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[Qemu-devel] [PATCH v3] bitops: unify bitops_ffsl with the one in host-u
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From: |
Paolo Bonzini |
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Subject: |
[Qemu-devel] [PATCH v3] bitops: unify bitops_ffsl with the one in host-utils.h, call it bitops_ctzl |
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Date: |
Fri, 1 Feb 2013 23:03:16 +0100 |
We had two copies of a ffs function for longs with subtly different
semantics and, for the one in bitops.h, a confusing name: the result
was off-by-one compared to the library function ffsl.
Unify the functions into one, and solve the name problem by calling
the 0-based functions "bitops_ctzl" and "bitops_ctol" respectively.
This also fixes the build on platforms with ffsl, including Mac OS X
and Windows.
Signed-off-by: Paolo Bonzini <address@hidden>
---
include/qemu/bitops.h | 55 +++++++++++++++++++----------------------------
include/qemu/hbitmap.h | 2 +-
include/qemu/host-utils.h | 26 ----------------------
memory.c | 4 ++--
util/bitops.c | 4 ++--
util/hbitmap.c | 2 +-
6 files changed, 28 insertions(+), 65 deletions(-)
diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h
index 74e14e5..8b88791 100644
--- a/include/qemu/bitops.h
+++ b/include/qemu/bitops.h
@@ -13,6 +13,7 @@
#define BITOPS_H
#include "qemu-common.h"
+#include "host-utils.h"
#define BITS_PER_BYTE CHAR_BIT
#define BITS_PER_LONG (sizeof (unsigned long) * BITS_PER_BYTE)
@@ -23,41 +24,29 @@
#define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
/**
- * bitops_ffs - find first bit in word.
+ * bitops_ctzl - count trailing zeroes in word.
* @word: The word to search
*
- * Undefined if no bit exists, so code should check against 0 first.
+ * Returns -1 if no bit exists. Note that compared to the C library
+ * routine ffsl, this one returns one less.
*/
-static unsigned long bitops_ffsl(unsigned long word)
+static unsigned long bitops_ctzl(unsigned long word)
{
- int num = 0;
+#if QEMU_GNUC_PREREQ(3, 4)
+ return __builtin_ffsl(word) - 1;
+#else
+ if (!word) {
+ return -1;
+ }
-#if LONG_MAX > 0x7FFFFFFF
- if ((word & 0xffffffff) == 0) {
- num += 32;
- word >>= 32;
- }
+ if (sizeof(long) == 4) {
+ return ctz32(word);
+ } else if (sizeof(long) == 8) {
+ return ctz64(word);
+ } else {
+ abort();
+ }
#endif
- if ((word & 0xffff) == 0) {
- num += 16;
- word >>= 16;
- }
- if ((word & 0xff) == 0) {
- num += 8;
- word >>= 8;
- }
- if ((word & 0xf) == 0) {
- num += 4;
- word >>= 4;
- }
- if ((word & 0x3) == 0) {
- num += 2;
- word >>= 2;
- }
- if ((word & 0x1) == 0) {
- num += 1;
- }
- return num;
}
/**
@@ -99,14 +88,14 @@ static inline unsigned long bitops_flsl(unsigned long word)
}
/**
- * ffz - find first zero in word.
+ * cto - count trailing ones in word.
* @word: The word to search
*
- * Undefined if no zero exists, so code should check against ~0UL first.
+ * Returns -1 if all bit are set.
*/
-static inline unsigned long ffz(unsigned long word)
+static inline unsigned long bitops_ctol(unsigned long word)
{
- return bitops_ffsl(~word);
+ return bitops_ctzl(~word);
}
/**
diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h
index 73f5d1d..250de03 100644
--- a/include/qemu/hbitmap.h
+++ b/include/qemu/hbitmap.h
@@ -170,7 +170,7 @@ static inline int64_t hbitmap_iter_next(HBitmapIter *hbi)
/* The next call will resume work from the next bit. */
hbi->cur[HBITMAP_LEVELS - 1] = cur & (cur - 1);
- item = ((uint64_t)hbi->pos << BITS_PER_LEVEL) + ffsl(cur) - 1;
+ item = ((uint64_t)hbi->pos << BITS_PER_LEVEL) + bitops_ctzl(cur);
return item << hbi->granularity;
}
diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index 2a32be4..81c9a75 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -26,7 +26,6 @@
#define HOST_UTILS_H 1
#include "qemu/compiler.h" /* QEMU_GNUC_PREREQ */
-#include <string.h> /* ffsl */
#if defined(__x86_64__)
#define __HAVE_FAST_MULU64__
@@ -238,29 +237,4 @@ static inline int ctpop64(uint64_t val)
#endif
}
-/* glibc does not provide an inline version of ffsl, so always define
- * ours. We need to give it a different name, however.
- */
-#ifdef __GLIBC__
-#define ffsl qemu_ffsl
-#endif
-static inline int ffsl(long val)
-{
- if (!val) {
- return 0;
- }
-
-#if QEMU_GNUC_PREREQ(3, 4)
- return __builtin_ctzl(val) + 1;
-#else
- if (sizeof(long) == 4) {
- return ctz32(val) + 1;
- } else if (sizeof(long) == 8) {
- return ctz64(val) + 1;
- } else {
- abort();
- }
-#endif
-}
-
#endif
diff --git a/memory.c b/memory.c
index 410c5f8..cd7d5e0 100644
--- a/memory.c
+++ b/memory.c
@@ -855,7 +855,7 @@ static uint64_t memory_region_dispatch_read1(MemoryRegion
*mr,
}
if (!mr->ops->read) {
- return mr->ops->old_mmio.read[bitops_ffsl(size)](mr->opaque, addr);
+ return mr->ops->old_mmio.read[bitops_ctzl(size)](mr->opaque, addr);
}
/* FIXME: support unaligned access */
@@ -908,7 +908,7 @@ static void memory_region_dispatch_write(MemoryRegion *mr,
adjust_endianness(mr, &data, size);
if (!mr->ops->write) {
- mr->ops->old_mmio.write[bitops_ffsl(size)](mr->opaque, addr, data);
+ mr->ops->old_mmio.write[bitops_ctzl(size)](mr->opaque, addr, data);
return;
}
diff --git a/util/bitops.c b/util/bitops.c
index 4c3a836..7b853cf 100644
--- a/util/bitops.c
+++ b/util/bitops.c
@@ -60,7 +60,7 @@ found_first:
return result + size; /* Nope. */
}
found_middle:
- return result + bitops_ffsl(tmp);
+ return result + bitops_ctzl(tmp);
}
/*
@@ -109,7 +109,7 @@ found_first:
return result + size; /* Nope. */
}
found_middle:
- return result + ffz(tmp);
+ return result + bitops_ctol(tmp);
}
unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
diff --git a/util/hbitmap.c b/util/hbitmap.c
index 2aa487d..a0df5d3 100644
--- a/util/hbitmap.c
+++ b/util/hbitmap.c
@@ -126,7 +126,7 @@ unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi)
* The index of this word's least significant set bit provides
* the low-order bits.
*/
- pos = (pos << BITS_PER_LEVEL) + ffsl(cur) - 1;
+ pos = (pos << BITS_PER_LEVEL) + bitops_ctzl(cur);
hbi->cur[i] = cur & (cur - 1);
/* Set up next level for iteration. */
--
1.8.1