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tree-optimization/107153 - autopar SSA update issue

Message ID 20221007122659.274CA13A3D@imap2.suse-dmz.suse.de
State New, archived
Headers
Series tree-optimization/107153 - autopar SSA update issue |

Commit Message

Richard Biener Oct. 7, 2022, 12:26 p.m. UTC 
  autopar performs insertion of stores, eventually requiring a
virtual loop PHI and assorted LC PHI adjustments which we intend
to do once after the pass finishes.  But we also perform intermediate
update_ssa after loop duplication which can lose this fact.  The
following forces renaming of the virtual operand before the final
SSA update to fix that.  It also removes the explicit update_ssa
call from the gimple_duplicate_sese_tail utility as has been done
for all other such utilities and instead performs the SSA update
from autopar.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

	PR tree-optimization/107153
	* tree-cfg.cc (gimple_duplicate_sese_tail): Do not update
	SSA form here.
	* tree-parloops.cc (gen_parallel_loop): Update SSA form
	after to-exit-first transform, no PHI insertion is necessary.
	(pass_parallelize_loops::execute): Force re-write of the
	virtual operand SSA web.

	* gcc.dg/autopar/pr107153.c: New testcase.
---
 gcc/testsuite/gcc.dg/autopar/pr107153.c | 17 +++++++++++++++++
 gcc/tree-cfg.cc                         |  2 --
 gcc/tree-parloops.cc                    |  5 +++++
 3 files changed, 22 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/autopar/pr107153.c
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Patch

diff --git a/gcc/testsuite/gcc.dg/autopar/pr107153.c b/gcc/testsuite/gcc.dg/autopar/pr107153.c
new file mode 100644
index 00000000000..2391a674d63
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/autopar/pr107153.c
@@ -0,0 +1,17 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O1 -floop-parallelize-all -ftree-parallelize-loops=2 -fno-tree-dominator-opts" } */
+
+void
+foo (int x, int y)
+{
+  int i;
+
+  for (i = 0; i < 2; i++)
+    {
+    }
+
+  while (x)
+    if (!y)
+      while (y)
+        ++y;
+}
diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index 09fa7b64584..42f40f17c56 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -6926,8 +6926,6 @@  gimple_duplicate_sese_tail (edge entry, edge exit,
   /* Anything that is outside of the region, but was dominated by something
      inside needs to update dominance info.  */
   iterate_fix_dominators (CDI_DOMINATORS, doms, false);
-  /* Update the SSA web.  */
-  update_ssa (TODO_update_ssa);
 
   if (free_region_copy)
     free (region_copy);
diff --git a/gcc/tree-parloops.cc b/gcc/tree-parloops.cc
index e4a148b5365..e680d97dd04 100644
--- a/gcc/tree-parloops.cc
+++ b/gcc/tree-parloops.cc
@@ -3131,6 +3131,7 @@  gen_parallel_loop (class loop *loop,
 	 to the exit of the loop.  */
       transform_to_exit_first_loop (loop, reduction_list, nit);
     }
+  update_ssa (TODO_update_ssa_no_phi);
 
   /* Generate initializations for reductions.  */
   if (!reduction_list->is_empty ())
@@ -4215,6 +4216,10 @@  pass_parallelize_loops::execute (function *fun)
 
       checking_verify_loop_structure ();
 
+      /* ???  Intermediate SSA updates with no PHIs might have lost
+	 the virtual operand renaming needed by separate_decls_in_region,
+	 make sure to rename them again.  */
+      mark_virtual_operands_for_renaming (fun);
       update_ssa (TODO_update_ssa);
       if (in_loop_pipeline)
 	rewrite_into_loop_closed_ssa (NULL, 0);