diff options
Diffstat (limited to 'UefiCpuPkg/Library/BaseUefiCpuLib/X64/InitializeFpu.asm')
-rw-r--r-- | UefiCpuPkg/Library/BaseUefiCpuLib/X64/InitializeFpu.asm | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/UefiCpuPkg/Library/BaseUefiCpuLib/X64/InitializeFpu.asm b/UefiCpuPkg/Library/BaseUefiCpuLib/X64/InitializeFpu.asm new file mode 100644 index 0000000000..34c6de6f53 --- /dev/null +++ b/UefiCpuPkg/Library/BaseUefiCpuLib/X64/InitializeFpu.asm @@ -0,0 +1,59 @@ +;------------------------------------------------------------------------------
+;*
+;* Copyright 2009, Intel Corporation
+;* All rights reserved. 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.
+;*
+;*
+;------------------------------------------------------------------------------
+
+
+.const
+;
+; Float control word initial value:
+; all exceptions masked, double-precision, round-to-nearest
+;
+mFpuControlWord DW 027Fh
+;
+; Multimedia-extensions control word:
+; all exceptions masked, round-to-nearest, flush to zero for masked underflow
+;
+mMmxControlWord DD 01F80h
+
+.code
+
+
+; +; 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). +;
+InitializeFloatingPointUnits PROC PUBLIC
+
+ ;
+ ; Initialize floating point units
+ ;
+ finit
+ fldcw mFpuControlWord
+
+ ;
+ ; Set OSFXSR bit 9 in CR4
+ ;
+ mov rax, cr4
+ or rax, BIT9
+ mov cr4, rax
+
+ ldmxcsr mMmxControlWord
+
+ ret
+InitializeFloatingPointUnits ENDP
+
+END
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