simd_instruction_set

constexpr auto spy::simd_instruction_set = detail::simd_info<>{}

inlineconstexpr

SIMD extensions set reporting value.

SIMD Instructions Sets

SIMD extensions set detection is made so that one can ask if the current SIMD extension is exactly, below or above a given reference instruction set. Detectable instructions sets depends on SIMD hardware vendor

Architecture	Supported SIMD instructions sets
X86 SSE	spy::sse1_, spy::sse2_, spy::sse3_, spy::ssse3_, spy::sse41_, spy::sse42_
X86 AVX	spy::avx_, spy::avx2_, spy::avx512_
Power PC VMX	spy::vmx_, spy::vmx_2_03_, spy::vmx_2_05_, spy::vmx_2_06_, spy::vmx_2_07_, spy::vmx_3_00_, spy::vmx_3_01_
Power PC VSX	spy::vsx_, spy::vsx_2_06_, spy::vsx_2_07_, spy::vsx_3_00_, spy::vsx_3_01_
ARM NEON	spy::neon_, spy::asimd_
ARM SVE	spy::sve_,spy::sve128_, spy::sve256_, spy::sve512_, spy::sve1024_
WASM	spy::simd128_
RISC-V	spy::rvv_`

Complete set of comparison operators is provided for those sets. Order of instructions sets are built so that if an instructions set supersedes another, it is considered greater than. For example, spy::avx_ is greater than spy::sse41_ as the former is a super-set of the later. Comparing SIMD descriptors across architecture is undefined behavior.

Moreover, the spy::simd_instruction_set object exposes a constexpr width static field that contains the size in bits of the current SIMD instructions set registers.

Example - SIMD Instructions Sets

#include <spy/spy.hpp>
#include <iostream>
 
int main()
{
  std::cout << spy::simd_instruction_set << "\n";
 
  if constexpr( spy::simd_instruction_set == spy::avx_ )
  {
    std::cout << "This code has been compiled with AVX instructions set.\n";
  }
 
  if constexpr( spy::simd_instruction_set >= spy::sse41_ )
  {
    std::cout << "This code has been compiled with at least support for SSE 4.1\n";
  }
 
  if constexpr( spy::simd_instruction_set <= spy::sse2_ )
  {
    std::cout << "This code has been compiled with support for SSE2 at most.\n";
  }
 
  std::cout << "This code can use " << spy::simd_instruction_set.width << " bits register.\n";
}

SIMD Architectures

One can also simply asks if a given family of instructions set is available.

Architecture	Generic indicator
X86	spy::x86_simd_
Power PC	spy::ppc_simd_
ARM	spy::arm_simd_
WASM	spy::wasm_simd_
RISC-V	spy::riscv_simd_

Example - SIMD Architectures

#include <spy/spy.hpp>
#include <iostream>
 
int main()
{
  if constexpr( spy::simd_instruction_set == spy::x86_simd_ )
  {
    std::cout << "This code has been compiled with some Intel SIMD instructions set.\n";
  }
 
  if constexpr( spy::simd_instruction_set == spy::arm_simd_ )
  {
    std::cout << "This code has been compiled with some ARM SIMD instructions set.\n";
  }
 
  if constexpr( spy::simd_instruction_set == spy::ppc_simd_ )
  {
    std::cout << "This code has been compiled with some Power PC SIMD instructions set.\n";
  }
 
  if constexpr( spy::simd_instruction_set == spy::wasm_simd_ )
  {
    std::cout << "This code has been compiled with WASM enabled.\n";
  }
}

Supplemental Instructions sets

Some SIMD instructions set provides supplemental instructions on top of existing system. Those supplemental instruction set can be checked using the spy::supports namespace.

Architecture	Supported SIMD instructions sets
X86 AVX	xop_, fma_, fma4_
X86 AVX512	bw_, cd_, dq_, er_, ifma_, pf_, vl_, popcntdq_
	_4fmaps_, vnniw_, vbmi_, bf16_,bitalg_, vbmi2_, vnni_, vpintersect_

Example - SIMD Architectures

#include <spy/spy.hpp>
#include <iostream>
 
int main()
{
  if      constexpr( spy::supports::fma_        ) std::cout << "This code has been compiled with FMA3 support.\n";
  else if constexpr( spy::supports::fma4_       ) std::cout << "This code has been compiled with FMA4 support.\n";
  else if constexpr( spy::supports::xop_        ) std::cout << "This code has been compiled with XOP support.\n";
  else if constexpr( spy::supports::avx512::cd_ ) std::cout << "This code has been compiled with AV512-CD support.\n";
}