u3: further optimizes +peg jet

urbit · Oct 13, 2023 · de74b25 · de74b25
1 parent 2d696e3
commit de74b25
Showing 1 changed file with 31 additions and 19 deletions.
diff --git a/pkg/noun/jets/c/peg.c b/pkg/noun/jets/c/peg.c
@@ -6,33 +6,47 @@
 u3_noun
 u3qc_peg(u3_atom a, u3_atom b)
 {
-  if ( 1 == b ) {
+  if ( (0 == a) || (0 == b) ) {
+    return u3m_bail(c3__exit);
+  }
+  else if ( 1 == b ) {
     return u3k(a);
   }
 
-  c3_w  c_w = u3r_met(0, b) - 1;
+  c3_d a_d, b_d;
+  c3_w c_w;
 
-  if ( (c3y == u3a_is_cat(a) && (c3y == u3a_is_cat(b))) ) {
-    c3_w d_w = b - (1 << c_w);
-    c3_d e_d = (c3_d)a << c_w;
-    return u3i_chub(d_w + e_d);
+  if ( (c3y == u3a_is_cat(a)) && (c3y == u3a_is_cat(b)) ) {
+    c_w = c3_bits_word(b) - 1;
+    a_d = a;
+    b_d = b;
   }
   else {
-    u3_atom d, e, f, g, h;
+    c3_w d_w = u3r_met(0, a);
+    c3_d e_d;
+
+    c_w = u3r_met(0, b) - 1;
+    e_d = (c3_d)c_w + d_w;
 
-    d = u3i_word(c_w);
-    e = u3qc_lsh(0, d, 1);
-    f = u3qa_sub(b, e);
-    g = u3qc_lsh(0, d, a);
-    h = u3qa_add(f, g);
+    if ( 64 <= e_d ) {
+      u3i_slab sab_u;
+      u3i_slab_init(&sab_u, 0, e_d);
 
-    u3z(d);
-    u3z(e);
-    u3z(f);
-    u3z(g);
+      u3r_chop(0, 0, c_w,   0, sab_u.buf_w, b);
+      u3r_chop(0, 0, d_w, c_w, sab_u.buf_w, a);
 
-    return h;
+      return u3i_slab_moot(&sab_u);
+    }
+
+    a_d = u3r_chub(0, a);
+    b_d = u3r_chub(0, b);
   }
+
+  b_d  &= ((c3_d)1 << c_w) - 1;
+  a_d <<= c_w;
+  a_d  ^= b_d;
+
+  return u3i_chub(a_d);
 }
 
 u3_noun
@@ -41,8 +55,6 @@ u3wc_peg(u3_noun cor)
   u3_noun a, b;
 
   if ( (c3n == u3r_mean(cor, u3x_sam_2, &a, u3x_sam_3, &b, 0)) ||
-       (0 == a) ||
-       (0 == b) ||
        (c3n == u3ud(b)) ||
        (c3n == u3ud(a) && b != 1) )
   {