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Count packed bytes used by a constant map.

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This commit is contained in:
Ben Vanik
2016-02-18 01:06:28 -08:00
parent 5ab0af9e6d
commit 618ca80011
3 changed files with 45 additions and 5 deletions
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16
src/xenia/base/math.h
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@@ -64,6 +64,22 @@ constexpr uint32_t select_bits(uint32_t value, uint32_t a, uint32_t b) {
return (value & make_bitmask(a, b)) >> a;
}
inline uint32_t bit_count(uint32_t v) {
v = v - ((v >> 1) & 0x55555555);
v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
}
inline uint32_t bit_count(uint64_t v) {
v = (v & 0x5555555555555555LU) + (v >> 1 & 0x5555555555555555LU);
v = (v & 0x3333333333333333LU) + (v >> 2 & 0x3333333333333333LU);
v = v + (v >> 4) & 0x0F0F0F0F0F0F0F0FLU;
v = v + (v >> 8);
v = v + (v >> 16);
v = v + (v >> 32) & 0x0000007F;
return static_cast<uint32_t>(v);
}
// lzcnt instruction, typed for integers of all sizes.
// The number of leading zero bits in the value parameter. If value is zero, the
// return value is the size of the input operand (8, 16, 32, or 64). If the most