1 //===----- lib/i386/fp_mode.c - Floaing-point mode utilities -----*- C -*-====//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "../fp_mode.h"
10 
11 #define X87_TONEAREST  0x0000
12 #define X87_DOWNWARD   0x0400
13 #define X87_UPWARD     0x0800
14 #define X87_TOWARDZERO 0x0c00
15 #define X87_RMODE_MASK (X87_TONEAREST | X87_UPWARD | X87_DOWNWARD | X87_TOWARDZERO)
16 
17 CRT_FE_ROUND_MODE __fe_getround(void) {
18   // Assume that the rounding mode state for the fpu agrees with the SSE unit.
19   unsigned short cw;
20   __asm__ __volatile__ ("fnstcw %0" : "=m" (cw));
21 
22   switch (cw & X87_RMODE_MASK) {
23     case X87_TONEAREST:
24       return CRT_FE_TONEAREST;
25     case X87_DOWNWARD:
26       return CRT_FE_DOWNWARD;
27     case X87_UPWARD:
28       return CRT_FE_UPWARD;
29     case X87_TOWARDZERO:
30       return CRT_FE_TOWARDZERO;
31   }
32   return CRT_FE_TONEAREST;
33 }
34 
35 int __fe_raise_inexact(void) {
36   float f = 1.0f, g = 3.0f;
37   __asm__ __volatile__ ("fdivs %1" : "+t" (f) : "m" (g));
38   return 0;
39 }
40