StdLib/LibC/Main/X64/fpu_rmode.asm

   1 ;------------------------------------------------------------------------------
   2 ; Return the current FPU rounding mode.
   3 ;
   4 ; MASM implementation of the flt_rounds function from NetBSD.
   5 ;
   6 ; Copyright (c) 2010, Intel Corporation. All rights reserved.<BR>
   7 ; This program and the accompanying materials
   8 ; are licensed and made available under the terms and conditions of the BSD License
   9 ; which accompanies this distribution.  The full text of the license may be found at
  10 ; http://opensource.org/licenses/bsd-license.php.
  11 ;
  12 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  13 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  14 ;
  15 ;------------------------------------------------------------------------------
  16
  17     .code
  18
  19 ;_map  BYTE  1     ; round to nearest
  20 ;      BYTE  3     ; round to negative infinity
  21 ;      BYTE  2     ; round to positive infinity
  22 ;      BYTE  0     ; round to zero
  23
  24 ;------------------------------------------------------------------------------
  25 ; int
  26 ; EFIAPI
  27 ; fpu_rmode( void );
  28 ;
  29 ; VC++ always creates space for 4 parameters on the stack, whether they are
  30 ; used or not.  We use one for temporary storage since the only variant of
  31 ; fnstcw saves to memory, NOT a register.
  32 ;------------------------------------------------------------------------------
  33 internal_FPU_rmode    PROC
  34     fnstcw    [rsp + 8]       ; save 16-bit FPU Control Word
  35     mov       eax, [rsp + 8]  ; get the saved FPU Control Word
  36     shr       eax, 10
  37     and       rax, 3          ; index is only the LSB two bits in RAX
  38     ret                       ; Return rounding mode in RAX
  39 internal_FPU_rmode    ENDP
  40
  41     END