compiler-rt/lib/builtins/i386/fp_mode.c

   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 }