On Mon, Nov 16, 2020 at 10:26 AM Jiufu Guo <guoji...@linux.ibm.com> wrote:
>
> Jiufu Guo <guoji...@linux.ibm.com> writes:
>
> > Richard Biener <rguent...@suse.de> writes:
> >
> >> On Wed, 11 Nov 2020, Jiufu Guo wrote:
> >>
> >>>
> >>> Thanks a lot for the sugguestion from previous mails.
> >>> The patch was updated accordingly.
> >>>
> >>> This updated patch propagates loop-closed PHIs them out after
> >>> loop_optimizer_finalize under a new introduced flag. At some cases,
> >>> to clean up loop-closed PHIs would save efforts of optimization passes
> >>> after loopdone.
> >>>
> >>> This patch passes bootstrap and regtest on ppc64le. Is this ok for trunk?
> >>
> >> Comments below
> >>
> >>> free_numbers_of_iterations_estimates (fn);
> >>>
> >>> + if (flag_clean_up_loop_closed_phi
> >>
> >> Sorry if there was miscommunication but I've not meant to add a
> >> new user-visible flag but instead a flag argument to
> >> loop_optimizer_finalize
> >> (as said, you can default it to false to only need to change the
> >> one in fini_loops)
> > Sorry for misunderstand.
> > Updated the patch.
>
> Thanks for the comments! The patch was updated accordingly.
>
> This updated patch clean up loop closed PHIs in loop_optimizer_finalize,
> which is called when some loop optimizations are done. For some cases,
> this would save efforts of optimization passes after loopdone.
>
> gcc/ChangeLog:
> 2020-10-16 Jiufu Guo <guoji...@linux.ibm.com>
>
> * cfgloop.h (loop_optimizer_finalize): Add flag argument.
> * loop-init.c (loop_optimizer_finalize): Call
> clean_up_loop_closed_phi.
> * tree-cfgcleanup.h (clean_up_loop_closed_phi): New declare.
> * tree-ssa-loop.c (tree_ssa_loop_done): Call loop_optimizer_finalize
> with flag argument.
> * tree-ssa-propagate.c (clean_up_loop_closed_phi): New function.
>
> gcc/testsuite/ChangeLog:
> 2020-10-16 Jiufu Guo <guoji...@linux.ibm.com>
>
> * gcc.dg/tree-ssa/loopclosedphi.c: New test.
>
> ---
> gcc/cfgloop.h | 2 +-
> gcc/loop-init.c | 9 ++-
> gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c | 21 +++++++
> gcc/tree-cfgcleanup.h | 1 +
> gcc/tree-ssa-loop.c | 2 +-
> gcc/tree-ssa-propagate.c | 63 +++++++++++++++++++
> 6 files changed, 95 insertions(+), 3 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c
>
> diff --git a/gcc/cfgloop.h b/gcc/cfgloop.h
> index d14689dc31f..438b1f779bb 100644
> --- a/gcc/cfgloop.h
> +++ b/gcc/cfgloop.h
> @@ -824,7 +824,7 @@ extern void init_set_costs (void);
>
> /* Loop optimizer initialization. */
> extern void loop_optimizer_init (unsigned);
> -extern void loop_optimizer_finalize (function *);
> +extern void loop_optimizer_finalize (function *, bool = false);
> inline void
> loop_optimizer_finalize ()
> {
> diff --git a/gcc/loop-init.c b/gcc/loop-init.c
> index 401e5282907..0cb6f509b89 100644
> --- a/gcc/loop-init.c
> +++ b/gcc/loop-init.c
> @@ -33,6 +33,7 @@ along with GCC; see the file COPYING3. If not see
> #include "tree-ssa-loop-niter.h"
> #include "loop-unroll.h"
> #include "tree-scalar-evolution.h"
> +#include "tree-cfgcleanup.h"
>
>
> /* Apply FLAGS to the loop state. */
> @@ -133,7 +134,7 @@ loop_optimizer_init (unsigned flags)
> /* Finalize loop structures. */
>
> void
> -loop_optimizer_finalize (struct function *fn)
> +loop_optimizer_finalize (struct function *fn, bool clean_loop_closed_phi)
> {
> class loop *loop;
> basic_block bb;
> @@ -145,6 +146,12 @@ loop_optimizer_finalize (struct function *fn)
>
> free_numbers_of_iterations_estimates (fn);
>
> + if (clean_loop_closed_phi && loops_state_satisfies_p (fn, LOOP_CLOSED_SSA))
> + {
> + clean_up_loop_closed_phi (fn);
> + loops_state_clear (fn, LOOP_CLOSED_SSA);
> + }
> +
> /* If we should preserve loop structure, do not free it but clear
> flags that advanced properties are there as we are not preserving
> that in full. */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c
> b/gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c
> new file mode 100644
> index 00000000000..d71b757fbca
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/loopclosedphi.c
> @@ -0,0 +1,21 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -fno-tree-ch -w -fdump-tree-loopdone-details" } */
> +
> +void
> +t6 (int qz, int wh)
> +{
> + int jl = wh;
> +
> + while (1.0 * qz / wh < 1)
> + {
> + qz = wh * (wh + 2);
> +
> + while (wh < 1)
> + jl = 0;
> + }
> +
> + while (qz < 1)
> + qz = jl * wh;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "Replacing" 2 "loopdone"} } */
> diff --git a/gcc/tree-cfgcleanup.h b/gcc/tree-cfgcleanup.h
> index 6ff6726bfe4..9e368d63709 100644
> --- a/gcc/tree-cfgcleanup.h
> +++ b/gcc/tree-cfgcleanup.h
> @@ -26,5 +26,6 @@ extern bool cleanup_tree_cfg (unsigned = 0);
> extern bool fixup_noreturn_call (gimple *stmt);
> extern bool delete_unreachable_blocks_update_callgraph (cgraph_node
> *dst_node,
> bool update_clones);
> +extern unsigned clean_up_loop_closed_phi (function *);
>
> #endif /* GCC_TREE_CFGCLEANUP_H */
> diff --git a/gcc/tree-ssa-loop.c b/gcc/tree-ssa-loop.c
> index 5e8365d4e83..339a0c50bc8 100644
> --- a/gcc/tree-ssa-loop.c
> +++ b/gcc/tree-ssa-loop.c
> @@ -529,7 +529,7 @@ tree_ssa_loop_done (void)
> {
> free_numbers_of_iterations_estimates (cfun);
> scev_finalize ();
> - loop_optimizer_finalize ();
> + loop_optimizer_finalize (cfun, true);
> return 0;
> }
>
> diff --git a/gcc/tree-ssa-propagate.c b/gcc/tree-ssa-propagate.c
> index 87dbf55fab9..daa1db82afc 100644
> --- a/gcc/tree-ssa-propagate.c
> +++ b/gcc/tree-ssa-propagate.c
> @@ -1549,3 +1549,66 @@ propagate_tree_value_into_stmt (gimple_stmt_iterator
> *gsi, tree val)
> else
> gcc_unreachable ();
> }
> +
> +/* Check exits of each loop in FUN, walk over loop closed PHIs in
> + each exit basic block and propagate degenerate PHIs. */
> +
> +unsigned
> +clean_up_loop_closed_phi (function *fun)
> +{
> + unsigned i;
> + edge e;
> + gphi *phi;
> + tree rhs;
> + tree lhs;
> + gphi_iterator gsi;
> + struct loop *loop;
> +
> + /* Check dominator info before get loop-close PHIs from loop exits. */
> + if (dom_info_state (CDI_DOMINATORS) != DOM_OK)
Please change this to
/* Avoid possibly quadratic work when scanning for loop exits across
all loops of a nest. */
if (!loop_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
return 0;
> + return 0;
> +
> + /* Walk over loop in function. */
> + FOR_EACH_LOOP_FN (fun, loop, 0)
> + {
> + /* Check each exit edege of loop. */
> + auto_vec<edge> exits = get_loop_exit_edges (loop);
> + FOR_EACH_VEC_ELT (exits, i, e)
> + if (single_pred_p (e->dest))
> + /* Walk over loop-closed PHIs. */
> + for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi);)
> + {
> + phi = gsi.phi ();
> + rhs = degenerate_phi_result (phi);
rhs = gimple_phi_arg_def (phi, 0);
OK with that changes.
Thanks,
Richard.
> + lhs = gimple_phi_result (phi);
> +
> + if (rhs && may_propagate_copy (lhs, rhs))
> + {
> + /* Dump details. */
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + {
> + fprintf (dump_file, " Replacing '");
> + print_generic_expr (dump_file, lhs, dump_flags);
> + fprintf (dump_file, "' with '");
> + print_generic_expr (dump_file, rhs, dump_flags);
> + fprintf (dump_file, "'\n");
> + }
> +
> + use_operand_p use_p;
> + imm_use_iterator iter;
> + gimple *use_stmt;
> + FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs)
> + {
> + FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
> + replace_exp (use_p, rhs);
> + update_stmt (use_stmt);
> + }
> + remove_phi_node (&gsi, true);
> + }
> + else
> + gsi_next (&gsi);
> + }
> + }
> +
> + return 0;
> +}
> --
> 2.25.1
>
>
>
>
> >>
> >>> + && loops_state_satisfies_p (fn, LOOP_CLOSED_SSA))
> >>> + {
> >>> + clean_up_loop_closed_phi (fn);
> >>> + loops_state_clear (fn, LOOP_CLOSED_SSA);
> >>> + }
> >>> +
> > ......
> >>> + gphi *phi;
> >>> + tree rhs;
> >>> + tree lhs;
> >>> + gphi_iterator gsi;
> >>> + struct loop *loop;
> >>> + bool cfg_altered = false;
> >>> +
> >>> + /* Check dominator info before get loop-close PHIs from loop exits. */
> >>> + if (dom_info_state (CDI_DOMINATORS) != DOM_OK)
> >>
> >> Why?
> >>
> > As you said, loop_optimizer_finalize is also called from where dominator
> > info is not ready, e.g. called from: vrp(execute_vrp).
> > At there, loop exits info is not ready, and then
> > get_loop_exit_edges/get_loop_body_with_size function does not work.
> >
> >>> + /* Walk over loop in function. */
> >>> + FOR_EACH_LOOP_FN (fun, loop, 0)
> >>> + {
> >>> + /* Check each exit edege of loop. */
> >>> + auto_vec<edge> exits = get_loop_exit_edges (loop);
> >>> + FOR_EACH_VEC_ELT (exits, i, e)
> >>> + if (single_pred_p (e->dest))
> >>> + /* Walk over loop-closed PHIs. */
> >>> + for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi);)
> >>> + {
> >>> + phi = gsi.phi ();
> >>> + rhs = degenerate_phi_result (phi);
> >>
> >> You have a single predecessor, thus the result is always degenerate.
> >>
> >>> + lhs = gimple_phi_result (phi);
> >>> +
> >>> + if (rhs && may_propagate_copy (lhs, rhs))
> >>> + {
> >>> + gimple_stmt_iterator psi = gsi;
> >>> + /* Advance the iterator before stmt is removed. */
> >>> + gsi_next (&gsi);
> >>
> >> remove_phi_node should take care of this, you shouldn't need this
> >> (just do not advance the iterator when you remove the PHI node).
> >>
> > Yeap, get it! Thanks, will update the patch accordingly.
> >>> +
> > ......
> >>> +
> >>> + replace_uses_by (lhs, rhs);
> >>> + remove_phi_node (&psi, true);
> >>> + cfg_altered = true;
> >>
> >> in the end the return value is unused but I think we should avoid
> >> altering the CFG since doing so requires it to be cleaned up for
> >> unreachable blocks. That means to open-code replace_uses_by as
> >>
> >> imm_use_iterator imm_iter;
> >> use_operand_p use;
> >> gimple *stmt;
> >> FOR_EACH_IMM_USE_STMT (stmt, imm_iter, name)
> >> {
> >> FOR_EACH_IMM_USE_ON_STMT (use, imm_iter)
> >> replace_exp (use, val);
> >> update_stmt (stmt);
> >> }
> >
> > Thansk! This could also save some code in replace_uses_by.
> >
> > BR.
> > Jiufu Guo
> >>
> >> Thanks,
> >> Richard.
> >>
> >>> + }
> >>> + else
> >>> + gsi_next (&gsi);
> >>> + }
> >>> + }
> >>> +
> >>> + return cfg_altered;
> >>> +}
> >>>
