Developer Guide and Reference



Counts the number of leading zero bits in a source operand. Returns operand size as output when source operand is zero. The corresponding Intel® AVX2 instruction is


extern unsigned int _lzcnt_u32(unsigned int source);
extern unsigned __int64 _lzcnt_u64(unsigned __int64 source);
the source operand used for the operation
Counts the number of leading most significant zero bits in a source operand returning the result into a destination when source operand is 0.
Result of the operation.

Product and Performance Information


Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804