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01e80428f7
The convert_bit macro allows the compiler to translate the bit positions more efficiently. The assumption of only running at program startup allows eliding the __ieee_get_fp_control call.
62 lines
2.4 KiB
C
62 lines
2.4 KiB
C
/* Set FP exception mask and rounding mode.
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Copyright (C) 1996-2012 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library. If not, see
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<http://www.gnu.org/licenses/>. */
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#include <fpu_control.h>
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#include <fenv_libc.h>
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#define convert_bit(M, F, T) \
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((T) < (F) \
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? ((M) / ((F) / (T))) & (T) \
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: ((M) & (F)) * ((T) / (F)))
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void
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__setfpucw (fpu_control_t fpu_control)
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{
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unsigned long fpcr, swcr, fc = (int)fpu_control;
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/* ??? If this was a real external interface we'd want to read the current
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exception state with __ieee_get_fp_control. But this is an internal
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function only called at process startup, so there's no point in trying
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to preserve exceptions that cannot have been raised yet. Indeed, this
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entire function is likely to be one big nop unless the user overrides
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the default __fpu_control variable. */
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/* Convert the rounding mode from fpu_control.h format. */
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const unsigned long conv_rnd
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= ( (FE_TOWARDZERO << (_FPU_RC_ZERO >> 8))
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| (FE_DOWNWARD << (_FPU_RC_DOWN >> 8))
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| (FE_TONEAREST << (_FPU_RC_NEAREST >> 8))
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| (FE_UPWARD << (_FPU_RC_UP >> 8)));
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fpcr = ((conv_rnd >> ((fc >> 8) & 3)) & 3) << FPCR_ROUND_SHIFT;
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/* Convert the exception mask from fpu_control.h format. */
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swcr = convert_bit (~fc, _FPU_MASK_IM, FE_INVALID >> SWCR_ENABLE_SHIFT);
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swcr |= convert_bit (~fc, _FPU_MASK_DM, FE_UNDERFLOW >> SWCR_ENABLE_SHIFT);
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swcr |= convert_bit (~fc, _FPU_MASK_ZM, FE_DIVBYZERO >> SWCR_ENABLE_SHIFT);
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swcr |= convert_bit (~fc, _FPU_MASK_OM, FE_OVERFLOW >> SWCR_ENABLE_SHIFT);
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swcr |= convert_bit (~fc, _FPU_MASK_PM, FE_INEXACT >> SWCR_ENABLE_SHIFT);
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/* Install everything. */
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__fpu_control = fc;
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asm volatile ("mt_fpcr %0" : : "f"(fpcr));
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__ieee_set_fp_control(swcr);
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}
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