1 files changed, 59 insertions, 0 deletions

diff --git a/firmware/asm/mips/ffs.S b/firmware/asm/mips/ffs.S
new file mode 100644
index 0000000000..a2a82a6a32
--- /dev/null
+++ b/firmware/asm/mips/ffs.S
@@ -0,0 +1,59 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2009 by Maurus Cuelenaere
+ * based on ffs-arm.S by Michael Sevakis
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#include "config.h"
+#include "mips.h"
+
+/****************************************************************************
+ * int find_first_set_bit(uint32_t val);
+ *
+ * Find the index of the least significant set bit in the 32-bit word.
+ *
+ * return values:
+ *   0  - bit 0 is set
+ *   1  - bit 1 is set
+ *   ...
+ *   31 - bit 31 is set
+ *   32 - no bits set
+ ****************************************************************************/
+    .align  2
+    .global find_first_set_bit
+    .type   find_first_set_bit, %function
+    .set    noreorder
+    .set    noat
+    
+find_first_set_bit:
+    beqz    a0, l                    # if(a0 == 0) goto l
+    nop                              #
+    negu    t0, a0                   # t0 = -a0
+    and     t0, a0, t0               # t0 = a0 & t0
+    clz     v0, t0                   # get lead 0's count
+    li      t0, 31                   # t0 = 31
+    jr      ra                       #
+    subu    v0, t0, v0               # v0 = t0 - v0
+
+l:
+    jr      ra                       #
+    li      v0, 32                   # v0 = 32
+    
+    .set    reorder
+    .set    at