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w3rt.cpp
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w3rt.cpp
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// A WebAssembly codebase by Jay Krell
//
// https://webassembly.github.io/spec/core/binary/index.html
// https://webassembly.github.io/spec/core/_download/WebAssembly.pdf
#include "w3.h"
#undef PopulationCount64
#undef PopulationCount32
#if _MSC_VER
extern __forceinline
#endif
uint32_t PopulationCount64 (uint64_t a)
{
//todo intrinsics and portable performance and constant time
uint64_t c = 0;
const uint64_t b = 1;
while (a)
{
c += (a & b);
a >>= 1;
}
return (uint32_t)c;
}
#if _MSC_VER
extern __forceinline
#endif
uint32_t PopulationCount32 (uint32_t a)
{
return PopulationCount64 (a);
}
#if _MSC_VER
extern __forceinline
#endif
uint32_t CountTrailingZeros64 (uint64_t a)
{
//todo intrinsics and portable performance and constant time
uint64_t c = 0;
while ((a & 1) == 0 && c < 64)
{
a >>= 1;
++c;
}
return (uint32_t)c;
}
#if _MSC_VER
extern __forceinline
#endif
uint32_t CountTrailingZeros32 (uint32_t a)
{
uint64_t b = a;
return CountTrailingZeros64 (b) & 31;
}
#if _MSC_VER
extern __forceinline
#endif
uint32_t CountLeadingZeros64 (uint64_t a)
{
//todo intrinsics and portable performance and constant time
uint64_t c = 0;
const uint64_t b = ((uint64_t)1) << 63;
while ((a & b) == 0 && c < 64)
{
a <<= 1;
++c;
}
return (uint32_t)c;
}
#if _MSC_VER
extern __forceinline
#endif
uint32_t CountLeadingZeros32 (uint32_t a)
{
uint64_t b = a;
return CountLeadingZeros64 (b << 32) & 31;
}
#if 0
int main()
{
#define X2(x) printf("%s:%d\n", #x, x);
#define X(x) X2(x(1)); \
X2(x(0)); X2(x(2)); X2(x(3)); X2(x(4)); X2(x(((int64_t)-1))); \
X2(x(((int64_t)1) << 30)); \
X2(x(((int64_t)1) << 33)); \
X2(x(((int64_t)7) << 30)); \
X2(x(((int64_t)7) << 33)); \
X2(x(((int64_t)~0) << 30)); \
X2(x(((int64_t)~0) << 33)); \
X2(x(0x80000000)); \
X2(x(0x70000000)); \
X2(x(0xF0000000)); \
X2(x(0x08000000)); \
X2(x(0x07000000)); \
X2(x(0x0F000000)); \
X2(x(0xF80000000)); \
X2(x(0xF70000000)); \
X2(x(0xFF0000000)); \
X2(x(0xF08000000)); \
X2(x(0xF07000000)); \
X2(x(0xF0F000000)); \
X2(x(((int64_t)-2))); \
X(CountLeadingZeros32);
X(CountLeadingZeros64);
X(CountTrailingZeros32);
X(CountTrailingZeros64);
X(PopulationCount32);
X(PopulationCount64);
}
#endif