1 files changed, 41 insertions, 0 deletions
diff --git a/StdLib/LibC/Main/X64/fpu_rmode.asm b/StdLib/LibC/Main/X64/fpu_rmode.asm
new file mode 100644
index 0000000000..36b0d11ccd
--- /dev/null
+++ b/StdLib/LibC/Main/X64/fpu_rmode.asm
@@ -0,0 +1,41 @@
+;------------------------------------------------------------------------------
+; 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