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back2root:ibm-pc-ms-dos:instr:bsr

BSR - (386+ only)

BSR - Bit Scan Reverse (386+ only)

Scans source operand for first bit set. Sets ZF if a bit is found set and loads the destination with an index to first set bit. Clears ZF is no bits are found set. BSF scans forward across bit pattern (0-n) while BSR scans in reverse (n-0).

Usage:

	BSR	dest,src	

Modifies flags:

ZF

Clocks Size
Operands 808x 286 386 486 Bytes
reg,reg - - 10+3n 6-103 3
reg,mem - - 10+3n 7-104 3-7
reg32,reg32 - - 10+3n 6-103 3-7
reg32,mem32 - - 10+3n 7-104 3-7
back2root/ibm-pc-ms-dos/instr/bsr.txt · Dernière modification : 2023/03/03 23:53 de 127.0.0.1