audk/StdLib/LibC/Main/X64/fpu_rmode.asm

42 lines
1.7 KiB
NASM

;------------------------------------------------------------------------------
; Return the current FPU rounding mode.
;
; MASM implementation of the flt_rounds function from NetBSD.
;
; Copyright (c) 2010, Intel Corporation. All rights reserved.<BR>
; 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.
;
;------------------------------------------------------------------------------
.code
;_map BYTE 1 ; round to nearest
; BYTE 3 ; round to negative infinity
; BYTE 2 ; round to positive infinity
; BYTE 0 ; round to zero
;------------------------------------------------------------------------------
; int
; EFIAPI
; fpu_rmode( void );
;
; VC++ always creates space for 4 parameters on the stack, whether they are
; used or not. We use one for temporary storage since the only variant of
; fnstcw saves to memory, NOT a register.
;------------------------------------------------------------------------------
internal_FPU_rmode PROC
fnstcw [rsp + 8] ; save 16-bit FPU Control Word
mov eax, [rsp + 8] ; get the saved FPU Control Word
shr eax, 10
and rax, 3 ; index is only the LSB two bits in RAX
ret ; Return rounding mode in RAX
internal_FPU_rmode ENDP
END