On Wed, Jun 24, 2020 at 9:21 AM Martin Liška <mli...@suse.cz> wrote:
>
> Hi.
>
> When expanding a VEC_COND_EXPR it happens that first argument (a SSA_NAME)
> that can be no longer used. When that happens we need to remove the SSA_NAME,
> otherwise we end up expanding it and for targets like s390x, there's no optab
> expansion. We need to remove them at both places as -O0 does not help us
> with a dead SSA_NAMEs after vector lowering.
>
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
> Cross-compiler for s390x was tested as well for problematic test-case.
>
> Ready to be installed?
Hmm, can you instead use simple_dce_from_worklist and simply
record all SSA_NAMEs you end up "forwarding" as possibly dead
in a bitmap? At least that hashmap traversal looks dangerous
with respect to address-space randomization and gsi_remove
inserting debug stmts and thus eventually allocating debug decls.
Thanks,
Richard.
> Thanks,
> Martin
>
> gcc/ChangeLog:
>
> PR tree-optimization/95745
> PR middle-end/95830
> * gimple-isel.cc (gimple_expand_vec_cond_exprs): Delete dead
> SSA_NAMEs used as the first argument of a VEC_COND_EXPR. Always
> return 0.
> * tree-vect-generic.c (expand_vector_condition): Remove dead
> SSA_NAMEs used as the firs argument of a VEC_COND_EXPR.
> ---
> gcc/gimple-isel.cc | 11 +++++++++--
> gcc/tree-vect-generic.c | 9 ++++++++-
> 2 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/gimple-isel.cc b/gcc/gimple-isel.cc
> index 97f92080503..25b893224af 100644
> --- a/gcc/gimple-isel.cc
> +++ b/gcc/gimple-isel.cc
> @@ -178,7 +178,6 @@ gimple_expand_vec_cond_exprs (void)
> {
> gimple_stmt_iterator gsi;
> basic_block bb;
> - bool cfg_changed = false;
> hash_map<tree, unsigned int> vec_cond_ssa_name_uses;
>
> FOR_EACH_BB_FN (bb, cfun)
> @@ -196,7 +195,15 @@ gimple_expand_vec_cond_exprs (void)
> }
> }
>
> - return cfg_changed ? TODO_cleanup_cfg : 0;
> + for (hash_map<tree, unsigned int>::iterator it =
> vec_cond_ssa_name_uses.begin ();
> + it != vec_cond_ssa_name_uses.end (); ++it)
> + if (num_imm_uses ((*it).first) == 0)
> + {
> + gsi = gsi_for_stmt (SSA_NAME_DEF_STMT ((*it).first));
> + gsi_remove (&gsi, true);
> + }
> +
> + return 0;
> }
>
> namespace {
> diff --git a/gcc/tree-vect-generic.c b/gcc/tree-vect-generic.c
> index 83d399a7898..2479368743d 100644
> --- a/gcc/tree-vect-generic.c
> +++ b/gcc/tree-vect-generic.c
> @@ -954,10 +954,11 @@ expand_vector_condition (gimple_stmt_iterator *gsi)
> tree comp_index = index;
> location_t loc = gimple_location (gsi_stmt (*gsi));
> tree_code code = TREE_CODE (a);
> + gassign *assign = NULL;
>
> if (code == SSA_NAME)
> {
> - gassign *assign = dyn_cast<gassign *> (SSA_NAME_DEF_STMT (a));
> + assign = dyn_cast<gassign *> (SSA_NAME_DEF_STMT (a));
> if (assign != NULL
> && TREE_CODE_CLASS (gimple_assign_rhs_code (assign)) ==
> tcc_comparison)
> {
> @@ -1064,6 +1065,12 @@ expand_vector_condition (gimple_stmt_iterator *gsi)
> constr = build_constructor (type, v);
> gimple_assign_set_rhs_from_tree (gsi, constr);
> update_stmt (gsi_stmt (*gsi));
> +
> + if (a_is_comparison && num_imm_uses (gimple_assign_lhs (assign)) == 0)
> + {
> + gimple_stmt_iterator gsi = gsi_for_stmt (assign);
> + gsi_remove (&gsi, true);
> + }
> }
>
> static tree
> --
> 2.27.0
>
