6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-21 03:32:21 +00:00
Code Issues Projects Releases Wiki Activity

Use the GCC built-in for PopulationCount when it's available, and use a faster

Browse Source 
algorithm when it's not.  This should be particularly noticeable in the
64-bit case.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34776 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2007-03-01 05:41:28 +00:00
parent af8fb19846
commit 2a934cb607
1 changed files with 16 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
include/llvm/Support/MathExtras.h
View File

@ -208,22 +208,27 @@ inline unsigned CountTrailingZeros_64(uint64_t Value) {
/// CountPopulation_32 - this function counts the number of set bits in a value.
/// Ex. CountPopulation(0xF000F000) = 8
/// Returns 0 if the word is zero.
inline unsigned CountPopulation_32(unsigned Value) {
unsigned x, t;
x = Value - ((Value >> 1) & 0x55555555);
t = ((x >> 2) & 0x33333333);
x = (x & 0x33333333) + t;
x = (x + (x >> 4)) & 0x0F0F0F0F;
x = x + (x << 8);
x = x + (x << 16);
return x >> 24;
inline unsigned CountPopulation_32(uint32_t Value) {
#if __GNUC__ >= 4
return __builtin_popcount(Value);
#else
uint32_t v = v - ((v >> 1) & 0x55555555);
v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
#endif
}
/// CountPopulation_64 - this function counts the number of set bits in a value,
/// (64 bit edition.)
inline unsigned CountPopulation_64(uint64_t Value) {
return CountPopulation_32(unsigned(Value >> 32)) +
CountPopulation_32(unsigned(Value));
#if __GNUC__ >= 4
return __builtin_popcountll(Value);
#else
uint64_t v = Value - ((Value >> 1) & 0x5555555555555555ULL);
v = (v & 0x3333333333333333ULL) + ((v >> 2) & 0x3333333333333333ULL);
v = (v + (v >> 4)) & 0x0F0F0F0F0F0F0F0FULL;
return (uint64_t)(v * 0x0101010101010101ULL) >> 56;
#endif
}
/// Log2_32 - This function returns the floor log base 2 of the specified value,