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;------------------------------------------------------------------------------
;*
;* Copyright (c) 2009 - 2017, Intel Corporation. All rights reserved.<BR>
;* This program and the accompanying materials
;* are licensed and made available under the terms and conditions of the BSD License
;* which accompanies this distribution. The full text of the license may be found at
;* http://opensource.org/licenses/bsd-license.php
;*
;* THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
;* WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
;*
;*
;------------------------------------------------------------------------------
SECTION .rodata
;
; Float control word initial value:
; all exceptions masked, double-extended-precision, round-to-nearest
;
mFpuControlWord: DW 0x37F
;
; Multimedia-extensions control word:
; all exceptions masked, round-to-nearest, flush to zero for masked underflow
;
mMmxControlWord: DD 0x1F80
DEFAULT REL
SECTION .text
;
; Initializes floating point units for requirement of UEFI specification.
;
; This function initializes floating-point control word to 0x027F (all exceptions
; masked,double-precision, round-to-nearest) and multimedia-extensions control word
; (if supported) to 0x1F80 (all exceptions masked, round-to-nearest, flush to zero
; for masked underflow).
;
global ASM_PFX(InitializeFloatingPointUnits)
ASM_PFX(InitializeFloatingPointUnits):
;
; Initialize floating point units
;
; The following opcodes stand for instruction 'finit'
; to be supported by some 64-bit assemblers
;
DB 0x9B, 0xDB, 0xE3
fldcw [mFpuControlWord]
;
; Set OSFXSR bit 9 in CR4
;
mov rax, cr4
or rax, BIT9
mov cr4, rax
ldmxcsr [mMmxControlWord]
ret
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