Add CPUID submodule

This is a small internal module which defines the API to query the Instruction
Set Architecture (ISA) of the current CPU.  This can be used for example to
select an artifact in a JLL package which is compatible with the current CPU.

base/binaryplatforms.jl

@@ -7,6 +7,62 @@ export AbstractPlatform, Platform, HostPlatform, platform_dlext, tags, arch, os,
        select_platform, platforms_match, platform_name
 import .Libc.Libdl
 
+### Submodule with information about CPU features
+module CPUID
+
+export cpu_isa
+
+"""
+    ISA(features::Set{UInt32})
+
+A structure which represents the Instruction Set Architecture (ISA) of a
+computer.  It holds the `Set` of features of the CPU.
+
+The numerical values of the features are automatically generated from the C
+source code of Julia and stored in the `features_h.jl` Julia file.
+"""
+struct ISA
+    features::Set{UInt32}
+end
+
+Base.:<=(a::ISA, b::ISA) = a.features <= b.features
+Base.:<(a::ISA,  b::ISA) = a.features <  b.features
+Base.isless(a::ISA,  b::ISA) = a < b
+
+include("features_h.jl")
+
+# Sets of features for the x86-64 microarchitectures come from
+# https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html.  Keep in sync with
+# `arch_march_isa_mapping`.
+const ISAs_by_family = Dict(
+    "x86_64" => (
+        "x86_64" => ISA(Set{UInt32}()),
+        "core2" => ISA(Set((JL_X86_sse3, JL_X86_ssse3))),
+        "nehalem" => ISA(Set((JL_X86_sse3, JL_X86_ssse3, JL_X86_sse41, JL_X86_sse42, JL_X86_popcnt))),
+        "sandybridge" => ISA(Set((JL_X86_sse3, JL_X86_ssse3, JL_X86_sse41, JL_X86_sse42, JL_X86_popcnt, JL_X86_avx, JL_X86_aes, JL_X86_pclmul))),
+        "haswell" => ISA(Set((JL_X86_movbe, JL_X86_sse3, JL_X86_ssse3, JL_X86_sse41, JL_X86_sse42, JL_X86_popcnt, JL_X86_avx, JL_X86_avx2, JL_X86_aes, JL_X86_pclmul, JL_X86_fsgsbase, JL_X86_rdrnd, JL_X86_fma, JL_X86_bmi, JL_X86_bmi2, JL_X86_f16c))),
+        "skylake" => ISA(Set((JL_X86_movbe, JL_X86_sse3, JL_X86_ssse3, JL_X86_sse41, JL_X86_sse42, JL_X86_popcnt, JL_X86_avx, JL_X86_avx2, JL_X86_aes, JL_X86_pclmul, JL_X86_fsgsbase, JL_X86_rdrnd, JL_X86_fma, JL_X86_bmi, JL_X86_bmi2, JL_X86_f16c, JL_X86_rdseed, JL_X86_adx, JL_X86_prfchw, JL_X86_clflushopt, JL_X86_xsavec, JL_X86_xsaves))),
+        "skylake_avx512" => ISA(Set((JL_X86_movbe, JL_X86_sse3, JL_X86_ssse3, JL_X86_sse41, JL_X86_sse42, JL_X86_popcnt, JL_X86_pku, JL_X86_avx, JL_X86_avx2, JL_X86_aes, JL_X86_pclmul, JL_X86_fsgsbase, JL_X86_rdrnd, JL_X86_fma, JL_X86_bmi, JL_X86_bmi2, JL_X86_f16c, JL_X86_rdseed, JL_X86_adx, JL_X86_prfchw, JL_X86_clflushopt, JL_X86_xsavec, JL_X86_xsaves, JL_X86_avx512f, JL_X86_clwb, JL_X86_avx512vl, JL_X86_avx512bw, JL_X86_avx512dq, JL_X86_avx512cd))),
+    )
+)
+
+test_cpu_feature(feature::UInt32) = ccall(:jl_test_cpu_feature, Bool, (UInt32,), feature)
+cpu_family() = String(Sys.ARCH)
+
+"""
+    cpu_isa()
+
+Return the [`ISA`](@ref) (instruction set architecture) of the current CPU.
+"""
+function cpu_isa()
+    all_features = last(last(get(ISAs_by_family, cpu_family(), "" => [ISA(Set{UInt32}())]))).features
+    return ISA(Set{UInt32}(feat for feat in all_features if test_cpu_feature(feat)))
+end
+
+end # module CPUID
+
+using .CPUID
+
 # This exists to ease compatibility with old-style Platform objects
 abstract type AbstractPlatform; end
 
@@ -563,6 +619,15 @@ const arch_mapping = Dict(
     "armv6l" => "armv6l",
     "powerpc64le" => "p(ower)?pc64le",
 )
+# Keep this in sync with `CPUID.ISAs_by_family`
+const arch_march_isa_mapping = Dict(
+    "x86_64" => Dict(
+        "x86_64" => CPUID.ISAs_by_family["x86_64"][1].second, # x86_64
+        "avx" => CPUID.ISAs_by_family["x86_64"][4], # sandybridge
+        "avx2" => CPUID.ISAs_by_family["x86_64"][5], # haswell
+        "avx512" => CPUID.ISAs_by_family["x86_64"][7], # skylake_avx512
+    )
+)
 const os_mapping = Dict(
     "macos" => "-apple-darwin[\\d\\.]*",
     "freebsd" => "-(.*-)?freebsd[\\d\\.]*",

test/binaryplatforms.jl

@@ -1,4 +1,16 @@
-using Test, Base.BinaryPlatforms
+using Test, Base.BinaryPlatforms, Base.BinaryPlatforms.CPUID
+
+@testset "CPUID" begin
+    @test CPUID.cpu_isa() isa CPUID.ISA
+
+    get_x86_64(n) = (CPUID.ISAs_by_family["x86_64"][n].second)
+    @test get_x86_64(2) <  get_x86_64(4)
+    @test get_x86_64(5) <= get_x86_64(5)
+    @test get_x86_64(3) >= get_x86_64(3)
+    @test get_x86_64(7) >= get_x86_64(1)
+    @test sort([get_x86_64(6), get_x86_64(4), get_x86_64(2), get_x86_64(4)]) ==
+        [get_x86_64(2), get_x86_64(4), get_x86_64(4), get_x86_64(6)]
+end
 
 # Helper constructor to create a Platform with `validate_strict` set to `true`.
 P(args...; kwargs...) = Platform(args...; validate_strict=true, kwargs...)
@@ -354,4 +366,4 @@ end
     @test !platforms_match(ac, bc)
     @test platforms_match(ac, ac)
     @test platforms_match(bc, bc)
-end
+end