This patch just teaches DOM that ARRAY_REFs can be equivalent to MEM_REFs (with
pointer type to the array element type).
gcc/ChangeLog:
* tree-ssa-dom.c (dom_normalize_single_rhs): New.
(dom_normalize_gimple_stmt): New.
(lookup_avail_expr): Call dom_normalize_gimple_stmt.
---
gcc/tree-ssa-dom.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 67 insertions(+), 1 deletion(-)
diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index 38cceff..fca8a80 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -1897,6 +1897,72 @@ vuse_eq (ao_ref *, tree vuse1, unsigned int cnt, void
*data)
return NULL;
}
+/* Return the normal form of EXPR, the gimple_assign_rhs1 of a
GIMPLE_SINGLE_RHS
+ assignment, or NULL_TREE if EXPR is already in normal form.
+ The normal form is such that if two expressions normalize to trees that are
+ operand_equal_p, then dominator optimizations can replace one by the value
+ produced by the other.
+ It is not necessary that expressions with equal canonical forms are
+ equivalent in all other situations, e.g. aliasing. */
+
+static tree
+dom_normalize_single_rhs (tree expr)
+{
+ switch (TREE_CODE (expr))
+ {
+ case ARRAY_REF:
+ {
+ tree index = TREE_OPERAND (expr, 1);
+ tree low_bound = array_ref_low_bound (expr);
+ if (!TREE_CONSTANT (index) || !TREE_CONSTANT (low_bound))
+ return NULL_TREE;
+
+ if (! integer_zerop (low_bound))
+ index = fold_build2 (MINUS_EXPR, TREE_TYPE (index), index, low_bound);
+
+ tree esz = array_ref_element_size (expr);
+ gcc_assert (TREE_CONSTANT (esz));
+ tree offset = fold_build2 (MULT_EXPR, sizetype, index, esz);
+
+ offset = fold_convert (build_pointer_type (TREE_TYPE (expr)), offset);
+
+ tree base = TREE_OPERAND (expr, 0);
+ base = build_fold_addr_expr (base);
+
+ return fold_build2 (MEM_REF, TREE_TYPE (expr), base, offset);
+ }
+ default:
+ return NULL_TREE;
+ }
+}
+
+/* Return the normal form of STMT, or STMT if it is already normalized. */
+
+static gimple *
+dom_normalize_gimple_stmt (gimple *stmt)
+{
+ if (gimple_code (stmt) == GIMPLE_ASSIGN)
+ {
+ enum tree_code rhs_code = gimple_assign_rhs_code (stmt);
+ if (get_gimple_rhs_class (rhs_code) == GIMPLE_SINGLE_RHS)
+ if (tree nrhs = dom_normalize_single_rhs (gimple_assign_rhs1 (stmt)))
+ {
+ tree lhs = gimple_assign_lhs (stmt);
+ /* Exchanged statements, which are never part of the CFG,
+ can have invalid LHS. */
+ gimple *defstmt = 0;
+ if (TREE_CODE (lhs) == SSA_NAME)
+ defstmt = SSA_NAME_DEF_STMT (lhs);
+ gassign *new_stmt = gimple_build_assign (lhs, nrhs);
+ if (TREE_CODE (lhs) == SSA_NAME)
+ SSA_NAME_DEF_STMT (lhs) = defstmt;
+ gimple_set_vuse (new_stmt, gimple_vuse (stmt));
+ return new_stmt;
+ }
+ }
+ return stmt;
+}
+
/* Search for an existing instance of STMT in the AVAIL_EXPRS_STACK table.
If found, return its LHS. Otherwise insert STMT in the table and
return NULL_TREE.
@@ -1918,7 +1984,7 @@ lookup_avail_expr (gimple *stmt, bool insert,
else
lhs = gimple_get_lhs (stmt);
- class expr_hash_elt element (stmt, lhs);
+ class expr_hash_elt element (dom_normalize_gimple_stmt (stmt), lhs);
if (dump_file && (dump_flags & TDF_DETAILS))
{
--
1.9.1
