re PR rtl-optimization/78241 (wrong code with -funroll-loops)

	PR rtl-optimization/78241
	* loop-unroll.c (unroll_loop_runtime_iterations): Don't adjust 'niter', but
	emit initial peel copy if niter expr is not reliable.

	* gcc.dg/pr78241.c: New test.

From-SVN: r242047

gcc/ChangeLog

+2016-11-10  Pat Haugen  <pthaugen@us.ibm.com>
+
+	PR rtl-optimization/78241
+	* loop-unroll.c (unroll_loop_runtime_iterations): Don't adjust 'niter', but
+	emit initial peel copy if niter expr is not reliable.
+
 2016-11-10  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* dwarf2cfi.c (dump_cfi_row): Add forward declaration.

gcc/loop-unroll.c

@@ -918,9 +918,10 @@ unroll_loop_runtime_iterations (struct loop *loop)
   if (tmp != niter)
     emit_move_insn (niter, tmp);
 
-  /* For loops that exit at end, add one to niter to account for first pass
-     through loop body before reaching exit test. */
-  if (exit_at_end)
+  /* For loops that exit at end and whose number of iterations is reliable,
+     add one to niter to account for first pass through loop body before
+     reaching exit test. */
+  if (exit_at_end && !desc->noloop_assumptions)
     {
       niter = expand_simple_binop (desc->mode, PLUS,
 				   niter, const1_rtx,
@@ -946,7 +947,7 @@ unroll_loop_runtime_iterations (struct loop *loop)
 
   auto_sbitmap wont_exit (max_unroll + 2);
 
-  if (extra_zero_check)
+  if (extra_zero_check || desc->noloop_assumptions)
     {
       /* Peel the first copy of loop body.  Leave the exit test if the number
 	 of iterations is not reliable.  Also record the place of the extra zero

gcc/testsuite/ChangeLog

+2016-11-10  Pat Haugen  <pthaugen@us.ibm.com>
+
+	PR rtl-optimization/78241
+	* gcc.dg/pr78241.c: New test.
+
 2016-11-10  Jakub Jelinek  <jakub@redhat.com>
 
 	* gfortran.dg/openmp-define-3.f90: Expect 201511 instead of

gcc/testsuite/gcc.dg/pr78241.c

+/* { dg-do run } */
+/* { dg-options "-Og -funroll-loops" } */
+
+static __attribute__((noinline, noclone)) unsigned
+foo (unsigned x)
+{
+  do
+    x++;
+  while (x <= 15);
+  return x;
+}
+
+int main ()
+{
+  unsigned x = foo (-2);
+  if (x != (unsigned)-1)
+    __builtin_abort();
+  return 0;
+}
+