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Add support for count trailing zeroes, and population count. These are

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needed for folding constants in the upcoming dag combiner.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23163 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nate Begeman 2005-08-31 00:25:01 +00:00
parent eb80fe8ff6
commit 16d6ea5264
1 changed files with 37 additions and 5 deletions
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42
include/llvm/Support/MathExtras.h
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@ -83,10 +83,6 @@ inline bool isPowerOf2_64(uint64_t Value) {
// counting the number of zeros from the most significant bit to the first one // counting the number of zeros from the most significant bit to the first one
// bit. Ex. CountLeadingZeros_32(0x00F000FF) == 8. // bit. Ex. CountLeadingZeros_32(0x00F000FF) == 8.
// Returns 32 if the word is zero. // Returns 32 if the word is zero.
// CountLeadingZeros_32 - this function performs the platform optimal form
// of counting the number of zeros from the most significant bit to the first
// one bit. Ex. CountLeadingZeros_32(0x00F000FF) == 8.
// Returns 32 if the word is zero.
inline unsigned CountLeadingZeros_32(unsigned Value) { inline unsigned CountLeadingZeros_32(unsigned Value) {
unsigned Count; // result unsigned Count; // result
#if __GNUC__ >= 4 #if __GNUC__ >= 4
@ -155,12 +151,48 @@ inline unsigned CountLeadingZeros_64(uint64_t Value) {
return Count; return Count;
} }
// CountTrailingZeros_32 - this function performs the platform optimal form of
// counting the number of zeros from the least significant bit to the first one
// bit. Ex. CountTrailingZeros_32(0xFF00FF00) == 8.
// Returns 32 if the word is zero.
inline unsigned CountTrailingZeros_32(unsigned Value) {
return 32 - CountLeadingZeros_32(~Value & (Value - 1));
}
// CountTrailingZeros_64 - This function performs the platform optimal form
// of counting the number of zeros from the least significant bit to the first
// one bit (64 bit edition.)
// Returns 64 if the word is zero.
inline unsigned CountTrailingZeros_64(uint64_t Value) {
return 64 - CountLeadingZeros_64(~Value & (Value - 1));
}
// 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;
}
// 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(Value >> 32) + CountPopulation_32(Value);
}
// Log2_32 - This function returns the floor log base 2 of the specified value, // Log2_32 - This function returns the floor log base 2 of the specified value,
// -1 if the value is zero. (32 bit edition.) // -1 if the value is zero. (32 bit edition.)
// Ex. Log2_32(32) == 5, Log2_32(1) == 0, Log2_32(0) == -1 // Ex. Log2_32(32) == 5, Log2_32(1) == 0, Log2_32(0) == -1
inline unsigned Log2_32(unsigned Value) { inline unsigned Log2_32(unsigned Value) {
return 31 - CountLeadingZeros_32(Value); return 31 - CountLeadingZeros_32(Value);
} }
// Log2_64 - This function returns the floor log base 2 of the specified value, // Log2_64 - This function returns the floor log base 2 of the specified value,
// -1 if the value is zero. (64 bit edition.) // -1 if the value is zero. (64 bit edition.)