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)
+ 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);
+ 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;
>>> +}
>>>
