[gcc r13-1467] tree-optimization/106182 - LC SSA after CFG cleanup

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:b55284f4a1235fccd8254f539ddc6b869580462b

commit r13-1467-gb55284f4a1235fccd8254f539ddc6b869580462b
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Jul 4 15:03:33 2022 +0200

    tree-optimization/106182 - LC SSA after CFG cleanup
    
    The testcase shows that when cleaning up the CFG we can end up
    with broken LC SSA (for virtual operands with the testcase).  The
    case here involves deleting a loop after which it is not enough
    to scan the blocks with changed loop depth for SSA uses that need
    to be rewritten.  So make fix_loop_sturcture return the sum of
    the number of new loops and the number of deleted loops.
    
            PR tree-optimization/106182
            * loop-init.cc (fix_loop_structure): Return the number
            of newly discovered plus the number of deleted loops.
            * tree-cfgcleanup.cc (repair_loop_structures): Adjust
            variable name.
    
            * gcc.dg/torture/pr106182.c: New testcase.

Diff:
---
 gcc/loop-init.cc                        | 10 +++++-----
 gcc/testsuite/gcc.dg/torture/pr106182.c | 18 ++++++++++++++++++
 gcc/tree-cfgcleanup.cc                  |  6 +++---
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/gcc/loop-init.cc b/gcc/loop-init.cc
index 648aa290916..b9e07973dd6 100644
--- a/gcc/loop-init.cc
+++ b/gcc/loop-init.cc
@@ -194,7 +194,7 @@ loop_fini_done:
    If CHANGED_BBS is not NULL, basic blocks whose loop depth has changed are
    marked in it.
 
-   Returns the number of new discovered loops.  */
+   Returns the number of new discovered plus the number of removed loops.  */
 
 unsigned
 fix_loop_structure (bitmap changed_bbs)
@@ -277,7 +277,7 @@ fix_loop_structure (bitmap changed_bbs)
     }
 
   /* Finally free deleted loops.  */
-  bool any_deleted = false;
+  unsigned n_deleted = 0;
   class loop *loop;
   FOR_EACH_VEC_ELT (*get_loops (cfun), i, loop)
     if (loop && loop->header == NULL)
@@ -311,12 +311,12 @@ fix_loop_structure (bitmap changed_bbs)
 	  }
 	(*get_loops (cfun))[i] = NULL;
 	flow_loop_free (loop);
-	any_deleted = true;
+	n_deleted++;
       }
 
   /* If we deleted loops then the cached scalar evolutions refering to
      those loops become invalid.  */
-  if (any_deleted && scev_initialized_p ())
+  if (n_deleted > 0 && scev_initialized_p ())
     scev_reset_htab ();
 
   loops_state_clear (LOOPS_NEED_FIXUP);
@@ -328,7 +328,7 @@ fix_loop_structure (bitmap changed_bbs)
 
   timevar_pop (TV_LOOP_INIT);
 
-  return number_of_loops (cfun) - old_nloops;
+  return number_of_loops (cfun) - old_nloops + n_deleted;
 }
 \f
 /* The RTL loop superpass.  The actual passes are subpasses.  See passes.cc for
diff --git a/gcc/testsuite/gcc.dg/torture/pr106182.c b/gcc/testsuite/gcc.dg/torture/pr106182.c
new file mode 100644
index 00000000000..6b5c2493fd6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr106182.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-funswitch-loops" } */
+
+short var_32;
+int test_var_0;
+unsigned char test_var_6;
+char test_var_13;
+void test(int var_2)
+{
+  for (;;)
+    for (short i_7; i_7 < test_var_13; i_7 += 1)
+      for (; test_var_0;) {
+        for (; var_2;)
+          var_32 = 0;
+        for (char i_19; i_19 < test_var_6 + 135; i_19 += 200)
+          ;
+      }
+}
diff --git a/gcc/tree-cfgcleanup.cc b/gcc/tree-cfgcleanup.cc
index a6d0bf2c40a..3b24e021b6b 100644
--- a/gcc/tree-cfgcleanup.cc
+++ b/gcc/tree-cfgcleanup.cc
@@ -1170,13 +1170,13 @@ static void
 repair_loop_structures (void)
 {
   bitmap changed_bbs;
-  unsigned n_new_loops;
+  unsigned n_new_or_deleted_loops;
 
   calculate_dominance_info (CDI_DOMINATORS);
 
   timevar_push (TV_REPAIR_LOOPS);
   changed_bbs = BITMAP_ALLOC (NULL);
-  n_new_loops = fix_loop_structure (changed_bbs);
+  n_new_or_deleted_loops = fix_loop_structure (changed_bbs);
 
   /* This usually does nothing.  But sometimes parts of cfg that originally
      were inside a loop get out of it due to edge removal (since they
@@ -1184,7 +1184,7 @@ repair_loop_structures (void)
      irreducible loop can become reducible - in this case force a full
      rewrite into loop-closed SSA form.  */
   if (loops_state_satisfies_p (LOOP_CLOSED_SSA))
-    rewrite_into_loop_closed_ssa (n_new_loops ? NULL : changed_bbs,
+    rewrite_into_loop_closed_ssa (n_new_or_deleted_loops ? NULL : changed_bbs,
 				  TODO_update_ssa);
 
   BITMAP_FREE (changed_bbs);