모두의 코드
POPCNT (Intel x86/64 assembly instruction)
POPCNT
Return the Count of Number of Bits Set to 1
참고 사항
아래 표를 해석하는 방법은 x86-64 명령어 레퍼런스 읽는 법 글을 참조하시기 바랍니다.
Opcode | Instruction | Op/ | 64-Bit | Compat/ | Description |
---|---|---|---|---|---|
F3 0F B8 /r | POPCNT r16 r/m16 | RM | Valid | Valid | POPCNT on r/m16 |
F3 0F B8 /r | POPCNT r32 r/m32 | RM | Valid | Valid | POPCNT on r/m32 |
F3 REX.W 0F B8 /r | POPCNT r64 r/m64 | RM | Valid | N.E. | POPCNT on r/m64 |
Instruction Operand Encoding
Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
---|---|---|---|---|
RM | ModRM:reg (w) | ModRM:r/m (r) | NA | NA |
Description
This instruction calculates the number of bits set to 1 in the second operand (source) and returns the count in the first operand (a destination register).
Operation
Count = 0; For (i=0; i < OperandSize; i++) { IF (SRC[ i] = 1) // i'th bit THEN Count++; FI; } DEST <- Count;
Flags Affected
OF, SF, ZF, AF, CF, PF are all cleared. ZF is set if SRC = 0, otherwise ZF is cleared.
Intel C/C++ Compiler Intrinsic Equivalent
POPCNT : int _mm_popcnt_u32(unsigned int a); POPCNT : int64_t _mm_popcnt_u64(unsigned __int64 a);
Protected Mode Exceptions
#GP(0)
If a memory operand effective address is outside the CS, DS, ES, FS or GS segments.
#SS(0)
If a memory operand effective address is outside the SS segment limit.
#PF
(fault-code) For a page fault.
#AC(0)
If an unaligned memory reference is made while the current privilege level is 3 and alignment checking is enabled.
#UD
If CPUID.01H:ECX.POPCNT [Bit 23] = 0.
If LOCK prefix is used.
Real-Address Mode Exceptions
#GP(0)
If any part of the operand lies outside of the effective address space from 0 to 0FFFFH.
#SS(0)
If a memory operand effective address is outside the SS segment limit.
#UD
If CPUID.01H:ECX.POPCNT [Bit 23] = 0.
If LOCK prefix is used.
Virtual 8086 Mode Exceptions
#GP(0) If any part of the operand lies outside of the effective address space from 0 to 0FFFFH.
#SS(0) If a memory operand effective address is outside the SS segment limit.
#PF (fault-code) For a page fault.
#AC(0) If an unaligned memory reference is made while alignment checking is enabled.
#UD If CPUID.01H:ECX.POPCNT [Bit 23] = 0.
If LOCK prefix is used.
Compatibility Mode Exceptions
Same exceptions as in Protected Mode.
64-Bit Mode Exceptions
#GP(0)
If the memory address is in a non-canonical form.
#SS(0)
If a memory address referencing the SS segment is in a non-canonical form.
#PF
(fault-code) For a page fault.
#AC(0)
If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.
#UD
If CPUID.01H:ECX.POPCNT [Bit 23] = 0.
If LOCK prefix is used.

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