rtl-ssa: Fix thinko when adding live-out uses

While testing a later patch, I found that create_degenerate_phi
had an inverted test for bitmap_set_bit.  It was assuming that
the return value was the previous bit value, rather than a
"something changed" value. :(

Also, the call to add_live_out_use shouldn't be conditional
on the DF_LR_OUT operation, since the register could be live-out
because of uses later in the same EBB (which do not require a
live-out use to be added to the rtl-ssa instruction).  Instead,
add_live_out should itself check whether a live-out use already exists.

gcc/
	* rtl-ssa/blocks.cc (function_info::create_degenerate_phi): Fix
	inverted test of bitmap_set_bit.  Call add_live_out_use even
	if the register was previously live-out from the predecessor block.
	Instead...
	(function_info::add_live_out_use): ...check here whether a live-out
	use already exists.

diff --git a/gcc/rtl-ssa/blocks.cc b/gcc/rtl-ssa/blocks.cc
index 953fd9e516ed60e3970592c2bf9693fdc4c12132..a57b9e15f13cd6a394e60ec189bf0db160b9a6fd 100644 (file)
--- a/gcc/rtl-ssa/blocks.cc
+++ b/gcc/rtl-ssa/blocks.cc
@@ -315,15 +315,14 @@ function_info::add_live_out_use (bb_info *bb, set_info *def)
 
   // If the end of the block already has an artificial use, that use
   // acts to make DEF live at the appropriate point.
-  use_info *use = def->last_nondebug_insn_use ();
-  if (use && use->insn () == bb->end_insn ())
+  if (find_use (def, bb->end_insn ()).matching_use ())
     return;
 
   // Currently there is no need to maintain a backward link from the end
   // instruction to the list of live-out uses.  Such a list would be
   // expensive to update if it was represented using the usual insn_info
   // access arrays.
-  use = allocate<use_info> (bb->end_insn (), def->resource (), def);
+  auto *use = allocate<use_info> (bb->end_insn (), def->resource (), def);
   use->set_is_live_out_use (true);
   add_use (use);
 }
@@ -540,12 +539,12 @@ function_info::create_degenerate_phi (ebb_info *ebb, set_info *def)
       basic_block pred_cfg_bb = single_pred (ebb->first_bb ()->cfg_bb ());
       bb_info *pred_bb = this->bb (pred_cfg_bb);
 
-      if (!bitmap_set_bit (DF_LR_IN (ebb->first_bb ()->cfg_bb ()), regno))
+      if (bitmap_set_bit (DF_LR_IN (ebb->first_bb ()->cfg_bb ()), regno))
        {
          // The register was not previously live on entry to EBB and
          // might not have been live on exit from PRED_BB either.
-         if (bitmap_set_bit (DF_LR_OUT (pred_cfg_bb), regno))
-           add_live_out_use (pred_bb, def);
+         bitmap_set_bit (DF_LR_OUT (pred_cfg_bb), regno);
+         add_live_out_use (pred_bb, def);
        }
       else
        {