VN already sees if an expresion is fully constant so there's no reason
to duplicate that work during PHI translation. I've verified with
an assert the paths are indeed unreachable.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2017-11-17 Richard Biener <rguent...@suse.de>
* tree-ssa-pre.c (phi_translate_1): Remove redundant constant
folding of references.
Index: gcc/tree-ssa-pre.c
===================================================================
--- gcc/tree-ssa-pre.c (revision 254797)
+++ gcc/tree-ssa-pre.c (working copy)
@@ -1566,7 +1566,6 @@ phi_translate_1 (pre_expr expr, bitmap_s
if (changed || newvuse != vuse)
{
unsigned int new_val_id;
- pre_expr constant;
tree result = vn_reference_lookup_pieces (newvuse, ref->set,
ref->type,
@@ -1611,15 +1610,7 @@ phi_translate_1 (pre_expr expr, bitmap_s
expr->id = 0;
if (newref)
- {
- PRE_EXPR_REFERENCE (expr) = newref;
- constant = fully_constant_expression (expr);
- if (constant != expr)
- return constant;
-
- new_val_id = newref->value_id;
- get_or_alloc_expression_id (expr);
- }
+ new_val_id = newref->value_id;
else
{
if (changed || !same_valid)
@@ -1637,12 +1628,9 @@ phi_translate_1 (pre_expr expr, bitmap_s
newoperands,
result, new_val_id);
newoperands = vNULL;
- PRE_EXPR_REFERENCE (expr) = newref;
- constant = fully_constant_expression (expr);
- if (constant != expr)
- return constant;
- get_or_alloc_expression_id (expr);
}
+ PRE_EXPR_REFERENCE (expr) = newref;
+ get_or_alloc_expression_id (expr);
add_to_value (new_val_id, expr);
}
newoperands.release ();
