tree-optimization/104528 - free niter estimates after DSE

When DSE removes a trivially dead def we have to reset niter information
on loops since that might refer to it.  The patch also adds verification
to make sure this does not happen.

2022-02-14  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/104528
	* tree-ssa.h (find_released_ssa_name): Declare.
	* tree-ssa.cc (find_released_ssa_name): Export.
	* cfgloop.cc (verify_loop_structure): Look for released
	SSA names in loops nb_iterations.
	* tree-ssa-dse.cc (pass_dse::execute): Release number of iteration
	estimates.

	* gfortran.dg/pr104528.f: New testcase.

gcc/cfgloop.cc

@@ -31,6 +31,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "cfgloop.h"
 #include "gimple-iterator.h"
 #include "dumpfile.h"
+#include "tree-ssa.h"
+#include "tree-pretty-print.h"
 
 static void flow_loops_cfg_dump (FILE *);
 
@@ -1561,6 +1563,17 @@ verify_loop_structure (void)
 		err = 1;
 	      }
 	}
+
+      /* Check cached number of iterations for released SSA names.  */
+      tree ref;
+      if (loop->nb_iterations
+	  && (ref = walk_tree (&loop->nb_iterations,
+			       find_released_ssa_name, NULL, NULL)))
+	{
+	  error ("loop %d%'s number of iterations %qE references the"
+		 " released SSA name %qE", i, loop->nb_iterations, ref);
+	  err = 1;
+	}
     }
 
   /* Check irreducible loops.  */

gcc/testsuite/gfortran.dg/pr104528.f

@@ -0,0 +1,44 @@
+! { dg-do compile }
+! { dg-options "-O2 -fpeel-loops -ftree-loop-vectorize -fno-tree-scev-cprop --param iv-max-considered-uses=2" }
+      REAL               FUNCTION FOO(M, N, A, W)
+
+      INTEGER            M, N
+
+      REAL               W(*)
+      COMPLEX            A(*)
+
+      INTEGER            II, JI, JJ, KK, LL, MP
+
+      EXTERNAL           BAR
+
+      INTEGER            QUX
+      EXTERNAL           QUX
+
+      CALL BAR(II)
+
+      IF (M .EQ. 0) THEN
+         IF (N .EQ. 0) THEN
+            DO 140 KK = II, II + MP
+               W(KK) = 0
+ 140        CONTINUE
+         ELSE
+            KK = II + MP
+         END IF
+
+         DO 130 JI = KK, KK + MP
+            DO 120 LL = JJ, JJ + MP
+               DO 110 KK = II, II + MP
+                  W(KK) = (A(KK))
+ 110           CONTINUE
+ 120        CONTINUE
+ 130     CONTINUE
+
+         IF (W(KK) .EQ. 0) THEN
+            FOO = W(QUX(MP, W, 1))
+         END IF
+
+      END IF
+
+      RETURN
+
+      END

gcc/tree-ssa-dse.cc

@@ -44,6 +44,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "ipa-modref-tree.h"
 #include "ipa-modref.h"
 #include "target.h"
+#include "tree-ssa-loop-niter.h"
 
 /* This file implements dead store elimination.
 
@@ -1418,6 +1419,8 @@ unsigned int
 pass_dse::execute (function *fun)
 {
   unsigned todo = 0;
+  bool released_def = false;
+
   need_eh_cleanup = BITMAP_ALLOC (NULL);
   need_ab_cleanup = BITMAP_ALLOC (NULL);
   auto_sbitmap live_bytes (param_dse_max_object_size);
@@ -1460,6 +1463,7 @@ pass_dse::execute (function *fun)
 		  if (gsi_remove (&gsi, true) && need_eh_cleanup)
 		    bitmap_set_bit (need_eh_cleanup, bb->index);
 		  release_defs (stmt);
+		  released_def = true;
 		}
 	    }
 	  if (gsi_end_p (gsi))
@@ -1481,6 +1485,7 @@ pass_dse::execute (function *fun)
 		}
 	      remove_phi_node (&si, true);
 	      removed_phi = true;
+	      released_def = true;
 	    }
 	  else
 	    gsi_next (&si);
@@ -1506,6 +1511,9 @@ pass_dse::execute (function *fun)
   BITMAP_FREE (need_eh_cleanup);
   BITMAP_FREE (need_ab_cleanup);
 
+  if (released_def)
+    free_numbers_of_iterations_estimates (fun);
+
   return todo;
 }
 

gcc/tree-ssa.cc

@@ -272,7 +272,7 @@ target_for_debug_bind (tree var)
 /* Called via walk_tree, look for SSA_NAMEs that have already been
    released.  */
 
-static tree
+tree
 find_released_ssa_name (tree *tp, int *walk_subtrees, void *data_)
 {
   struct walk_stmt_info *wi = (struct walk_stmt_info *) data_;

gcc/tree-ssa.h

@@ -49,6 +49,7 @@ extern void init_tree_ssa (function *, int size = 0);
 extern void delete_tree_ssa (function *);
 extern bool tree_ssa_useless_type_conversion (tree);
 extern tree tree_ssa_strip_useless_type_conversions (tree);
+extern tree find_released_ssa_name (tree *, int *, void *);
 
 
 extern bool ssa_defined_default_def_p (tree t);