From 8ff32af323eb3c6554a3495c01cc43ba089d36d5 Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Sun, 28 Oct 2018 22:51:57 +0000
Subject: [PATCH] symm/blkc.h: Define a new `BLKC_ADD' macro.

And rewrite `BLKC_STEP' in terms of it.
---
 symm/blkc.h | 40 ++++++++++++++++++++++++++++++----------
 1 file changed, 30 insertions(+), 10 deletions(-)

diff --git a/symm/blkc.h b/symm/blkc.h
index 608dfcd0..5e996e8b 100644
--- a/symm/blkc.h
+++ b/symm/blkc.h
@@ -95,9 +95,11 @@
   BLKC_GLUE(BLKC_XMOVE_, BLKC_TYPE(PRE))				\
     (PRE, w, wx, BLKC_BITS(PRE))
 
-#define BLKC_STEP(PRE, w)						\
-  BLKC_GLUE(BLKC_STEP_X_, BLKC_ENDIAN(PRE))				\
-    (PRE, w)
+#define BLKC_STEP(PRE, w) BLKC_ADD(PRE, w, 1)
+
+#define BLKC_ADD(PRE, w, n)						\
+  BLKC_GLUE(BLKC_ADD_X_, BLKC_ENDIAN(PRE))				\
+    (PRE, w, n)
 
 #define BLKC_ZERO(PRE, w)						\
   BLKC_GLUE(BLKC_ZERO_, BLKC_TYPE(PRE))					\
@@ -113,6 +115,24 @@
   fputc('\n', stdout);							\
 } while (0)
 
+/* --- Utilities --- *
+ *
+ * These seem too hard to properly generalize, or I'd have put them in
+ * <mLib/bits.h>.
+ */
+
+#ifdef HAVE_UINT64
+#  define BLKC_ADDC32(z_out, c_out, x, y) do {				\
+     uint64 _t = (uint64)(x) + (y);					\
+     (z_out) = U32(_t); (c_out) = _t >> 32;				\
+   } while (0)
+#else
+#  define BLKC_ADDC32(z_out, c_out, x, y) do {				\
+     uint32 _x = (x), _c = 0, _t;					\
+     _t = U32(_x + (y)); (z_out) = _t; (c_out) = (_t < _x);		\
+   } while (0)
+#endif
+
 /* --- General implementation skeleton --- */
 
 #define BLKC_SKEL(PRE, decl, guts) do {					\
@@ -159,15 +179,15 @@
 #define BLKC_ZERO_X(PRE, w, n)						\
   BLKC_SKEL_X(PRE, BLKC_W(w);, *_w++ = 0;)
 
-#define BLKC_STEP_X_B(PRE, w) do {					\
-  unsigned _i = PRE##_BLKSZ/4; BLKC_W(w); uint32 _x = 0;		\
-  while (_i && !_x) { _i--; _w[_i] = _x = U32(_w[_i] + 1); }		\
+#define BLKC_ADD_X_B(PRE, w, n) do {					\
+  unsigned _i = PRE##_BLKSZ/4; BLKC_W(w); uint32 _n = (n);		\
+  while (_i-- && _n) BLKC_ADDC32(_w[_i], _n, _w[_i], _n);		\
 } while (0)
 
-#define BLKC_STEP_X_L(PRE, w) do {					\
-  unsigned _i = 0; BLKC_W(w); uint32 _x = 0;				\
-  while (_i < PRE##_BLKSZ/4 && !_x)					\
-    { _w[_i] = _x = U32(_w[_i] + 1); _i++; }				\
+#define BLKC_ADD_X_L(PRE, w, n) do {					\
+  unsigned _i = 0; BLKC_W(w); uint32 _n = (n);				\
+  while (_i < PRE##_BLKSZ/4 && _n)					\
+    { BLKC_ADDC32(_w[_i], _n, _w[_i], _n); _i++; }			\
 } while (0)
 
 #define BLKC_SET_X_B(PRE, w, x) do {					\
-- 
2.11.0