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专利名称：APPARATUS AND METHOD FOR EXECUTING
FAST BIT SCAN FORWARD/REVERSE(BSR/BSF) INSTRUCTIONS
发明人：Bryan Wayne Pogor申请号：US12582907申请日：20091021
公开号：US20110016296A1公开日：20110120
专利附图：
摘要：An apparatus executes a bit scan instruction that specifies an N-byte inputoperand. A first encoder forward bit scan encodes each input byte to generate N first bit
vectors. A zero detector zero-detects each input byte to generate a second bit vector. Asecond encoder forward bit scan encodes the second bit vector to generate a third bitvector. An N:1 multiplexor, controlled by the third bit vector, selects one of the N first bitvectors to output a fourth bit vector. The apparatus concatenates the third and fourth bitvectors into a fifth bit vector that indicates the bit index of the least significant set bit ofthe input operand. A third encoder forward bit scan encodes a bit-reversed version ofeach input by to generate N sixth bit vectors. A fourth encoder forward bit scan encodesa bit-reversed version of the second bit vector to generate a seventh bit vector. A secondN:1 multiplexor, controlled by the seventh bit vector, selects one of the N sixth bitvectors to output an eighth bit vector. Selection logic selects a concatenation of the thirdand fourth bit vectors into the fifth bit vector if an input indicates forward bit scan, andthe selection logic selects an inverted version of a concatenation of the seventh andeighth bit vectors into the fifth bit vector if the input indicates reverse bit scan.
申请人：Bryan Wayne Pogor
地址：Round Rock TX US
国籍：US
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