[PATCH] Speedup lookup_constraint for 2-letter constraints

[Richard Biener]

This speeds up lookup_constraint by allowing the generic folding
for n == 1 strncmp calls to trigger, handling two-letter constraints
by two char comparisons instead of one and a call to strncmp (which
ends up not being inlined because it's considered cold ...).

Bootstrap & regtest pending on x86_64-unknown-linux-gnu.

Ok?

Thanks,
Richard.
2013-02-19  Richard Biener  <rguenther@suse.de>

	* genpreds.c (write_lookup_constraint): Do not compare first
	letter of the constraint again.

Index: gcc/genpreds.c
===================================================================
--- gcc/genpreds.c	(revision 196134)
+++ gcc/genpreds.c	(working copy)
@@ -945,9 +945,10 @@ write_lookup_constraint (void)
 	{
 	  do
 	    {
-	      printf ("      if (!strncmp (str, \"%s\", %lu))\n"
+	      printf ("      if (!strncmp (str + 1, \"%s\", %lu))\n"
 		      "        return CONSTRAINT_%s;\n",
-		      c->name, (unsigned long int) c->namelen, c->c_name);
+		      c->name + 1, (unsigned long int) c->namelen - 1,
+		      c->c_name);
 	      c = c->next_this_letter;
 	    }
 	  while (c);