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Bug 327129: Reverting the previous commit as it broke GCC builds of

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firefox.


git-svn-id: svn://10.0.0.236/trunk@190564 18797224-902f-48f8-a5cc-f745e15eee43
This commit is contained in:
igor%mir2.org 2006-02-20 10:12:03 +00:00
parent 4d6c699705
commit 8e1846deea
2 changed files with 26 additions and 35 deletions
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33
mozilla/js/src/jsbit.h
View File

@ -69,21 +69,7 @@ extern JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 i);
** Macro version of JS_CeilingLog2: Compute the log of the least power of
** 2 greater than or equal to _n. The result is returned in _log2.
*/
#ifdef __GNUC__
/*
* Use __builtin_clz or count-leading-zeros to calculate ceil(log2(_n)).
* Since __builtin_clz(0) is undefined, the macro uses explicit conditional.
* FIXME: branch-free version?
*/
# define JS_CEILING_LOG2(_log2,_n) \
JS_BEGIN_MACRO \
typedef int COMPILER_ASSERT##__LINE__[ \
sizeof(unsigned int) == sizeof(JSUint32) ? 1 : -1]; \
unsigned int j_ = (unsigned int)(_n); \
(_log2) = (j_ <= 1 ? 0 : 32 - __builtin_clz(j_ - 1)); \
JS_END_MACRO
#else
# define JS_CEILING_LOG2(_log2,_n) \
#define JS_CEILING_LOG2(_log2,_n) \
JS_BEGIN_MACRO \
JSUint32 j_ = (JSUint32)(_n); \
(_log2) = 0; \
@ -100,7 +86,6 @@ extern JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 i);
if ((j_) >> 1) \
(_log2) += 1; \
JS_END_MACRO
#endif
/*
** Macro version of JS_FloorLog2: Compute the log of the greatest power of
@ -108,20 +93,7 @@ extern JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 i);
**
** This is equivalent to finding the highest set bit in the word.
*/
#ifdef __GNUC__
/*
* Use __builtin_clz or count-leading-zeros to calculate floor(log2(_n)).
* Since __builtin_clz(0) is undefined, the macro set the loweset bit to 1
* to ensure 0 result when _n == 0.
*/
# define JS_FLOOR_LOG2(_log2,_n) \
JS_BEGIN_MACRO \
typedef int COMPILER_ASSERT##__LINE__[ \
sizeof(unsigned int) == sizeof(JSUint32) ? 1 : -1]; \
(_log2) = 31 - __builtin_clz(((unsigned int)(_n)) | 1); \
JS_END_MACRO
#else
# define JS_FLOOR_LOG2(_log2,_n) \
#define JS_FLOOR_LOG2(_log2,_n) \
JS_BEGIN_MACRO \
JSUint32 j_ = (JSUint32)(_n); \
(_log2) = 0; \
@ -136,7 +108,6 @@ extern JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 i);
if ((j_) >> 1) \
(_log2) += 1; \
JS_END_MACRO
#endif
JS_END_EXTERN_C
#endif /* jsbit_h___ */

28
mozilla/js/src/jslog2.c
View File

@ -44,9 +44,20 @@
*/
JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 n)
{
JSIntn log2;
JSIntn log2 = 0;
JS_CEILING_LOG2(log2, n);
if (n & (n-1))
log2++;
if (n >> 16)
log2 += 16, n >>= 16;
if (n >> 8)
log2 += 8, n >>= 8;
if (n >> 4)
log2 += 4, n >>= 4;
if (n >> 2)
log2 += 2, n >>= 2;
if (n >> 1)
log2++;
return log2;
}
@ -56,8 +67,17 @@ JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 n)
*/
JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 n)
{
JSIntn log2;
JSIntn log2 = 0;
JS_FLOOR_LOG2(log2, n);
if (n >> 16)
log2 += 16, n >>= 16;
if (n >> 8)
log2 += 8, n >>= 8;
if (n >> 4)
log2 += 4, n >>= 4;
if (n >> 2)
log2 += 2, n >>= 2;
if (n >> 1)
log2++;
return log2;
}