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Add support for count trailing zeroes, and population count. These are
needed for folding constants in the upcoming dag combiner. llvm-svn: 23163
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@ -83,10 +83,6 @@ inline bool isPowerOf2_64(uint64_t Value) {
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// counting the number of zeros from the most significant bit to the first one
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// bit. Ex. CountLeadingZeros_32(0x00F000FF) == 8.
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// Returns 32 if the word is zero.
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// CountLeadingZeros_32 - this function performs the platform optimal form
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// of counting the number of zeros from the most significant bit to the first
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// one bit. Ex. CountLeadingZeros_32(0x00F000FF) == 8.
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// Returns 32 if the word is zero.
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inline unsigned CountLeadingZeros_32(unsigned Value) {
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unsigned Count; // result
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#if __GNUC__ >= 4
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@ -155,12 +151,48 @@ inline unsigned CountLeadingZeros_64(uint64_t Value) {
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return Count;
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}
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// CountTrailingZeros_32 - this function performs the platform optimal form of
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// counting the number of zeros from the least significant bit to the first one
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// bit. Ex. CountTrailingZeros_32(0xFF00FF00) == 8.
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// Returns 32 if the word is zero.
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inline unsigned CountTrailingZeros_32(unsigned Value) {
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return 32 - CountLeadingZeros_32(~Value & (Value - 1));
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}
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// CountTrailingZeros_64 - This function performs the platform optimal form
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// of counting the number of zeros from the least significant bit to the first
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// one bit (64 bit edition.)
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// Returns 64 if the word is zero.
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inline unsigned CountTrailingZeros_64(uint64_t Value) {
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return 64 - CountLeadingZeros_64(~Value & (Value - 1));
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}
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// CountPopulation_32 - this function counts the number of set bits in a value.
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// Ex. CountPopulation(0xF000F000) = 8
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// Returns 0 if the word is zero.
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inline unsigned CountPopulation_32(unsigned Value) {
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unsigned x, t;
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x = Value - ((Value >> 1) & 0x55555555);
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t = ((x >> 2) & 0x33333333);
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x = (x & 0x33333333) + t;
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x = (x + (x >> 4)) & 0x0F0F0F0F;
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x = x + (x << 8);
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x = x + (x << 16);
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return x >> 24;
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}
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// CountPopulation_64 - this function counts the number of set bits in a value,
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// (64 bit edition.)
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inline unsigned CountPopulation_64(uint64_t Value) {
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return CountPopulation_32(Value >> 32) + CountPopulation_32(Value);
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}
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// Log2_32 - This function returns the floor log base 2 of the specified value,
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// -1 if the value is zero. (32 bit edition.)
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// Ex. Log2_32(32) == 5, Log2_32(1) == 0, Log2_32(0) == -1
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inline unsigned Log2_32(unsigned Value) {
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return 31 - CountLeadingZeros_32(Value);
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}
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}
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// Log2_64 - This function returns the floor log base 2 of the specified value,
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// -1 if the value is zero. (64 bit edition.)
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