[src/trunk]: src/sys/arch/m68k/fpe Rewrite around BFFFO inline asm.

[isaki <isaki%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3f9466c1e9cb
branches:  trunk
changeset: 786223:3f9466c1e9cb
user:      isaki <isaki%NetBSD.org@localhost>
date:      Sat Apr 20 09:32:28 2013 +0000

description:
Rewrite around BFFFO inline asm.
o Prepare C version of BFFFO (from XM6i).
  It is helpful in running FPE on other platforms (for example, for a
  test).  It is also helpful in porting to non-m68k 3rd party :)
o A BFFFO is supported on 68020 or later (though I'm not sure whether
  sun2/68010 uses this FPE correctly or not).

diffstat:

 sys/arch/m68k/fpe/fpu_subr.c |  27 +++++++++++++++++++++++----
 1 files changed, 23 insertions(+), 4 deletions(-)

diffs (62 lines):

diff -r 701adae235f3 -r 3f9466c1e9cb sys/arch/m68k/fpe/fpu_subr.c
--- a/sys/arch/m68k/fpe/fpu_subr.c      Sat Apr 20 09:26:23 2013 +0000
+++ b/sys/arch/m68k/fpe/fpu_subr.c      Sat Apr 20 09:32:28 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: fpu_subr.c,v 1.10 2013/03/26 11:30:21 isaki Exp $ */
+/*     $NetBSD: fpu_subr.c,v 1.11 2013/04/20 09:32:28 isaki Exp $ */
 
 /*
  * Copyright (c) 1992, 1993
@@ -45,7 +45,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: fpu_subr.c,v 1.10 2013/03/26 11:30:21 isaki Exp $");
+__KERNEL_RCSID(0, "$NetBSD: fpu_subr.c,v 1.11 2013/04/20 09:32:28 isaki Exp $");
 
 #include <sys/types.h>
 #include <sys/systm.h>
@@ -56,6 +56,25 @@
 #include "fpu_arith.h"
 
 /*
+ * m68020 or later has a BFFFO instruction, therefore use it.
+ * Otherwise, use C version.
+ */
+static inline int
+bfffo(uint32_t src)
+{
+       int offset;
+#if defined(__m68k__) && !defined(M68010)
+       __asm volatile("bfffo %1{#0:#32},%0" : "=d"(offset) : "g"(src));
+#else
+       int width = 32;
+       for (offset = 0; width-- > 0 && (int)src >= 0; src <<= 1) {
+               offset++;
+       }
+#endif
+       return offset;
+}
+
+/*
  * Shift the given number right rsh bits.  Any bits that `fall off' will get
  * shoved into the sticky field; we return the resulting sticky.  Note that
  * shifting NaNs is legal (this will never shift all bits out); a NaN's
@@ -165,7 +184,7 @@
                 * We have a supernormal number.  We need to shift it right.
                 * We may assume m2==0.
                 */
-               __asm volatile("bfffo %1{#0:#32},%0" : "=d"(rsh) : "g"(m0));
+               rsh = bfffo(m0);
                rsh = 31 - rsh - FP_LG;
                exp += rsh;
                lsh = 32 - rsh;
@@ -177,7 +196,7 @@
                 * We have a regular denorm (a subnormal number), and need
                 * to shift it left.
                 */
-               __asm volatile("bfffo %1{#0:#32},%0" : "=d"(lsh) : "g"(m0));
+               lsh = bfffo(m0);
                lsh = FP_LG - 31 + lsh;
                exp -= lsh;
                rsh = 32 - lsh;