expr.c [...]: New macro defining the maximum number of move instructions to use when...

	* expr.c [CLEAR_RATIO]: New macro defining the maximum number
	of move instructions to use when clearing memory, c.f. MOVE_RATIO.
	[CLEAR_BY_PIECES]: New macro, using CLEAR_RATIO, to determine
	whether clear_by_pieces should be used to clear storage.
	(clear_storage): Use CLEAR_BY_PIECES instead of MOVE_BY_PIECES.

	* doc/tm.texi: Document these two new target macros.

From-SVN: r55429

1 files changed, 20 insertions, 1 deletions

diff --git a/gcc/expr.c b/gcc/expr.c
index 779bf87..870a4c5 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -192,6 +192,25 @@ static bool float_extend_from_mem[NUM_MACHINE_MODES][NUM_MACHINE_MODES];
   (move_by_pieces_ninsns (SIZE, ALIGN) < (unsigned int) MOVE_RATIO)
 #endif
 
+/* If a clear memory operation would take CLEAR_RATIO or more simple
+   move-instruction sequences, we will do a clrstr or libcall instead.  */
+
+#ifndef CLEAR_RATIO
+#if defined (HAVE_clrstrqi) || defined (HAVE_clrstrhi) || defined (HAVE_clrstrsi) || defined (HAVE_clrstrdi) || defined (HAVE_clrstrti)
+#define CLEAR_RATIO 2
+#else
+/* If we are optimizing for space, cut down the default clear ratio.  */
+#define CLEAR_RATIO (optimize_size ? 3 : 15)
+#endif
+#endif
+
+/* This macro is used to determine whether clear_by_pieces should be
+   called to clear storage.  */
+#ifndef CLEAR_BY_PIECES_P
+#define CLEAR_BY_PIECES_P(SIZE, ALIGN) \
+  (move_by_pieces_ninsns (SIZE, ALIGN) < (unsigned int) CLEAR_RATIO)
+#endif
+
 /* This array records the insn_code of insns to perform block moves.  */
 enum insn_code movstr_optab[NUM_MACHINE_MODES];
 
@@ -2633,7 +2652,7 @@ clear_storage (object, size)
       size = protect_from_queue (size, 0);
 
       if (GET_CODE (size) == CONST_INT
-	  && MOVE_BY_PIECES_P (INTVAL (size), align))
+	  && CLEAR_BY_PIECES_P (INTVAL (size), align))
 	clear_by_pieces (object, INTVAL (size), align);
       else
 	{