re PR debug/53740 (--enable-checking=yes,rtl bootstrap failure with ada)

PR debug/53740
PR debug/52983
PR debug/48866
* dce.c (word_dce_process_block): Check whether inserting debug
temps are needed even for needed insns.
(dce_process_block): Likewise.
* df-problems.c (dead_debug_add): Add comment about multi-regs.
(dead_debug_insert_temp): Likewise.  Don't subreg when we're
setting fewer regs than a multi-reg requires.

From-SVN: r189036

1 files changed, 10 insertions, 4 deletions

diff --git a/gcc/dce.c b/gcc/dce.c
index 8954d5c..2e58e43 100644
--- a/gcc/dce.c
+++ b/gcc/dce.c
@@ -864,9 +864,12 @@ word_dce_process_block (basic_block bb, bool redo_out)
 	   anything in local_live.  */
 	if (marked_insn_p (insn))
 	  df_word_lr_simulate_uses (insn, local_live);
+
 	/* Insert debug temps for dead REGs used in subsequent debug
-	   insns.  */
-	else if (debug.used && !bitmap_empty_p (debug.used))
+	   insns.  We may have to emit a debug temp even if the insn
+	   was marked, in case the debug use was after the point of
+	   death.  */
+	if (debug.used && !bitmap_empty_p (debug.used))
 	  {
 	    df_ref *def_rec;
 
@@ -963,9 +966,12 @@ dce_process_block (basic_block bb, bool redo_out, bitmap au)
 	   anything in local_live.  */
 	if (needed)
 	  df_simulate_uses (insn, local_live);
+
 	/* Insert debug temps for dead REGs used in subsequent debug
-	   insns.  */
-	else if (debug.used && !bitmap_empty_p (debug.used))
+	   insns.  We may have to emit a debug temp even if the insn
+	   was marked, in case the debug use was after the point of
+	   death.  */
+	if (debug.used && !bitmap_empty_p (debug.used))
 	  for (def_rec = DF_INSN_DEFS (insn); *def_rec; def_rec++)
 	    dead_debug_insert_temp (&debug, DF_REF_REGNO (*def_rec), insn,
 				    DEBUG_TEMP_BEFORE_WITH_VALUE);