[src/trunk]: src/lib/libc/arch/x86_64/gen add a simpler version.

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

details:   https://anonhg.NetBSD.org/src/rev/f4950de8fa4f
branches:  trunk
changeset: 769998:f4950de8fa4f
user:      christos <christos%NetBSD.org@localhost>
date:      Thu Sep 29 22:45:20 2011 +0000

description:
add a simpler version.

diffstat:

 lib/libc/arch/x86_64/gen/flt_rounds.S |  35 +++++++++++++----------------------
 1 files changed, 13 insertions(+), 22 deletions(-)

diffs (46 lines):

diff -r d6a8b770ecdd -r f4950de8fa4f lib/libc/arch/x86_64/gen/flt_rounds.S
--- a/lib/libc/arch/x86_64/gen/flt_rounds.S     Thu Sep 29 20:59:27 2011 +0000
+++ b/lib/libc/arch/x86_64/gen/flt_rounds.S     Thu Sep 29 22:45:20 2011 +0000
@@ -1,29 +1,20 @@
-/*     $NetBSD: flt_rounds.S,v 1.3 2011/09/28 15:11:42 christos Exp $  */
-
-/*
- * Written by J.T. Conklin, Apr 4, 1995
- * Public domain.
- */
+/*     $NetBSD: flt_rounds.S,v 1.4 2011/09/29 22:45:20 christos Exp $  */
 
 #include <machine/asm.h>
 
+/*
+ * 00 0 round to zero 
+ * 01 1 round to nearest
+ * 10 2 round to positive infinity
+ * 11 3 round to negative infinity
+ */
        .text
        _ALIGN_TEXT
-_map:
-       .byte 1         /* round to nearest */
-       .byte 3         /* round to negative infinity */
-       .byte 2         /* round to positive infinity */
-       .byte 0         /* round to zero */
-
 ENTRY(__flt_rounds)
-       fnstcw -4(%rsp)
-       movl -4(%rsp),%eax
-       shrl $10,%eax
-       andl $3,%eax
-#ifdef PIC
-       leaq _map(%rip),%rcx
-       movb (%rcx,%rax,1),%al
-#else
-       movb _map(,%rax,1),%al
-#endif
+       fnstcw  -4(%rsp)
+       movl    -4(%rsp), %ecx
+       shrl    $9, %ecx
+       andl    $6, %ecx
+       xorl    $1, %eax        /* map 0,1,2,3 -> 1,0,3,2 */
+       andl    $3, %eax
        ret