[PATCH 40/59] tools lib: Sync tools/lib/find_bit.c with the kernel

[Arnaldo Carvalho de Melo]

From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

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@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: George Spelvin <linux@xxxxxxxxxxx
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Yury Norov <yury.norov@xxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-5fys65wkd7gu8j7a7xgukc5t@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/lib/find_bit.c                   | 103 ++++++++++++++++-----------------
 tools/perf/util/include/linux/bitmap.h |   2 +
 2 files changed, 51 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@xxxxxxxxxx)
  *
+ * Copyright (C) 2008 IBM Corporation
+ * 'find_last_bit' is written by Rusty Russell <rusty@xxxxxxxxxxxxxxx>
+ * (Inspired by David Howell's find_next_bit implementation)
+ *
+ * Rewritten by Yury Norov <yury.norov@xxxxxxxxx> 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
diff --git a/tools/perf/util/include/linux/bitmap.h b/tools/perf/util/include/linux/bitmap.h
index 40bd21488032..28f5493da491 100644
--- a/tools/perf/util/include/linux/bitmap.h
+++ b/tools/perf/util/include/linux/bitmap.h
@@ -11,6 +11,8 @@ int __bitmap_weight(const unsigned long *bitmap, int bits);
 void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
 		 const unsigned long *bitmap2, int bits);
 
+#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
+
 #define BITMAP_LAST_WORD_MASK(nbits)					\
 (									\
 	((nbits) % BITS_PER_LONG) ?					\
-- 
2.1.0