Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1339

BSR—Bit Scan Reverse
Opcode
0F BD
0F BD
Description
Searches the source operand (second operand) for the most significant set bit (1 bit). If
a most significant 1 bit is found, its bit index is stored in the destination operand (first
operand). The source operand can be a register or a memory location; the destination
operand is a register. The bit index is an unsigned offset from bit 0 of the source
operand. If the contents source operand are 0, the contents of the destination operand
is undefined.
Operation
IF SRC = 0
THEN
ZF  1;
DEST is undefined;
ELSE
ZF  0;
temp  OperandSize - 1;
WHILE Bit(SRC, temp) = 0
DO
temp  temp  1;
DEST  temp;
OD;
FI;
Flags Affected
The ZF flag is set to 1 if all the source operand is 0; otherwise, the ZF flag is cleared.
The CF, OF, SF, AF, and PF, flags are undefined.
Additional Itanium System Environment Exceptions
Itanium Reg Faults NaT Register Consumption Abort.
Itanium Mem FaultsVHPT Data Fault, Nested TLB Fault, Data TLB Fault, Alternate Data
Volume 4: Base IA-32 Instruction Reference
Instruction
BSR r16,r/m16
BSR r32,r/m32
TLB Fault, Data Page Not Present Fault, Data NaT Page Consumption
Abort, Data Key Miss Fault, Data Key Permission Fault, Data Access
Rights Fault, Data Access Bit Fault, Data Dirty Bit Fault
Description
Bit scan reverse on r/m16
Bit scan reverse on r/m32
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