v_mbcnt_lo_u32_b32 GPU Native ISA AMD Vector

V MBCNT LO U32 B32 Vector Arithmetic

v_mbcnt_lo_u32_b32

For each lane 0 <= N < 32, examine the N least significant bits of the first input and count how many of those bits are "1".

Encoding

Verified bit-level encoding data is not yet available for this instruction. The instruction-format classification below (VOP2) is well-documented and stable; exact per-target opcode/field bit positions have not yet been imported from a verified source.
Format VOP2
Execution Unit

Operands

Operand details have not yet been curated for this instruction.

GFX Target Compatibility

TargetSupport
gfx1100✅ Supported

Related

More in Vector Arithmetic

Reference

AMDGPU / GFX ISA

Description

For each lane 0 <= N < 32, examine the N least significant bits of the first input and count how many of those bits are "1". For each lane 32 <= N < 64, all "1" bits in the first input are counted. Add this count to the value in the second input and store the result into a vector register.

Example

v_mbcnt_lo_u32_b32 v5, v1, v2

A real instruction accepted by the LLVM assembler, taken verbatim from LLVM's own AMDGPU MC test suite (gfx11). Not from an AMD document, and not authored here.

Sources