re PR rtl-optimization/60651 (Mode switching instructions are sometimes emitted in the wrong order)

gcc:
        PR rtl-optimization/60651
        * mode-switching.c (optimize_mode_switching): Make sure to emit
        sets of a lower numbered entity before sets of a higher numbered
        entity to a mode of the same or lower priority.
        When creating a seginfo for a basic block that starts with a code
        label, move the insertion point past the code label.
        (new_seginfo): Document and enforce requirement that
        NOTE_INSN_BASIC_BLOCK only appears for empty blocks.
        * doc/tm.texi.in: Document ordering constraint for emitted mode sets.
        * doc/tm.texi: Regenerate.
gcc/testsuite:
        PR rtl-optimization/60651
        * gcc.target/epiphany/mode-switch.c: New test.

From-SVN: r209312

5 files changed, 45 insertions, 3 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6d99d17..32ed05f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+2014-04-11  Joern Rennecke  <joern.rennecke@embecosm.com>
+
+	PR rtl-optimization/60651
+	* mode-switching.c (optimize_mode_switching): Make sure to emit
+	sets of a lower numbered entity before sets of a higher numbered
+	entity to a mode of the same or lower priority.
+	When creating a seginfo for a basic block that starts with a code
+	label, move the insertion point past the code label.
+	(new_seginfo): Document and enforce requirement that
+	NOTE_INSN_BASIC_BLOCK only appears for empty blocks.
+	* doc/tm.texi.in: Document ordering constraint for emitted mode sets.
+	* doc/tm.texi: Regenerate.
+
 2014-01-11  Joern Rennecke  <joern.rennecke@embecosm.com>
 
 	PR target/60811
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index f7024a7..b8ca17e 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -9778,6 +9778,8 @@ for @var{entity}.  For any fixed @var{entity}, @code{mode_priority_to_mode}
 Generate one or more insns to set @var{entity} to @var{mode}.
 @var{hard_reg_live} is the set of hard registers live at the point where
 the insn(s) are to be inserted.
+Sets of a lower numbered entity will be emitted before sets of a higher
+numbered entity to a mode of the same or lower priority.
 @end defmac
 
 @node Target Attributes
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 6dcbde4..d793d26 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -7447,6 +7447,8 @@ for @var{entity}.  For any fixed @var{entity}, @code{mode_priority_to_mode}
 Generate one or more insns to set @var{entity} to @var{mode}.
 @var{hard_reg_live} is the set of hard registers live at the point where
 the insn(s) are to be inserted.
+Sets of a lower numbered entity will be emitted before sets of a higher
+numbered entity to a mode of the same or lower priority.
 @end defmac
 
 @node Target Attributes
diff --git a/gcc/mode-switching.c b/gcc/mode-switching.c
index 3166539..2848da3 100644
--- a/gcc/mode-switching.c
+++ b/gcc/mode-switching.c
@@ -96,12 +96,18 @@ static void make_preds_opaque (basic_block, int);
 
 
 /* This function will allocate a new BBINFO structure, initialized
-   with the MODE, INSN, and basic block BB parameters.  */
+   with the MODE, INSN, and basic block BB parameters.
+   INSN may not be a NOTE_INSN_BASIC_BLOCK, unless it is an empty
+   basic block; that allows us later to insert instructions in a FIFO-like
+   manner.  */
 
 static struct seginfo *
 new_seginfo (int mode, rtx insn, int bb, HARD_REG_SET regs_live)
 {
   struct seginfo *ptr;
+
+  gcc_assert (!NOTE_INSN_BASIC_BLOCK_P (insn)
+	      || insn == BB_END (NOTE_BASIC_BLOCK (insn)));
   ptr = XNEW (struct seginfo);
   ptr->mode = mode;
   ptr->insn_ptr = insn;
@@ -534,7 +540,13 @@ optimize_mode_switching (void)
 		break;
 	    if (e)
 	      {
-		ptr = new_seginfo (no_mode, BB_HEAD (bb), bb->index, live_now);
+		rtx ins_pos = BB_HEAD (bb);
+		if (LABEL_P (ins_pos))
+		  ins_pos = NEXT_INSN (ins_pos);
+		gcc_assert (NOTE_INSN_BASIC_BLOCK_P (ins_pos));
+		if (ins_pos != BB_END (bb))
+		  ins_pos = NEXT_INSN (ins_pos);
+		ptr = new_seginfo (no_mode, ins_pos, bb->index, live_now);
 		add_seginfo (info + bb->index, ptr);
 		bitmap_clear_bit (transp[bb->index], j);
 	      }
@@ -733,7 +745,15 @@ optimize_mode_switching (void)
 		    {
 		      emitted = true;
 		      if (NOTE_INSN_BASIC_BLOCK_P (ptr->insn_ptr))
-			emit_insn_after (mode_set, ptr->insn_ptr);
+			/* We need to emit the insns in a FIFO-like manner,
+			   i.e. the first to be emitted at our insertion
+			   point ends up first in the instruction steam.
+			   Because we made sure that NOTE_INSN_BASIC_BLOCK is
+			   only used for initially empty basic blocks, we
+			   can archive this by appending at the end of
+			   the block.  */
+			emit_insn_after
+			  (mode_set, BB_END (NOTE_BASIC_BLOCK (ptr->insn_ptr)));
 		      else
 			emit_insn_before (mode_set, ptr->insn_ptr);
 		    }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index fdacc9c..e7f800a 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2014-04-11  Joern Rennecke  <joern.rennecke@embecosm.com>
+
+	PR rtl-optimization/60651
+	* gcc.target/epiphany/mode-switch.c: New test.
+
 2014-04-11  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/58600