------- Additional Comments From steven at gcc dot gnu dot org 2005-09-18
15:59 -------
Actually fold_stmt has nothing to do with it. It is fold (cached_lhs) in
trhead_across_edge that is the problem here. Jeff, what do you think about
this patch?
Index: tree-ssa-dom.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-ssa-dom.c,v
retrieving revision 2.127
diff -u -3 -p -r2.127 tree-ssa-dom.c
--- tree-ssa-dom.c 2 Aug 2005 00:12:39 -0000 2.127
+++ tree-ssa-dom.c 18 Sep 2005 15:57:22 -0000
@@ -701,7 +701,7 @@ thread_across_edge (struct dom_walk_data
else
{
/* Copy the operands. */
- tree *copy;
+ tree *copy, prefold_lhs;
ssa_op_iter iter;
use_operand_p use_p;
unsigned int num, i = 0;
@@ -725,12 +725,33 @@ thread_across_edge (struct dom_walk_data
/* Try to fold/lookup the new expression. Inserting the
expression into the hash table is unlikely to help
- simplify anything later, so just query the hashtable. */
- cached_lhs = fold (TREE_OPERAND (stmt, 1));
- if (TREE_CODE (cached_lhs) != SSA_NAME
- && !is_gimple_min_invariant (cached_lhs))
- cached_lhs = lookup_avail_expr (stmt, false);
+ simplify anything later, so just query the hashtable.
+ Sadly, we have to handle conditional assignments specially
+ here, because fold expects all the operands of an expression
+ to be folded before the expression itself is folded, but we
+ can't just substitute the folded condition here. */
+ if (TREE_CODE (TREE_OPERAND (stmt, 1)) == COND_EXPR)
+ {
+ tree cond = COND_EXPR_COND (TREE_OPERAND (stmt, 1));
+ cond = fold (cond);
+ if (cond == boolean_true_node)
+ prefold_lhs = COND_EXPR_THEN (TREE_OPERAND (stmt, 1));
+ else if (cond == boolean_false_node)
+ prefold_lhs = COND_EXPR_ELSE (TREE_OPERAND (stmt, 1));
+ else
+ prefold_lhs = NULL;
+ }
+ else
+ prefold_lhs = TREE_OPERAND (stmt, 1);
+
+ if (prefold_lhs)
+ {
+ cached_lhs = fold (prefold_lhs);
+ if (TREE_CODE (cached_lhs) != SSA_NAME
+ && !is_gimple_min_invariant (cached_lhs))
+ cached_lhs = lookup_avail_expr (stmt, false);
+ }
/* Restore the statement's original uses/defs. */
i = 0;
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23049
