[Gmp-commit] /var/hg/gmp: New macro udiv_rnnd_preinv

[mercurial at gmplib.org]

details:   /var/hg/gmp/rev/7c2810e5f9d0
changeset: 13917:7c2810e5f9d0
user:      Niels M?ller <nisse at lysator.liu.se>
date:      Sun Feb 27 11:58:15 2011 +0100
description:
New macro udiv_rnnd_preinv

diffstat:

 ChangeLog  |   5 ++++-
 gmp-impl.h |  24 ++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletions(-)

diffs (53 lines):

diff -r 98add4b37ac1 -r 7c2810e5f9d0 ChangeLog
--- a/ChangeLog	Sun Feb 27 00:29:38 2011 +0100
+++ b/ChangeLog	Sun Feb 27 11:58:15 2011 +0100
@@ -1,3 +1,7 @@
+2011-02-27  Niels Möller  <nisse at lysator.liu.se>
+
+	* gmp-impl.h (udiv_rnnd_preinv): New macro.
+
 2011-02-27  Torbjorn Granlund  <tege at gmplib.org>
 
 	* mpn/x86/atom/sse2/mul_basecase.asm: New file.
@@ -35,7 +39,6 @@
 	* mpn/x86/atom/copyd.asm: ReMoved (in mmx/ now).
 	* mpn/x86/atom/copyi.asm: Likewise.
 	* mpn/x86/atom/hamdist.asm: Likewise.
-	
 
 2011-02-24  Torbjorn Granlund  <tege at gmplib.org>
 
diff -r 98add4b37ac1 -r 7c2810e5f9d0 gmp-impl.h
--- a/gmp-impl.h	Sun Feb 27 00:29:38 2011 +0100
+++ b/gmp-impl.h	Sun Feb 27 11:58:15 2011 +0100
@@ -2792,6 +2792,30 @@
     (q) = _qh;								\
   } while (0)
 
+/* Unlike udiv_qrnnd_preinv, works also for nh == d.
+
+   FIXME: The special case for nl = constant 0 could be simplified
+   further, like in udiv_rnd_preinv below. Note that with nl = 0, the
+   case _r >= d can't happen. Also applies to udiv_qrnnd_preinv
+   above.
+
+   FIXME: Use mask for adjustment? */
+#define udiv_rnnd_preinv(r, nh, nl, d, di)				\
+  do {									\
+    mp_limb_t _qh, _ql, _r;						\
+    umul_ppmm (_qh, _ql, (nh), (di));					\
+    if (__builtin_constant_p (nl) && (nl) == 0)				\
+      _qh += (nh) + 1;							\
+    else								\
+      add_ssaaaa (_qh, _ql, _qh, _ql, (nh) + 1, (nl));			\
+    _r = (nl) - _qh * (d);						\
+    if (_r > _ql)	/* both > and >= should be OK */		\
+      _r += (d);							\
+    if (UNLIKELY (_r >= (d)))						\
+      _r -= (d);							\
+    (r) = _r;								\
+  } while (0)
+
 /* Compute r = nh*B mod d, where di is the inverse of d.  */
 #define udiv_rnd_preinv(r, nh, d, di)					\
   do {									\