PR rtl-optimization/51933
* ree.c (transform_ifelse): Return true right away if dstreg is
already wider or equal to cand->mode.
(enum ext_modified_kind, struct ext_modified, ext_state): New types.
(make_defs_and_copies_lists): Remove defs_list and copies_list
arguments, add state argument, just truncate state->work_list
instead of always allocating and freeing the vector. Assert that
get_defs succeeds instead of returning 2. Changed return type to
bool.
(merge_def_and_ext): Add state argument. If SET_DEST doesn't
have ext_src_mode, see if it has been modified already with the
right kind of extension and has been extended before from the
ext_src_mode. If SET_DEST is already wider or equal to cand->mode,
just return true. Remember the original mode in state->modified
array.
(combine_reaching_defs): Add state argument. Don't allocate and
free here def_list, copied_list and vec vectors, instead just
VEC_truncate the vectors in *state. Don't handle outcome == 2
here.
(find_and_remove_re): Set DF_DEFER_INSN_RESCAN df flag.
Add state variable, clear vectors in it, initialize state.modified
if needed. Free all the vectors at the end and state.modified too.
Don't skip a candidate if the extension expression has been modified.
* gcc.c-torture/execute/pr51933.c: New test.
From-SVN: r183416
