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