x86-64.net

Instruction

VFPCLASSSS

Tests the low single for the classes an immediate selects, such as NaN, zero or infinity, and writes the result to a mask register.

Extensions
Forms
2 (2 EVEX)
Data
Intel XED v2026.08.23

Forms

Every encoding of VFPCLASSSS that Intel XED knows, one row per XED instruction form (iform). How to read the notation.
InstructionEncodingRequires
VFPCLASSSS k {k}, xmm, imm8 VFPCLASSSS_MASKmskw_MASKmskw_XMMf32_IMM8_AVX512EVEX.LIG.66.0F3A.W0 67 /r ibAVX10.1 or AVX512DQ
VFPCLASSSS k {k}, m32, imm8 VFPCLASSSS_MASKmskw_MASKmskw_MEMf32_IMM8_AVX512EVEX.LIG.66.0F3A.W0 67 /r ibAVX10.1 or AVX512DQ

Intrinsics

The C intrinsics of Clang 23.1.2 that compile to VFPCLASSSS, each with the form it compiles to and the Clang options it needs. The forms come from compiling every intrinsic and decoding the result with Intel XED; all intrinsics A–Z explains the method.

IntrinsicCompiles to
_mm_fpclass_ss_mask __mmask8 _mm_fpclass_ss_mask(__m128 A, const int imm)

VFPCLASSSS k, xmm, imm8 EVEX.LIG -mavx512dq

_mm_mask_fpclass_ss_mask __mmask8 _mm_mask_fpclass_ss_mask(__mmask8 U, __m128 A, const int imm)

VFPCLASSSS k {k}, xmm, imm8 EVEX.LIG -mavx512dq

CPUID and processors

Each form belongs to an XED ISA set. A form can be used when the processor reports every CPUID bit of one of its ISA set's alternatives.

CPUID requirements and processors of the XED ISA sets above. Alternatives are separated by “or”; processors follow XED’s chip model, which covers AMD processors up to Zen 2.
ISA setCPUIDProcessors in XED
AVX512DQ_SCALAR

AVX10.1
CPUID.(EAX=07H,ECX=1):EDX[19] AVX10
CPUID.(EAX=24H,ECX=0):EBX[7:0] ≥ 1 AVX10 version

or

AVX512DQ
CPUID.(EAX=07H,ECX=0):EBX[17] AVX512DQ

Cannon Lake, Ice Lake (client), Tiger Lake, Nova Lake, Skylake-SP, Cascade Lake, Cooper Lake, Ice Lake (server), Sapphire Rapids, Emerald Rapids, Granite Rapids, Diamond Rapids

More AVX10.1 instructions

All 686 AVX10.1 instructions

Sources

  1. Intel XED v2026.08.23 (commit 0bcb6237345c): forms, encodings, ISA sets, CPUID bits and chip model.
  2. Clang's x86 intrinsic headers, LLVM 23.1.2 (commit 85ac56026243): the intrinsics, their signatures and doc comments, and the Clang of that release, which compiled each of them.
  3. Intel Advanced Vector Extensions 10.2 Architecture Specification, revision 6.0 (361050-006, January 2026)

The tables are derived from Intel XED, Copyright Intel Corporation, licensed under the Apache License 2.0; x86-64.net converted and reformatted them. The intrinsics and their signatures come from Clang, part of the LLVM Project, licensed under the Apache License 2.0 with LLVM Exceptions. The text is our own.