_interlockedbittestandreset intrinsic functions

Article
08/03/2021

Microsoft Specific

Generates an instruction to set bit b of the address a to zero and return its original value.

Syntax

unsigned char _interlockedbittestandreset(
   long *a,
   long b
);
unsigned char _interlockedbittestandreset_acq(
   long *a,
   long b
);
unsigned char _interlockedbittestandreset_HLEAcquire(
   long *a,
   long b
);
unsigned char _interlockedbittestandreset_HLERelease(
   long *a,
   long b
);
unsigned char _interlockedbittestandreset_nf(
   long *a,
   long b
);
unsigned char _interlockedbittestandreset_rel(
   long *a,
   long b
);
unsigned char _interlockedbittestandreset64(
   __int64 *a,
   __int64 b
);
unsigned char _interlockedbittestandreset64_acq(
   __int64 *a,
   __int64 b
);
unsigned char _interlockedbittestandreset64_nf(
   __int64 *a,
   __int64 b
);
unsigned char _interlockedbittestandreset64_rel(
   __int64 *a,
   __int64 b
);
unsigned char _interlockedbittestandreset64_HLEAcquire(
   __int64 *a,
   __int64 b
);
unsigned char _interlockedbittestandreset64_HLERelease(
   __int64 *a,
   __int64 b
);

Parameters

a
[in] A pointer to the memory to examine.

b
[in] The bit position to test.

Return value

The original value of the bit at the position specified by b.

Requirements

Intrinsic	Architecture	Header
`_interlockedbittestandreset`	x86, ARM, x64, ARM64	<intrin.h>
`_interlockedbittestandreset_acq`, `_interlockedbittestandreset_nf`, `_interlockedbittestandreset_rel`	ARM, ARM64	<intrin.h>
`_interlockedbittestandreset64_acq`, `_interlockedbittestandreset64_nf`, `_interlockedbittestandreset64_rel`	ARM64	<intrin.h>
`_interlockedbittestandreset_HLEAcquire`, `_interlockedbittestandreset_HLERelease`	x86, x64	<immintrin.h>
`_interlockedbittestandreset64`	x64, ARM64	<intrin.h>
`_interlockedbittestandreset64_HLEAcquire`, `_interlockedbittestandreset64_HLERelease`	x64	<immintrin.h>

Remarks

On x86 and x64 processors, these intrinsics use the lock btr instruction, that reads and sets the specified bit to zero in an atomic operation.

On ARM processors, use the intrinsics with _acq and _rel suffixes for acquire and release semantics, such as at the beginning and end of a critical section. The ARM intrinsics with an _nf ("no fence") suffix don't act as a memory barrier.

On Intel processors that support Hardware Lock Elision (HLE) instructions, the intrinsics with _HLEAcquire and _HLERelease suffixes include a hint to the processor that can accelerate performance by eliminating a lock write step in hardware. If these intrinsics are called on processors that don't support HLE, the hint is ignored.

These routines are only available as intrinsics.

END Microsoft Specific