_EXPR.
* tree-ssa-operands.c (get_expr_operands): Skip DEBUG_EXPR_DECLs in
debug bind stmts.
* emit-rtl.c (verify_rtx_sharing): Handle DEBUG_EXPR and VALUE.
(copy_rtx_if_shared_1, reset_used_flags, set_used_flags): Likewise.
* rtl.c (copy_rtx): Likewise.
(rtx_equal_p_cb, rtx_equal_p): Handle DEBUG_EXPR.
* print-rtl.c (print_rtx): Likewise.
* sched-vis.c (print_value): Likewise.
(print_insn): Handle DEBUG_EXPR_DECL.
* tree-dump.c (dequeue_and_dump): Likewise.
* tree-pretty-print.c (dump_decl_name, dump_generic_node): Likewise.
* gimple-iterator (gsi_replace): Check for same lhs.
(gsi_remove): Insert debug temps.
* tree-ssa-loop-im.c (rewrite_reciprocal): Replace with same lhs.
(move_computations_stmt): Drop explicit propagation into debug stmts.
(rewrite_bittest): Likewise.  Use gsi_remove for propagation.
* tree-ssa-reassoc.c (rewrite_expr_tree, linearize_expr): Likewise.
* tree-ssa-sink.c (statement_sink_location): Likewise.
* tree-ssa-forwprop (forward_propagate_addr_expr): Likewise.
* tree-ssanames.c (release_ssa_name): Adjust for rename.
* tree-flow.h: Likewise.
* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Don't mark
debug temps without values.
(eliminate_unnecessary_stmts): Don't discard just-inserted
debug stmts.
gcc/testsuite/ChangeLog:
PR debug/41343
PR debug/41447
PR debug/41264
PR debug/41338
* gcc.dg/guality/pr41447-1.c: New.
* gcc.dg/debug/pr41264-1.c: New.
* gcc.dg/debug/pr41343-1.c: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@152681 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 12 insertions, 14 deletions

diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index 67d0472cc59..7dd07c1ca2c 100644
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -325,7 +325,13 @@ mark_stmt_if_obviously_necessary (gimple stmt, bool aggressive)
       break;
 
     case GIMPLE_DEBUG:
-      mark_stmt_necessary (stmt, false);
+      /* Debug temps without a value are not useful.  ??? If we could
+	 easily locate the debug temp bind stmt for a use thereof,
+	 would could refrain from marking all debug temps here, and
+	 mark them only if they're used.  */
+      if (gimple_debug_bind_has_value_p (stmt)
+	  || TREE_CODE (gimple_debug_bind_get_var (stmt)) != DEBUG_EXPR_DECL)
+	mark_stmt_necessary (stmt, false);
       return;
 
     case GIMPLE_GOTO:
@@ -1071,7 +1077,7 @@ eliminate_unnecessary_stmts (void)
 {
   bool something_changed = false;
   basic_block bb;
-  gimple_stmt_iterator gsi;
+  gimple_stmt_iterator gsi, psi;
   gimple stmt;
   tree call;
   VEC (basic_block, heap) *h;
@@ -1111,10 +1117,13 @@ eliminate_unnecessary_stmts (void)
       bb = VEC_pop (basic_block, h);
 
       /* Remove dead statements.  */
-      for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
+      for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi = psi)
 	{
 	  stmt = gsi_stmt (gsi);
 
+	  psi = gsi;
+	  gsi_prev (&psi);
+
 	  stats.total++;
 
 	  /* If GSI is not necessary then remove it.  */
@@ -1122,14 +1131,6 @@ eliminate_unnecessary_stmts (void)
 	    {
 	      remove_dead_stmt (&gsi, bb);
 	      something_changed = true;
-
-	      /* If stmt was the last stmt in the block, we want to
-		 move gsi to the stmt that became the last stmt, but
-		 gsi_prev would crash.  */
-	      if (gsi_end_p (gsi))
-		gsi = gsi_last_bb (bb);
-	      else
-		gsi_prev (&gsi);
 	    }
 	  else if (is_gimple_call (stmt))
 	    {
@@ -1159,10 +1160,7 @@ eliminate_unnecessary_stmts (void)
 		    }
 		  notice_special_calls (stmt);
 		}
-	      gsi_prev (&gsi);
 	    }
-	  else
-	    gsi_prev (&gsi);
 	}
     }