UefiCpuPkg: Replace BSD License with BSD+Patent License

[mirror_edk2.git] / UefiCpuPkg / Library / BaseUefiCpuLib / Ia32 / InitializeFpu.nasm

;------------------------------------------------------------------------------\r
;*\r
;*   Copyright (c) 2016 - 2017, Intel Corporation. All rights reserved.<BR>\r
;*   SPDX-License-Identifier: BSD-2-Clause-Patent\r
;*\r
;*\r
;------------------------------------------------------------------------------\r
\r
    SECTION .rodata\r
\r
;\r
; Float control word initial value:\r
; all exceptions masked, double-precision, round-to-nearest\r
;\r
mFpuControlWord: DW 0x27F\r
;\r
; Multimedia-extensions control word:\r
; all exceptions masked, round-to-nearest, flush to zero for masked underflow\r
;\r
mMmxControlWord: DD 0x1F80\r
\r
    SECTION .text\r
\r
;\r
; Initializes floating point units for requirement of UEFI specification.\r
;\r
; This function initializes floating-point control word to 0x027F (all exceptions\r
; masked,double-precision, round-to-nearest) and multimedia-extensions control word\r
; (if supported) to 0x1F80 (all exceptions masked, round-to-nearest, flush to zero\r
; for masked underflow).\r
;\r
global ASM_PFX(InitializeFloatingPointUnits)\r
ASM_PFX(InitializeFloatingPointUnits):\r
\r
    push    ebx\r
\r
    ;\r
    ; Initialize floating point units\r
    ;\r
    finit\r
    fldcw   [mFpuControlWord]\r
\r
    ;\r
    ; Use CpuId instructuion (CPUID.01H:EDX.SSE[bit 25] = 1) to test\r
    ; whether the processor supports SSE instruction.\r
    ;\r
    mov     eax, 1\r
    cpuid\r
    bt      edx, 25\r
    jnc     Done\r
\r
    ;\r
    ; Set OSFXSR bit 9 in CR4\r
    ;\r
    mov     eax, cr4\r
    or      eax, BIT9\r
    mov     cr4, eax\r
\r
    ;\r
    ; The processor should support SSE instruction and we can use\r
    ; ldmxcsr instruction\r
    ;\r
    ldmxcsr [mMmxControlWord]\r
Done:\r
    pop     ebx\r
\r
    ret\r
\r