tools lib: Sync tools/lib/find_bit.c with the kernel

Need to move the bitmap.[ch] things from tools/perf/ to tools/lib, will
be done in the next patches.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: George Spelvin <linux@horizon.com
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Yury Norov <yury.norov@gmail.com>
Link: http://lkml.kernel.org/n/tip-5fys65wkd7gu8j7a7xgukc5t@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 49 insertions, 54 deletions

diff --git a/tools/lib/find_bit.c b/tools/lib/find_bit.c
index 732d8c38d2c3..9122a9e80046 100644
--- a/tools/lib/find_bit.c
+++ b/tools/lib/find_bit.c
@@ -1,10 +1,17 @@
-/* find_next_bit.c: fallback find next bit implementation
+/* bit search implementation
  *
- * Copied from lib/find_next_bit.c to tools/lib/find_bit.c
+ * Copied from lib/find_bit.c to tools/lib/find_bit.c
  *
  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
+ * Copyright (C) 2008 IBM Corporation
+ * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
+ * (Inspired by David Howell's find_next_bit implementation)
+ *
+ * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
+ * size and improve performance, 2015.
+ *
  * 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
@@ -12,52 +19,50 @@
  */
 
 #include <linux/bitops.h>
-#include <asm/types.h>
-#include <asm/byteorder.h>
+#include <linux/bitmap.h>
+#include <linux/kernel.h>
 
-#define BITOP_WORD(nr)          ((nr) / BITS_PER_LONG)
+#if !defined(find_next_bit)
 
-#ifndef find_next_bit
 /*
- * Find the next set bit in a memory region.
+ * This is a common helper function for find_next_bit and
+ * find_next_zero_bit.  The difference is the "invert" argument, which
+ * is XORed with each fetched word before searching it for one bits.
  */
-unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
-                            unsigned long offset)
+static unsigned long _find_next_bit(const unsigned long *addr,
+                unsigned long nbits, unsigned long start, unsigned long invert)
 {
-        const unsigned long *p = addr + BITOP_WORD(offset);
-        unsigned long result = offset & ~(BITS_PER_LONG-1);
         unsigned long tmp;
 
-        if (offset >= size)
-                return size;
-        size -= result;
-        offset %= BITS_PER_LONG;
-        if (offset) {
-                tmp = *(p++);
-                tmp &= (~0UL << offset);
-                if (size < BITS_PER_LONG)
-                        goto found_first;
-                if (tmp)
-                        goto found_middle;
-                size -= BITS_PER_LONG;
-                result += BITS_PER_LONG;
-        }
-        while (size & ~(BITS_PER_LONG-1)) {
-                if ((tmp = *(p++)))
-                        goto found_middle;
-                result += BITS_PER_LONG;
-                size -= BITS_PER_LONG;
+        if (!nbits || start >= nbits)
+                return nbits;
+
+        tmp = addr[start / BITS_PER_LONG] ^ invert;
+
+        /* Handle 1st word. */
+        tmp &= BITMAP_FIRST_WORD_MASK(start);
+        start = round_down(start, BITS_PER_LONG);
+
+        while (!tmp) {
+                start += BITS_PER_LONG;
+                if (start >= nbits)
+                        return nbits;
+
+                tmp = addr[start / BITS_PER_LONG] ^ invert;
         }
-        if (!size)
-                return result;
-        tmp = *p;
 
-found_first:
-        tmp &= (~0UL >> (BITS_PER_LONG - size));
-        if (tmp == 0UL)         /* Are any bits set? */
-                return result + size;   /* Nope. */
-found_middle:
-        return result + __ffs(tmp);
+        return min(start + __ffs(tmp), nbits);
+}
+#endif
+
+#ifndef find_next_bit
+/*
+ * Find the next set bit in a memory region.
+ */
+unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
+                            unsigned long offset)
+{
+        return _find_next_bit(addr, size, offset, 0UL);
 }
 #endif
 
@@ -67,23 +72,13 @@ found_middle:
  */
 unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
 {
-        const unsigned long *p = addr;
-        unsigned long result = 0;
-        unsigned long tmp;
+        unsigned long idx;
 
-        while (size & ~(BITS_PER_LONG-1)) {
-                if ((tmp = *(p++)))
-                        goto found;
-                result += BITS_PER_LONG;
-                size -= BITS_PER_LONG;
+        for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
+                if (addr[idx])
+                        return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
         }
-        if (!size)
-                return result;
 
-        tmp = (*p) & (~0UL >> (BITS_PER_LONG - size));
-        if (tmp == 0UL)         /* Are any bits set? */
-                return result + size;   /* Nope. */
-found:
-        return result + __ffs(tmp);
+        return size;
 }
 #endif