upstream

1 files changed, 7 insertions, 19 deletions

diff --git a/src/floatfns.c b/src/floatfns.c
index 305c78cae63..eaa1b32eb17 100644
--- a/src/floatfns.c
+++ b/src/floatfns.c
@@ -484,31 +484,19 @@ DEFUN ("expt", Fexpt, Sexpt, 2, 2, 0,
       && INTEGERP (arg2)   /* don't promote, if both are ints, and */
       && 0 <= XINT (arg2)) /* we are sure the result is not fractional */
     {                           /* this can be improved by pre-calculating */
-      EMACS_INT acc, x, y;      /* some binary powers of x then accumulating */
+      EMACS_INT y;              /* some binary powers of x then accumulating */
+      EMACS_UINT acc, x;  /* Unsigned so that overflow is well defined.  */
       Lisp_Object val;
 
       x = XINT (arg1);
       y = XINT (arg2);
-      acc = 1;
+      acc = (y & 1 ? x : 1);
 
-      if (y < 0)
+      while ((y >>= 1) != 0)
         {
-          if (x == 1)
-            acc = 1;
-          else if (x == -1)
-            acc = (y & 1) ? -1 : 1;
-          else
-            acc = 0;
-        }
-      else
-        {
-          while (y > 0)
-            {
-              if (y & 1)
-                acc *= x;
-              x *= x;
-              y >>= 1;
-            }
+          x *= x;
+          if (y & 1)
+            acc *= x;
         }
       XSETINT (val, acc);
       return val;