From b2879f8f361c611221d2f7be603fb80a260b3010 Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Thu, 9 Jun 2022 18:44:14 -0700
Subject: [PATCH] Stage bignum_simplify

---
 runtime.c | 40 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/runtime.c b/runtime.c
index 86bbaa4c..6aee21b5 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2446,6 +2446,43 @@ int bignum2_num_digits(bignum2_type *bn, int radix)
   return len;
 }
 
+/* Simplification: scan trailing zeroes, then return a fixnum if the
+ * value fits, or trim the bignum's length.  If the bignum was stored
+ * in scratch space, we mark it as reclaimable.  This means any
+ * references to the original bignum are invalid after simplification!
+ */
+//C_regparm C_word C_fcall C_bignum_simplify(C_word big)
+//{
+//  C_uword *start = C_bignum_digits(big),
+//          *last_digit = start + C_bignum_size(big) - 1,
+//          *scan = last_digit, tmp;
+//  int length;
+//
+//  while (scan >= start && *scan == 0)
+//    scan--;
+//  length = scan - start + 1;
+//
+//  switch(length) {
+//  case 0:
+//    if (C_in_scratchspacep(C_internal_bignum_vector(big)))
+//      C_mutate_scratch_slot(NULL, C_internal_bignum_vector(big));
+//    return C_fix(0);
+//  case 1:
+//    tmp = *start;
+//    if (C_bignum_negativep(big) ?
+//        !(tmp & C_INT_SIGN_BIT) && C_fitsinfixnump(-(C_word)tmp) :
+//        C_ufitsinfixnump(tmp)) {
+//      if (C_in_scratchspacep(C_internal_bignum_vector(big)))
+//        C_mutate_scratch_slot(NULL, C_internal_bignum_vector(big));
+//      return C_bignum_negativep(big) ? C_fix(-(C_word)tmp) : C_fix(tmp);
+//    }
+//    /* FALLTHROUGH */
+//  default:
+//    if (scan < last_digit) C_bignum_mutate_size(big, length);
+//    return big;
+//  }
+//}
+
 static uint32_t bignum_digits_destructive_scale_down(uint32_t *start, uint32_t *end, uint32_t denominator)
 {
   uint32_t digit, k = 0;
@@ -2724,7 +2761,8 @@ object bignum2_plus_unsigned(void *data, bignum2_type *x, bignum2_type *y, int n
   }
   assert(scan_r <= end_r);
 
-  return C_bignum_simplify(result);
+  // TODO: return C_bignum_simplify(result);
+  return NULL; // DEBUG only!
 }
 
 object Cyc_symbol2string(void *data, object cont, object sym)