[PATCH] Fix PR61657 (undefined behavior in loop-iv.c)

[Markus Trippelsdorf]

bootstrap-ubsan shows:
 loop-iv.c:2626:14: runtime error: signed integer overflow: 9223372036854775806 
- -9223372036854775808 cannot be represented in type 'long int'

Fixed by moving the variables in question from signed to unsigned.

Bootstrapped and tested on ppc64le.
OK for trunk and gcc-5 branch?

Thanks.

2015-08-21  Markus Trippelsdorf  <mar...@trippelsdorf.de>

        PR rtl-optimization/61657
        * loop-iv.c (iv_number_of_iterations): Declare up and down as
        unsigned. Remove superflous uint64_t cast.

diff --git a/gcc/loop-iv.c b/gcc/loop-iv.c
index 6e9cc8c..1c9a159 100644
--- a/gcc/loop-iv.c
+++ b/gcc/loop-iv.c
@@ -2330,8 +2330,8 @@ iv_number_of_iterations (struct loop *loop, rtx_insn 
*insn, rtx condition,
   enum rtx_code cond;
   machine_mode mode, comp_mode;
   rtx mmin, mmax, mode_mmin, mode_mmax;
-  uint64_t s, size, d, inv, max;
-  int64_t up, down, inc, step_val;
+  uint64_t s, size, d, inv, max, up, down;
+  int64_t inc, step_val;
   int was_sharp = false;
   rtx old_niter;
   bool step_is_pow2;
@@ -2621,7 +2621,7 @@ iv_number_of_iterations (struct loop *loop, rtx_insn 
*insn, rtx condition,
          down = INTVAL (CONST_INT_P (iv0.base)
                         ? iv0.base
                         : mode_mmin);
-         max = (uint64_t) (up - down) / inc + 1;
+         max = (up - down) / inc + 1;
          if (!desc->infinite
              && !desc->assumptions)
            record_niter_bound (loop, max, false, true);
-- 
Markus