;

; jsimdcpu.asm - SIMD instruction support check

;

; Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB</ossman@cendio.se>

; Copyright (C) 2016, D. R. Commander.

;

; Based on

; x86 SIMD extension for IJG JPEG library

; Copyright (C) 1999-2006, MIYASAKA Masaru.

; For conditions of distribution and use, see copyright notice in jsimdext.inc

;

; This file should be assembled with NASM (Netwide Assembler),

; can *not* be assembled with Microsoft's MASM or any compatible

; assembler (including Borland's Turbo Assembler).

; NASM is available from http://nasm.sourceforge.net/ or

; http://sourceforge.net/project/showfiles.php?group_id=6208

%include "jsimdext.inc"

; --------------------------------------------------------------------------

    SECTION     SEG_TEXT

    BITS        64

;

; Check if the CPU supports SIMD instructions

;

; GLOBAL(unsigned int)

; jpeg_simd_cpu_support(void)

;

    align       32

    GLOBAL_FUNCTION(jpeg_simd_cpu_support)

EXTN(jpeg_simd_cpu_support):

    push        rbx

    push        rdi

    xor         rdi, rdi                ; simd support flag

    ; Assume that all x86-64 processors support SSE & SSE2 instructions

    or          rdi, JSIMD_SSE2

    or          rdi, JSIMD_SSE

    ; Check whether CPUID leaf 07H is supported

    ; (leaf 07H is used to check for AVX2 instruction support)

    mov         rax, 0

    cpuid

    cmp         rax, 7

    jl          short .return           ; Maximum leaf < 07H

    ; Check for AVX2 instruction support

    mov         rax, 7

    xor         rcx, rcx

    cpuid

    mov         rax, rbx                ; rax = Extended feature flags

    test        rax, 1<<5               ; bit5:AVX2

    jz          short .return

    ; Check for AVX2 O/S support

    mov         rax, 1

    xor         rcx, rcx

    cpuid

    test        rcx, 1<<27

    jz          short .return           ; O/S does not support XSAVE

    test        rcx, 1<<28

    jz          short .return           ; CPU does not support AVX2

    xor         rcx, rcx

    xgetbv

    and         rax, 6

    cmp         rax, 6                  ; O/S does not manage XMM/YMM state

                                        ; using XSAVE

    jnz         short .return

    or          rdi, JSIMD_AVX2

.return:

    mov         rax, rdi

    pop         rdi

    pop         rbx

    ret

; For some reason, the OS X linker does not honor the request to align the

; segment unless we do this.

    align       32