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[patch] tree-cfg.c: Teach find_taken_edge to reject VAL being NULL.


Attached is a patch to teach find_taken_edge to reject VAL being NULL.

All callers of find_taken_edge except visit_cond_stmt calls it with
nonzero VAL, so the null checks of VAL are partially redundant.

We always keep COND_EXPR and SWITCH_EXPR "interesting" by removing
degerates forms like those with only one outgoing edge, so it doesn't
make sense to ask find_taken_edge to find the taken edge with no hint,
that is, VAL being NULL.

The patch removes the null checks while having visit_cond_stmt check
its VAL before calling find_taken_edge.

Tested on i686-pc-linux-gnu.  OK to apply?

Kazu Hirata

2004-11-04  Kazu Hirata  <>

	* tree-cfg.c (find_taken_edge): Reject VAL begin NULL.
	* tree-ssa-ccp.c (visit_cond_stmt): Don't call find_taken_edge
	with VAL being NULL.

Index: tree-cfg.c
RCS file: /cvs/gcc/gcc/gcc/tree-cfg.c,v
retrieving revision 2.98
diff -u -d -p -r2.98 tree-cfg.c
--- tree-cfg.c	3 Nov 2004 01:40:56 -0000	2.98
+++ tree-cfg.c	3 Nov 2004 02:33:55 -0000
@@ -1954,15 +1954,16 @@ find_taken_edge (basic_block bb, tree va
   gcc_assert (stmt);
   gcc_assert (is_ctrl_stmt (stmt));
+  gcc_assert (val);
   /* If VAL is a predicate of the form N RELOP N, where N is an
      SSA_NAME, we can usually determine its truth value.  */
-  if (val && COMPARISON_CLASS_P (val))
+  if (COMPARISON_CLASS_P (val))
     val = fold (val);
   /* If VAL is not a constant, we can't determine which edge might
      be taken.  */
-  if (val == NULL || !really_constant_p (val))
+  if (!really_constant_p (val))
     return NULL;
   if (TREE_CODE (stmt) == COND_EXPR)
Index: tree-ssa-ccp.c
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-ccp.c,v
retrieving revision 2.48
diff -u -d -p -r2.48 tree-ssa-ccp.c
--- tree-ssa-ccp.c	27 Oct 2004 17:45:20 -0000	2.48
+++ tree-ssa-ccp.c	3 Nov 2004 02:33:56 -0000
@@ -1123,7 +1123,7 @@ visit_cond_stmt (tree stmt, edge *taken_
      to the worklist.  If no single edge can be determined statically,
      return SSA_PROP_VARYING to feed all the outgoing edges to the
      propagation engine.  */
-  *taken_edge_p = find_taken_edge (block, val.const_val);
+  *taken_edge_p = val.const_val ? find_taken_edge (block, val.const_val) : 0;
   if (*taken_edge_p)

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