s390.h (MOVE_RATIO): Define new target macro.

2008-01-24  Andreas Krebbel  <krebbel1@de.ibm.com>

	* config/s390/s390.h (MOVE_RATIO): Define new target macro.

From-SVN: r131799

gcc/ChangeLog

+2008-01-24  Andreas Krebbel  <krebbel1@de.ibm.com>
+
+	* config/s390/s390.h (MOVE_RATIO): Define new target macro.
+
 2008-01-24  Richard Sandiford  <rsandifo@nildram.co.uk>
 
 	PR tree-optimization/34472

gcc/config/s390/s390.h

@@ -815,6 +815,16 @@ extern struct rtx_def *s390_compare_op0, *s390_compare_op1, *s390_compare_emitte
 /* Don't perform CSE on function addresses.  */
 #define NO_FUNCTION_CSE
 
+/* This value is used in tree-sra to decide whether it might benefical
+   to split a struct move into several word-size moves.  For S/390
+   only small values make sense here since struct moves are relatively
+   cheap thanks to mvc so the small default value choosen for archs
+   with memmove patterns should be ok.  But this value is multiplied
+   in tree-sra with UNITS_PER_WORD to make a decision so we adjust it
+   here to compensate for that factor since mvc costs exactly the same
+   on 31 and 64 bit.  */
+#define MOVE_RATIO (TARGET_64BIT? 2 : 4)
+
 
 /* Sections.  */