1;------------------------------------------------------------------------------
2;
3; Copyright (c) 2014, Intel Corporation. All rights reserved.<BR>
4; This program and the accompanying materials
5; are licensed and made available under the terms and conditions of the BSD License
6; which accompanies this distribution.  The full text of the license may be found at
7; http://opensource.org/licenses/bsd-license.php.
8;
9; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
10; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
11;
12; Abstract:
13;
14;------------------------------------------------------------------------------
15
16    .686
17    .model  flat,C
18    .const
19;
20; Float control word initial value:
21; all exceptions masked, double-precision, round-to-nearest
22;
23mFpuControlWord       DW      027Fh
24;
25; Multimedia-extensions control word:
26; all exceptions masked, round-to-nearest, flush to zero for masked underflow
27;
28mMmxControlWord       DD      01F80h
29
30    .xmm
31    .code
32
33;
34; Initializes floating point units for requirement of UEFI specification.
35;
36; This function initializes floating-point control word to 0x027F (all exceptions
37; masked,double-precision, round-to-nearest) and multimedia-extensions control word
38; (if supported) to 0x1F80 (all exceptions masked, round-to-nearest, flush to zero
39; for masked underflow).
40;
41InitializeFloatingPointUnits PROC PUBLIC
42
43    push    ebx
44
45    ;
46    ; Initialize floating point units
47    ;
48    finit
49    fldcw   mFpuControlWord
50
51    ;
52    ; Use CpuId instructuion (CPUID.01H:EDX.SSE[bit 25] = 1) to test
53    ; whether the processor supports SSE instruction.
54    ;
55    mov     eax, 1
56    cpuid
57    bt      edx, 25
58    jnc     Done
59
60    ;
61    ; Set OSFXSR bit 9 in CR4
62    ;
63    mov     eax, cr4
64    or      eax, BIT9
65    mov     cr4, eax
66
67    ;
68    ; The processor should support SSE instruction and we can use
69    ; ldmxcsr instruction
70    ;
71    ldmxcsr mMmxControlWord
72Done:
73    pop     ebx
74
75    ret
76
77InitializeFloatingPointUnits ENDP
78
79END
80