feature detection inlining

gistfile1.txt

// test_dynamic.rs
#![crate_type="lib"]

#[cfg(target_arch = "x86")]
use std::arch::x86::*;
#[cfg(target_arch = "x86_64")]
use std::arch::x86_64::*;

pub fn add_scalar(a: &[f32], b: &[f32], c: &mut [f32]) {
    for ((a, b), c) in a.iter().zip(b.iter()).zip(c.iter_mut()) {
        *c = a + b;
    }
}

#[cfg_attr(any(target_arch = "x86", target_arch = "x86_64"), target_feature(enable = "sse2"))]
pub unsafe fn add_sse2(a: &[f32], b: &[f32], c: &mut [f32]) {
    // for simplicity assume length is a multiple of chunk size
    for ((a, b), c) in a.chunks(4).zip(b.chunks(4)).zip(c.chunks_mut(4)) {
        _mm_storeu_ps(
            c.as_mut_ptr(),
            _mm_add_ps(
                _mm_loadu_ps(a.as_ptr()),
                _mm_loadu_ps(b.as_ptr())));
    }
}

#[cfg_attr(any(target_arch = "x86", target_arch = "x86_64"), target_feature(enable = "avx2"))]
pub unsafe fn add_avx2(a: &[f32], b: &[f32], c: &mut [f32]) {
    // for simplicity assume length is a multiple of chunk size
    for ((a, b), c) in a.chunks(8).zip(b.chunks(8)).zip(c.chunks_mut(8)) {
        _mm256_storeu_ps(
            c.as_mut_ptr(),
            _mm256_add_ps(
                _mm256_loadu_ps(a.as_ptr()),
                _mm256_loadu_ps(b.as_ptr())));
    }
}

pub fn add(a: &[f32], b: &[f32], c: &mut [f32]) {
    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    {
        // const TEST: u32 = _MM_SHUFFLE(3, 3, 0, 0);
        if is_x86_feature_detected!("avx2") {
            return unsafe { add_avx2(a, b, c) };
        }
        if is_x86_feature_detected!("sse2") {
            return unsafe { add_sse2(a, b, c) };
        }
    }
    add_scalar(a, b, c);
}


// compiled with rust 1.27 
// rustc -g -O -C lto=fat test_dynamic.rs
// objdump -dr libtest_dynamic.rlib | rustfilt

0000000000000000 <test_dynamic::add>:
   0:	55                   	push   %rbp
   1:	41 57                	push   %r15
   3:	41 56                	push   %r14
   5:	41 55                	push   %r13
   7:	41 54                	push   %r12
   9:	53                   	push   %rbx
   a:	50                   	push   %rax
   b:	4d 89 ce             	mov    %r9,%r14
   e:	4d 89 c7             	mov    %r8,%r15
  11:	49 89 cc             	mov    %rcx,%r12
  14:	49 89 d5             	mov    %rdx,%r13
  17:	48 89 f3             	mov    %rsi,%rbx
  1a:	48 89 fd             	mov    %rdi,%rbp
  1d:	bf 0f 00 00 00       	mov    $0xf,%edi
  22:	e8 00 00 00 00       	callq  27 <test_dynamic::add+0x27>
			23: R_X86_64_PLT32	std::stdsimd::arch::detect::os::check_for-0x4
  27:	48 89 ef             	mov    %rbp,%rdi
  2a:	48 89 de             	mov    %rbx,%rsi
  2d:	4c 89 ea             	mov    %r13,%rdx
  30:	4c 89 e1             	mov    %r12,%rcx
  33:	4d 89 f8             	mov    %r15,%r8
  36:	4d 89 f1             	mov    %r14,%r9
  39:	48 83 c4 08          	add    $0x8,%rsp
  3d:	84 c0                	test   %al,%al
  3f:	74 0f                	je     50 <test_dynamic::add+0x50>
  41:	5b                   	pop    %rbx
  42:	41 5c                	pop    %r12
  44:	41 5d                	pop    %r13
  46:	41 5e                	pop    %r14
  48:	41 5f                	pop    %r15
  4a:	5d                   	pop    %rbp
  4b:	e9 00 00 00 00       	jmpq   50 <test_dynamic::add+0x50>
			4c: R_X86_64_PLT32	test_dynamic::add_avx2-0x4
  50:	5b                   	pop    %rbx
  51:	41 5c                	pop    %r12
  53:	41 5d                	pop    %r13
  55:	41 5e                	pop    %r14
  57:	41 5f                	pop    %r15
  59:	5d                   	pop    %rbp
  5a:	e9 00 00 00 00       	jmpq   5f <test_dynamic::add+0x5f>
			5b: R_X86_64_PLT32	test_dynamic::add_sse2-0x4

// compiled with rust nightly + latest stdsimd
// rustc -g -O -C lto=fat test_dynamic.rs
// objdump -dr libtest_dynamic.rlib | rustfilt

0000000000000000 <test_dynamic::add>:
   0:	55                   	push   %rbp
   1:	41 57                	push   %r15
   3:	41 56                	push   %r14
   5:	41 55                	push   %r13
   7:	41 54                	push   %r12
   9:	53                   	push   %rbx
   a:	50                   	push   %rax
   b:	4d 89 c7             	mov    %r8,%r15
   e:	49 89 cc             	mov    %rcx,%r12
  11:	49 89 d5             	mov    %rdx,%r13
  14:	48 89 f3             	mov    %rsi,%rbx
  17:	48 89 fd             	mov    %rdi,%rbp
  1a:	4c 8b 35 00 00 00 00 	mov    0x0(%rip),%r14        # 21 <test_dynamic::add+0x21>
			1d: R_X86_64_GOTPCREL	std::stdsimd::arch::detect::cache::CACHE-0x4
  21:	49 8b 06             	mov    (%r14),%rax
  24:	48 83 f8 ff          	cmp    $0xffffffffffffffff,%rax
  28:	75 10                	jne    3a <test_dynamic::add+0x3a>
  2a:	4c 89 0c 24          	mov    %r9,(%rsp)
  2e:	e8 00 00 00 00       	callq  33 <test_dynamic::add+0x33>
			2f: R_X86_64_PLT32	std::stdsimd::arch::detect::os::detect_features-0x4
  33:	4c 8b 0c 24          	mov    (%rsp),%r9
  37:	49 89 06             	mov    %rax,(%r14)
  3a:	49 8b 06             	mov    (%r14),%rax
  3d:	48 89 ef             	mov    %rbp,%rdi
  40:	48 89 de             	mov    %rbx,%rsi
  43:	4c 89 ea             	mov    %r13,%rdx
  46:	4c 89 e1             	mov    %r12,%rcx
  49:	4d 89 f8             	mov    %r15,%r8
  4c:	48 83 c4 08          	add    $0x8,%rsp
  50:	66 85 c0             	test   %ax,%ax
  53:	78 0f                	js     64 <test_dynamic::add+0x64>
  55:	5b                   	pop    %rbx
  56:	41 5c                	pop    %r12
  58:	41 5d                	pop    %r13
  5a:	41 5e                	pop    %r14
  5c:	41 5f                	pop    %r15
  5e:	5d                   	pop    %rbp
  5f:	e9 00 00 00 00       	jmpq   64 <test_dynamic::add+0x64>
			60: R_X86_64_PLT32	test_dynamic::add_sse2-0x4
  64:	5b                   	pop    %rbx
  65:	41 5c                	pop    %r12
  67:	41 5d                	pop    %r13
  69:	41 5e                	pop    %r14
  6b:	41 5f                	pop    %r15
  6d:	5d                   	pop    %rbp
  6e:	e9 00 00 00 00       	jmpq   73 <test_dynamic::add+0x73>
			6f: R_X86_64_PLT32	test_dynamic::add_avx2-0x4