re PR tree-optimization/79622 (Wrong code w/ -O2 -floop-nest-optimize)

2017-09-18  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/79622
	* graphite-scop-detection.c (build_cross_bb_scalars_def): Properly
	handle PHIs.
	(build_cross_bb_scalars_use): Likewise.

	* gcc.dg/graphite/pr79622.c: New testcase.

From-SVN: r252905

gcc/ChangeLog

+2017-09-18  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/79622
+	* graphite-scop-detection.c (build_cross_bb_scalars_def): Properly
+	handle PHIs.
+	(build_cross_bb_scalars_use): Likewise.
+
 2017-09-18  Pierre-Marie de Rodat  <derodat@adacore.com>
 
 	* cgraph.h (cgraph_thunk_info): Fix a typo in a comment.

gcc/graphite-scop-detection.c

@@ -1744,7 +1744,9 @@ build_cross_bb_scalars_def (scop_p scop, tree def, basic_block def_bb,
   gimple *use_stmt;
   imm_use_iterator imm_iter;
   FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, def)
-    if (def_bb != gimple_bb (use_stmt) && !is_gimple_debug (use_stmt))
+    if ((def_bb != gimple_bb (use_stmt) && !is_gimple_debug (use_stmt))
+	/* PHIs have their effect at "BBs" on the edges.  See PR79622.  */
+	|| gimple_code (SSA_NAME_DEF_STMT (def)) == GIMPLE_PHI)
       {
 	writes->safe_push (def);
 	DEBUG_PRINT (dp << "Adding scalar write: ";
@@ -1758,7 +1760,8 @@ build_cross_bb_scalars_def (scop_p scop, tree def, basic_block def_bb,
       }
 }
 
-/* Record DEF if it is used in other bbs different than DEF_BB in the SCOP.  */
+/* Record USE if it is defined in other bbs different than USE_STMT
+   in the SCOP.  */
 
 static void
 build_cross_bb_scalars_use (scop_p scop, tree use, gimple *use_stmt,
@@ -1774,7 +1777,9 @@ build_cross_bb_scalars_use (scop_p scop, tree use, gimple *use_stmt,
     return;
 
   gimple *def_stmt = SSA_NAME_DEF_STMT (use);
-  if (gimple_bb (def_stmt) != gimple_bb (use_stmt))
+  if (gimple_bb (def_stmt) != gimple_bb (use_stmt)
+      /* PHIs have their effect at "BBs" on the edges.  See PR79622.  */
+      || gimple_code (def_stmt) == GIMPLE_PHI)
     {
       DEBUG_PRINT (dp << "Adding scalar read: ";
 		   print_generic_expr (dump_file, use);

gcc/testsuite/ChangeLog

+2017-09-18  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/79622
+	* gcc.dg/graphite/pr79622.c: New testcase.
+
 2017-09-17  Daniel Santos  <daniel.santos@pobox.com>
 
 	gcc.target/i386/pr82196-1.c: New test.

gcc/testsuite/gcc.dg/graphite/pr79622.c

+/* { dg-do run } */
+/* { dg-options "-O2 -floop-nest-optimize" } */
+
+int bf;
+
+int
+main (void)
+{
+  int dc[5];
+
+  for (bf = 0; bf < 2; ++bf)
+    {
+      int l9, g5 = -1;
+
+      for (l9 = 0; l9 < 5; ++l9)
+	{
+	  dc[l9] = g5;
+	  g5 = (dc[l9] > 0);
+	}
+    }
+
+  if (dc[0] != -1)
+    __builtin_abort ();
+
+  return 0;
+}