This PR shows that array_ref_element_size may apply spurious casts which
in turn end up confusing VN/PRE.
Fixed as follows, bootstrapped on x86_64-unknown-linux-gnu, testing in
progress.
Richard.
2016-07-15 Richard Biener <rguent...@suse.de>
PR tree-optimization/71893
* tree-ssa-pre.c (create_component_ref_by_pieces_1): Compensate
for sizetype cast added by array_ref_element_size.
* tree-ssa-sccvn.c (copy_reference_ops_from_ref): Likewise.
Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c (revision 238370)
--- gcc/tree-ssa-pre.c (working copy)
*************** create_component_ref_by_pieces_1 (basic_
*** 2576,2581 ****
--- 2587,2595 ----
{
genop3 = size_binop (EXACT_DIV_EXPR, genop3,
size_int (TYPE_ALIGN_UNIT (elmt_type)));
+ /* We may have a useless conversion added by
+ array_ref_element_size via copy_reference_opts_from_ref. */
+ STRIP_USELESS_TYPE_CONVERSION (genop3);
genop3 = find_or_generate_expression (block, genop3, stmts);
if (!genop3)
return NULL_TREE;
Index: gcc/tree-ssa-sccvn.c
===================================================================
*** gcc/tree-ssa-sccvn.c (revision 238370)
--- gcc/tree-ssa-sccvn.c (working copy)
*************** copy_reference_ops_from_ref (tree ref, v
*** 810,815 ****
--- 810,818 ----
/* Always record lower bounds and element size. */
temp.op1 = array_ref_low_bound (ref);
temp.op2 = array_ref_element_size (ref);
+ /* array_ref_element_size forces the result to sizetype
+ even if that is the same as bitsizetype. */
+ STRIP_USELESS_TYPE_CONVERSION (temp.op2);
if (TREE_CODE (temp.op0) == INTEGER_CST
&& TREE_CODE (temp.op1) == INTEGER_CST
&& TREE_CODE (temp.op2) == INTEGER_CST)
