https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113433
Jeffrey A. Law <law at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |law at gcc dot gnu.org
--- Comment #2 from Jeffrey A. Law <law at gcc dot gnu.org> ---
So we could attack this as a DOM problem. Not all the infrastructure is in
there. But the recognition of negated expressions isn't hard. Something like
this in tree-ssa-scopedtables will detect the negated expression in the hash
table.
/* We might be able to lookup the negated expression. */
case PLUS_EXPR:
{
tree x = gimple_assign_rhs_to_tree (stmt);
x = fold_unary (NEGATE_EXPR, TREE_TYPE (x), x);
struct hashable_expr expr;
expr.type = TREE_TYPE (x);
expr.kind = EXPR_BINARY;
expr.ops.binary.op = MINUS_EXPR;
expr.ops.binary.opnd0 = TREE_OPERAND (x, 0);
expr.ops.binary.opnd1 = TREE_OPERAND (x, 1);
class expr_hash_elt element2 (&expr, NULL_TREE);
expr_hash_elt **slot
= m_avail_exprs->find_slot (&element2, NO_INSERT);
if (slot && *slot)
return fold_build1 (NEGATE_EXPR, TREE_TYPE (x), (*slot)->lhs
());
return NULL_TREE;
}
Right now DOM isn't prepared for avail_expr_stack::simplify_binary_operation to
return anything other than a constant, ssa_name or NULL. But how hard could it
be to expand further :-)
Not sure if this happens enough to make the extra lookups worth the effort.
