params.def (PARAM_MIN_CROSSJUMP_INSNS): New.

2004-08-06  Pat Haugen  <pthaugen@us.ibm.com>

        * params.def (PARAM_MIN_CROSSJUMP_INSNS): New.
        * cfgcleanup.c (try_crossjump_to_edge): Add minimum insn match
        threshhold.
        * doc/invoke.texi (param): Document min-crossjump-insns.

From-SVN: r85646

gcc/ChangeLog

+2004-08-06  Pat Haugen  <pthaugen@us.ibm.com>
+
+	* params.def (PARAM_MIN_CROSSJUMP_INSNS): New.
+	* cfgcleanup.c (try_crossjump_to_edge): Add minimum insn match
+	threshhold.
+	* doc/invoke.texi (param): Document min-crossjump-insns.
+
 2004-08-06  Richard Sandiford  <rsandifo@redhat.com>
 
 	PR c/13282

gcc/cfgcleanup.c

@@ -1507,7 +1507,13 @@ try_crossjump_to_edge (int mode, edge e1, edge e2)
 
   /* ... and part the second.  */
   nmatch = flow_find_cross_jump (mode, src1, src2, &newpos1, &newpos2);
-  if (!nmatch)
+
+  /* Don't proceed with the crossjump unless we found a sufficient number
+     of matching instructions or the 'from' block was totally matched
+     (such that its predecessors will hopefully be redirected and the
+     block removed).  */
+  if ((nmatch < PARAM_VALUE (PARAM_MIN_CROSSJUMP_INSNS))
+      && (newpos1 != BB_HEAD (src1)))
     return false;
 
 #ifndef CASE_DROPS_THROUGH

gcc/doc/invoke.texi

@@ -5094,6 +5094,12 @@ the number of edges incoming to each block.  Increasing values mean
 more aggressive optimization, making the compile time increase with
 probably small improvement in executable size.
 
+@item min-crossjump-insns
+The minimum number of instructions which must be matched at the end
+of two blocks before crossjumping will be performed on them.  This
+value is ignored in the case where all instructions in the block being
+crossjumped from are matched.  The default value is 5.
+
 @item max-delay-slot-insn-search
 The maximum number of instructions to consider when looking for an
 instruction to fill a delay slot.  If more than this arbitrary number of

gcc/params.def

@@ -306,6 +306,12 @@ DEFPARAM(PARAM_MAX_CROSSJUMP_EDGES,
 	 "The maximum number of incoming edges to consider for crossjumping",
 	 100)
 
+/* The minimum number of matching instructions to consider for crossjumping.  */
+DEFPARAM(PARAM_MIN_CROSSJUMP_INSNS,
+     "min-crossjump-insns",
+     "The minimum number of matching instructions to consider for crossjumping",
+     5)
+
 /* The maximum length of path considered in cse.  */
 DEFPARAM(PARAM_MAX_CSE_PATH_LENGTH,
 	 "max-cse-path-length",