Removed use of pre-initialized global data in this file as it was causing problems...

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

#------------------------------------------------------------------------------\r
#*\r
#*   Copyright 2009, Intel Corporation\r
#*   All rights reserved. This program and the accompanying materials\r
#*   are licensed and made available under the terms and conditions of the BSD License\r
#*   which accompanies this distribution.  The full text of the license may be found at\r
#*   http://opensource.org/licenses/bsd-license.php\r
#*\r
#*   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
#*   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
#*\r
#*\r
#------------------------------------------------------------------------------\r
\r
\r
\r
#\r
# Float control word initial value: \r
# all exceptions masked, double-precision, round-to-nearest\r
#\r
ASM_PFX(mFpuControlWord): .word     0x027F\r
#\r
# Multimedia-extensions control word:\r
# all exceptions masked, round-to-nearest, flush to zero for masked underflow\r
#\r
ASM_PFX(mMmxControlWord): .long     0x01F80\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
ASM_GLOBAL ASM_PFX(InitializeFloatingPointUnits)\r
ASM_PFX(InitializeFloatingPointUnits):\r
\r
    pushl   %ebx\r
\r
    #\r
    # Initialize floating point units\r
    #\r
    finit\r
    fldcw   ASM_PFX(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
    movl    $1,  %eax\r
    cpuid\r
    btl     $25, %edx\r
    jnc     Done\r
    \r
    #\r
    # Set OSFXSR bit 9 in CR4\r
    #\r
    movl    %cr4, %eax \r
    or      $200, %eax\r
    movl    %eax, %cr4\r
    \r
    #\r
    # The processor should support SSE instruction and we can use\r
    # ldmxcsr instruction\r
    #\r
    ldmxcsr ASM_PFX(mMmxControlWord)\r
\r
Done:\r
    popl    %ebx\r
\r
    ret\r
\r
#END\r
\r