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
17CRT_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
35int __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

source code of compiler-rt/lib/builtins/i386/fp_mode.c