|
| |
Bit Scan Reverse
|
86/88 |
N |
186 |
N |
286 |
N |
386 |
Y |
486 |
Y |
BSR destination, source |
|
Ovfl |
N |
Dir |
N |
Int |
N |
Trap |
N |
Sign |
N |
Zero |
Y |
Aux |
N |
Prty |
N |
Carry |
N |
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).
------------------------------------ Timing ----------------------------------
OpCode Instruction 386 286 86
0F BD BSR r16, r/m16 10+3n
0F BD BSR r32, r/m32 10+3n
------------------------------------ Logic -----------------------------------
If source = 0 then
ZF = 0
else
ZF = 1
destination = bit index of first bit set
See Also BSF BT BTC BTR BTS SETxx Flags |