All instructionsArm64 · AArch64Logical

BSL

Select bits using a mask

Choose each bit from the first data input where the mask is one, and from the second where it is zero.

AdvSIMD8-bit bits elements

Instruction forms

1 in this sample
FormBitsRequiresEncoding
BSL Vd.16B,Vn.16B,Vm.16B128AdvSIMD—
128 bits · 16 × 8-bit elements

Explore the operation

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Operation

Pseudo-C · selected form
dst = (mask AND a) OR ((NOT mask) AND b)

Simplified pseudocode for the selected form.

What to watch for

  • Selection happens per bit, not per byte.
  • The assembly destination initially holds the mask.

Corresponding intrinsics

C / C++ · selected form
vbslq_u8
uint8x16_t vbslq_u8( uint8x16_t a, uint8x16_t b, uint8x16_t c)
#include <arm_neon.h>AdvSIMD

AArch64 mapping documented by ACLE; compiler output depends on optimization and context.

Documented mapping

BSL Vd.16B,Vn.16B,Vm.16B

Architectural details

Flags
NZCV unchanged.
Destination
Writes all 128 bits of the selected V destination register.
Encoding
Encoding details have not been imported for this form.
Operands
a -> Vd.16B b -> Vn.16B c -> Vm.16B
  • Vdwrite · 128 bits (16 × 8)
  • aread · 128 bits (16 × 8) · unsigned
  • bread · 128 bits (16 × 8) · unsigned
  • cread · 128 bits (16 × 8) · unsigned
Coverage
Selected 128-bit AArch64 AdvSIMD (Neon) forms from ACLE. Scalar, other element arrangements, SVE, and SME forms are outside this sample.
Exception information & execution requirements

    Complete exception conditions have not been imported.

    Availability depends on execution-level controls for AdvSIMD. This ACLE import does not contain an exhaustive architectural exception list.

    Feature availability alone does not guarantee execution: OS state and execution-level controls also apply. Use the linked architecture documentation for the full exception conditions.

    Performance measurements are not included in this preview. Latency and throughput depend on the exact form and microarchitecture.

    Sources & provenance

    Technical fields are imported from pinned upstream files. Explanations and explorer behavior are maintained separately.

    Arm · advsimd.md
    Revision
    3a8fb2b1145b27ba0a9110ed32f3a6cfdad6c002
    SHA-256
    722dcf758d7a6dbbab54210d55bbce73a6db7691bb4092112375bf096563fd73
    Terms
    CC-BY-SA-4.0 AND Apache-Patent-License
    View pinned upstream file ↗

    Intel sources are a documentation preview. Arm ACLE mappings are adapted under CC BY-SA 4.0 with an additional patent license. Arm MRS encoding data is distributed under BSD-3-Clause. © Arm Limited and contributors. Coverage and attribution.