Rewrite without gotos

1 files changed, 11 insertions, 135 deletions

diff --git a/src/mp_monty.cpp b/src/mp_monty.cpp
index bafa679c9..5edee3e2d 100644
--- a/src/mp_monty.cpp
+++ b/src/mp_monty.cpp
@@ -8,9 +8,6 @@
 #include <botan/mp_asm.h>
 #include <botan/mp_asmi.h>
 
-#include <assert.h>
-#include <stdio.h>
-
 namespace Botan {
 
 extern "C" {
@@ -48,140 +45,24 @@ void bigint_monty_redc(word z[], u32bit z_size,
          }
       }
 
-#if 0
-   if(bigint_cmp(z + x_size, x_size + 1, x, x_size) >= 0)
-      bigint_sub2(z + x_size, x_size + 1, x, x_size);
-#else
-   /*
-
-s32bit bigint_cmp(const word x[], u32bit x_size,
-                  const word y[], u32bit y_size)
-   {
-   if(x_size < y_size) { return (-bigint_cmp(y, y_size, x, x_size)); }
-
-   while(x_size > y_size)
-      {
-      if(x[x_size-1])
-         return 1;
-      x_size--;
-      }
-   for(u32bit j = x_size; j > 0; --j)
-      {
-      if(x[j-1] > y[j-1]) return 1;
-      if(x[j-1] < y[j-1]) return -1;
-      }
-   return 0;
-   }
-
-   */
-
-   /*
-
-   if((x_size+1) < x_size) { return (-bigint_cmp(y, x_size, x, (x_size+1))); }
-
-   while((x_size+1) > x_size)
-      {
-      if(x[(x_size+1)-1])
-         return 1;
-      (x_size+1)--;
-      }
-   for(u32bit j = (x_size+1); j > 0; --j)
-      {
-      if(x[j-1] > y[j-1]) return 1;
-      if(x[j-1] < y[j-1]) return -1;
-      }
-   return 0;
-
-   ->
-
-   //can't happen: if((x_size+1) < x_size) { return (-bigint_cmp(y, x_size, x, (x_size+1))); }
-
-   // always true: while((x_size+1) > x_size)
-   // {
-      if(x[x_size])
-          return do_sub();
-      //rewrite as x_size: (x_size+1)--;
-      }
-   for(u32bit j = x_size; j > 0; --j)
-      {
-      if(x[j-1] > y[j-1])
-          return do_sub();
-      if(x[j-1] < y[j-1])
-          return;
-      }
-   return do_sub();
-
-   ->
-
-   cleanup:
-
-   if(x[x_size])
-      return do_sub();
-
-   for(u32bit j = x_size; j > 0; --j)
-      {
-      if(x[j-1] > y[j-1])
-          return do_sub();
-      if(x[j-1] < y[j-1])
-          return;
-      }
-   return do_sub();
-
-   -> arg rewrite
-
-   bigint_cmp(z + x_size, x_size + 1, x, x_size)
-
-   x = z + x_size
-   x_size = x_size + 1
-   y = x
-   y_size = x_size
-   ^ !!!
-
-   if(z[x_size + x_size + 1])
-      return do_sub();
-
-   for(u32bit j = x_size; j > 0; --j)
-      {
-      if(z[x_size+j-1] > x[j-1])
-          return do_sub();
-      if(z[x_size+j-1] < x[j-1])
-          return;
-      }
-   return do_sub();
-
+   /* Check if z[x_size...x_size+1] >= x[0...x_size]
+      This is bigint_cmp, inlined
    */
-
-   word carry = 0;
-   const u32bit blocks = x_size - (x_size % 8);
-
-   if(z[x_size + x_size])
-      {
-      //assert((bigint_cmp(z + x_size, x_size + 1, x, x_size) > 0);
-      goto do_sub;
-      }
-
-   for(u32bit j = x_size; j > 0; --j)
+   if(!z[x_size + x_size])
       {
-      if(z[x_size + j - 1] > x[j-1])
+      for(u32bit j = x_size; j > 0; --j)
          {
-         //assert((bigint_cmp(z + x_size, x_size + 1, x, x_size) > 0);
-         goto do_sub;
-         }
+         if(z[x_size + j - 1] > x[j-1])
+            break;
 
-      if(z[x_size + j - 1] < x[j-1])
-         {
-         //assert((bigint_cmp(z + x_size, x_size + 1, x, x_size) < 0);
-         goto done;
+         if(z[x_size + j - 1] < x[j-1])
+            return;
          }
       }
 
-   // default to subtraction (equal)
-
-   //assert(m(bigint_cmp(z + x_size, x_size + 1, x, x_size) == 0);
-
-do_sub:
-
-   //bigint_sub2(z + x_size, x_size + 1, x, x_size);
+   /* If the compare above is true, subtract using bigint_sub2 (inlined) */
+   word carry = 0;
+   const u32bit blocks = x_size - (x_size % 8);
 
    for(u32bit j = 0; j != blocks; j += 8)
       carry = word8_sub2(z + x_size + j, x + j, carry);
@@ -191,11 +72,6 @@ do_sub:
 
    if(carry)
       --z[x_size+x_size];
-
-done:
-   return;
-
-#endif
    }
 
 }