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Fixed findMSB generic path

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This commit is contained in:
Christophe Riccio 2012-09-13 00:43:46 +02:00
parent a2ba0ea86f
commit 8a7d6080d1
2 changed files with 138 additions and 35 deletions
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90
glm/core/func_integer.inl
View File

@ -522,39 +522,9 @@ namespace glm
}
// findMSB
/*
#if((GLM_ARCH != GLM_ARCH_PURE) && (GLM_COMPILER & GLM_COMPILER_VC))
template <typename genIUType>
GLM_FUNC_QUALIFIER int findMSB
(
genIUType const & Value
)
{
unsigned long Result(0);
_BitScanReverse(&Result, Value);
return int(Result);
}
#elif((GLM_ARCH != GLM_ARCH_PURE) && (GLM_COMPILER & GLM_COMPILER_GCC) && (GLM_COMPILER >= GLM_COMPILER_GCC40))
template <typename genIUType>
GLM_FUNC_QUALIFIER int findMSB
(
genIUType const & Value
)
{
/**
* clz returns the number or trailing 0-bits; see
* http://gcc.gnu.org/onlinedocs/gcc-4.7.1/gcc/Other-Builtins.html
*
* NoteBecause __builtin_clz only works for unsigned ints, this
* implementation will not work for 64-bit integers.
*/
return 31 - __builtin_clz(Value);
}
#else
template <typename genIUType>
GLM_FUNC_QUALIFIER int findMSB
(
@ -565,11 +535,61 @@ namespace glm
if(Value == 0)
return -1;
genIUType bit = genIUType(-1);
for(genIUType tmp = Value; tmp; tmp >>= 1, ++bit){}
return bit;
unsigned long Result(0);
_BitScanReverse(&Result, Value);
return int(Result);
}
#endif//(GLM_COMPILER)
// __builtin_clz seems to be buggy as it crasks for some values, from 0x00200000 to 80000000
#elif((GLM_ARCH != GLM_ARCH_PURE) && (GLM_COMPILER & GLM_COMPILER_GCC) && (GLM_COMPILER >= GLM_COMPILER_GCC40))
template <typename genIUType>
GLM_FUNC_QUALIFIER int findMSB
(
genIUType const & Value
)
{
GLM_STATIC_ASSERT(std::numeric_limits<genIUType>::is_integer, "'findMSB' only accept integer values");
if(Value == 0)
return -1;
// clz returns the number or trailing 0-bits; see
// http://gcc.gnu.org/onlinedocs/gcc-4.7.1/gcc/Other-Builtins.html
//
// NoteBecause __builtin_clz only works for unsigned ints, this
// implementation will not work for 64-bit integers.
//
return 31 - __builtin_clzl(Value);
}
#else
*/
template <typename genIUType>
GLM_FUNC_QUALIFIER int findMSB
(
genIUType const & Value
)
{
GLM_STATIC_ASSERT(std::numeric_limits<genIUType>::is_integer, "'findMSB' only accept integer values");
if(Value == 0 || Value == -1)
return -1;
else if(Value > 0)
{
genIUType Bit = genIUType(-1);
for(genIUType tmp = Value; tmp > 0; tmp >>= 1, ++Bit){}
return Bit;
}
else //if(Value < 0)
{
int const BitCount(sizeof(genIUType) * 8);
int MostSignificantBit(-1);
for(int BitIndex(0); BitIndex < BitCount; ++BitIndex)
MostSignificantBit = (Value & (1 << BitIndex)) ? MostSignificantBit : BitIndex;
assert(MostSignificantBit >= 0);
return MostSignificantBit;
}
}
//#endif//(GLM_COMPILER)
template <typename T>
GLM_FUNC_QUALIFIER detail::tvec2<int> findMSB

83
test/core/core_func_integer.cpp
View File

@ -125,6 +125,87 @@ namespace bitfieldReverse
}
}//bitRevert
namespace findMSB
{
template <typename genType>
struct type
{
genType Value;
genType Return;
};
type<int> const DataI32[] =
{
{0x00000000, -1},
{0x00000001, 0},
{0x00000002, 1},
{0x00000003, 1},
{0x00000004, 2},
{0x00000005, 2},
{0x00000007, 2},
{0x00000008, 3},
{0x00000010, 4},
{0x00000020, 5},
{0x00000040, 6},
{0x00000080, 7},
{0x00000100, 8},
{0x00000200, 9},
{0x00000400, 10},
{0x00000800, 11},
{0x00001000, 12},
{0x00002000, 13},
{0x00004000, 14},
{0x00008000, 15},
{0x00010000, 16},
{0x00020000, 17},
{0x00040000, 18},
{0x00080000, 19},
{0x00100000, 20},
{0x00200000, 21},
{0x00400000, 22},
{0x00800000, 23},
{0x01000000, 24},
{0x02000000, 25},
{0x04000000, 26},
{0x08000000, 27},
{0x10000000, 28},
{0x20000000, 29},
{0x40000000, 30},
{0x80000000, 30},
{0xffffffff, -1},
{0xfffffffe, 0},
{0xfffffffd, 1},
{0xfffffffc, 1},
{0xfffffffb, 2},
{0xfffffffa, 2},
{0xfffffff0, 3}
};
int test()
{
int Error(0);
for(std::size_t i = 0; i < sizeof(DataI32) / sizeof(type<int>); ++i)
{
int Result = glm::findMSB(DataI32[i].Value);
Error += DataI32[i].Return == Result ? 0 : 1;
assert(!Error);
}
return Error;
}
}//findMSB
namespace findLSB
{
int test()
{
int Error(0);
return Error;
}
}//findLSB
int main()
{
int Error = 0;
@ -133,6 +214,8 @@ int main()
Error += ::bitfieldExtract::test();
Error += ::bitfieldReverse::test();
Error += ::findMSB::test();
Error += ::findLSB::test();
return Error;
}