Simplify fixnum division slightly

* src/data.c (arith_driver): Streamline fixnum division a bit
more, and add a comment about why overflow is impossible.
This responds to a private comment by Stefan Monnier.

1 files changed, 6 insertions, 4 deletions

diff --git a/src/data.c b/src/data.c
index 955e5073900..649dc174f90 100644
--- a/src/data.c
+++ b/src/data.c
@@ -2943,7 +2943,7 @@ arith_driver (enum arithop code, ptrdiff_t nargs, Lisp_Object *args,
 
         /* Set ACCUM to the next operation's result if it fits,
            else exit the loop.  */
-        bool overflow = false;
+        bool overflow;
         intmax_t a;
         switch (code)
           {
@@ -2953,9 +2953,11 @@ arith_driver (enum arithop code, ptrdiff_t nargs, Lisp_Object *args,
           case Adiv:
             if (next == 0)
               xsignal0 (Qarith_error);
-            eassert (! INT_DIVIDE_OVERFLOW (accum, next));
-            a = accum / next;
-            break;
+            /* This cannot overflow, as integer overflow can
+               occur only if the dividend is INTMAX_MIN, but
+               INTMAX_MIN < MOST_NEGATIVE_FIXNUM <= accum.  */
+            accum /= next;
+            continue;
           case Alogand: accum &= next; continue;
           case Alogior: accum |= next; continue;
           case Alogxor: accum ^= next; continue;