fp_mode.c

//===----- lib/aarch64/fp_mode.c - Floaing-point mode utilities ---*- C -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include <stdint.h>

#include "../fp_mode.h"

#define AARCH64_TONEAREST  0x0
#define AARCH64_UPWARD     0x1
#define AARCH64_DOWNWARD   0x2
#define AARCH64_TOWARDZERO 0x3
#define AARCH64_RMODE_MASK (AARCH64_TONEAREST | AARCH64_UPWARD | \
                            AARCH64_DOWNWARD | AARCH64_TOWARDZERO)
#define AARCH64_RMODE_SHIFT 22

#define AARCH64_INEXACT     0x10

#ifndef __ARM_FP
// For soft float targets, allow changing rounding mode by overriding the weak
// __aarch64_fe_default_rmode symbol.
CRT_FE_ROUND_MODE __attribute__((weak)) __aarch64_fe_default_rmode =
    CRT_FE_TONEAREST;
#endif

CRT_FE_ROUND_MODE __fe_getround(void) {
#ifdef __ARM_FP
  uint64_t fpcr;
  __asm__ __volatile__("mrs  %0, fpcr" : "=r" (fpcr));
  fpcr = fpcr >> AARCH64_RMODE_SHIFT & AARCH64_RMODE_MASK;
  switch (fpcr) {
    case AARCH64_UPWARD:
      return CRT_FE_UPWARD;
    case AARCH64_DOWNWARD:
      return CRT_FE_DOWNWARD;
    case AARCH64_TOWARDZERO:
      return CRT_FE_TOWARDZERO;
    case AARCH64_TONEAREST:
    default:
      return CRT_FE_TONEAREST;
  }
#else
  return __aarch64_fe_default_rmode;
#endif
}

int __fe_raise_inexact(void) {
#ifdef __ARM_FP
  uint64_t fpsr;
  __asm__ __volatile__("mrs  %0, fpsr" : "=r" (fpsr));
  __asm__ __volatile__("msr  fpsr, %0" : : "ri" (fpsr | AARCH64_INEXACT));
  return 0;
#else
  return 0;
#endif
}