[tail-merge] Fix side-effect test in stmt_local_def

2018-06-21  Tom de Vries  <tdevries@suse.de>

	PR tree-optimization/85859
	* tree-ssa-tail-merge.c (stmt_local_def): Copy gimple_is_call
	test with comment from bb_no_side_effects_p.

	* gcc.dg/pr85859.c: New test.

From-SVN: r261844

gcc/ChangeLog

+2018-06-21  Tom de Vries  <tdevries@suse.de>
+
+	PR tree-optimization/85859
+	* tree-ssa-tail-merge.c (stmt_local_def): Copy gimple_is_call
+	test with comment from bb_no_side_effects_p.
+
 2018-06-21  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/86232

gcc/testsuite/ChangeLog

+2018-06-21  Tom de Vries  <tdevries@suse.de>
+
+	PR tree-optimization/85859
+	* gcc.dg/pr85859.c: New test.
+
 2018-06-21  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/86232

gcc/testsuite/gcc.dg/pr85859.c

+/* { dg-do run } */
+/* { dg-options "-ftree-tail-merge -Wno-div-by-zero -O2 -fno-dce -fno-isolate-erroneous-paths-dereference -fno-tree-dce -fno-tree-vrp" } */
+
+int b, c, d, e;
+
+__attribute__ ((noinline, noclone))
+int foo (short f)
+{
+  f %= 0;
+  return f;
+}
+
+int
+main (void)
+{
+  b = (unsigned char) __builtin_parity (d);
+  e ? foo (0) : (long) &c;
+  return 0;
+}

gcc/tree-ssa-tail-merge.c

@@ -301,7 +301,15 @@ stmt_local_def (gimple *stmt)
   if (gimple_vdef (stmt) != NULL_TREE
       || gimple_has_side_effects (stmt)
       || gimple_could_trap_p_1 (stmt, false, false)
-      || gimple_vuse (stmt) != NULL_TREE)
+      || gimple_vuse (stmt) != NULL_TREE
+      /* Copied from tree-ssa-ifcombine.c:bb_no_side_effects_p():
+	 const calls don't match any of the above, yet they could
+	 still have some side-effects - they could contain
+	 gimple_could_trap_p statements, like floating point
+	 exceptions or integer division by zero.  See PR70586.
+	 FIXME: perhaps gimple_has_side_effects or gimple_could_trap_p
+	 should handle this.  */
+      || is_gimple_call (stmt))
     return false;
 
   def_p = SINGLE_SSA_DEF_OPERAND (stmt, SSA_OP_DEF);