[PATCH][match-and-simplify] Properly simplify before failing with !seq

[Richard Biener]

This makes sure we simplify an expression before giving up because
the caller only expects a singleton result.  Otherwise patterns like

(match_and_simplify
  (plus @0 integer_zerop)
  @0)

(match_and_simplify
  (plus (plus @0 INTEGER_CST_P@1) INTEGER_CST_P@2)
  (plus @0 (plus @1 @2)))

that expect to constant-fold (plus @1 @2) and the resulting
(plus @0 0) for (a + 1) + -1 won't match when called with !seq
(as for example SCCVN does).

Bootstrapped and tested on x86_64-unknown-linux-gnu and applied.

Richard.

2014-03-13  Richard Biener  <rguent...@suse.de>

        * genmatch.c (expr::gen_gimple_transform): Make sure to
        try simplifying a transform pattern even when seq is NULL
        as seq may not be needed.

Index: gcc/genmatch.c
===================================================================
--- gcc/genmatch.c      (revision 208478)
+++ gcc/genmatch.c      (working copy)
@@ -332,20 +332,32 @@ void
 expr::gen_gimple_transform (FILE *f, const char *label)
 {
   fprintf (f, "({\n");
-  fprintf (f, "  if (!seq) ");
-  gen_gimple_match_fail (f, label);
-  fprintf (f, "  tree ops[%d];\n", ops.length ());
+  fprintf (f, "  tree ops[%d], res;\n", ops.length ());
   for (unsigned i = 0; i < ops.length (); ++i)
     {
-      fprintf (f, "   ops[%u] = ", i);
+      fprintf (f, "  ops[%u] = ", i);
       ops[i]->gen_gimple_transform (f, label);
       fprintf (f, ";\n");
     }
-  fprintf (f, "  gimple_build (seq, UNKNOWN_LOCATION, %s, TREE_TYPE (ops[0])",
+  /* ???  Have another helper that is like gimple_build but may
+     fail if seq == NULL.  */
+  fprintf (f, "  if (!seq)\n"
+          "    {\n"
+          "      res = gimple_match_and_simplify (%s, TREE_TYPE (ops[0])",
           operation->op->id);
   for (unsigned i = 0; i < ops.length (); ++i)
     fprintf (f, ", ops[%u]", i);
+  fprintf (f, ", seq, valueize);\n");
+  fprintf (f, "      if (!res) ");
+  gen_gimple_match_fail (f, label);
+  fprintf (f, "    }\n");
+  fprintf (f, "  else\n");
+  fprintf (f, "    res = gimple_build (seq, UNKNOWN_LOCATION, %s, "
+          "TREE_TYPE (ops[0])", operation->op->id);
+  for (unsigned i = 0; i < ops.length (); ++i)
+    fprintf (f, ", ops[%u]", i);
   fprintf (f, ", valueize);\n");
+  fprintf (f, "  res;\n");
   fprintf (f, "})");
 }