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76 lines
2.5 KiB
C
76 lines
2.5 KiB
C
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/* Software floating-point emulation.
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Truncate bfloat16 into IEEE half.
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Copyright (C) 2022-2024 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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In addition to the permissions in the GNU Lesser General Public
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License, the Free Software Foundation gives you unlimited
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permission to link the compiled version of this file into
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combinations with other programs, and to distribute those
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combinations without any restriction coming from the use of this
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file. (The Lesser General Public License restrictions do apply in
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other respects; for example, they cover modification of the file,
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and distribution when not linked into a combine executable.)
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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 "soft-fp.h"
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#include "half.h"
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#include "brain.h"
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#include "single.h"
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/* BFtype and HFtype are unordered, neither is a superset or subset
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of each other. Convert BFtype to SFtype (lossless) and then
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truncate to HFtype. */
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HFtype
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__truncbfhf2 (BFtype a)
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{
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FP_DECL_EX;
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FP_DECL_H (A);
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FP_DECL_S (B);
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FP_DECL_B (R);
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SFtype b;
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HFtype r;
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FP_INIT_ROUNDMODE;
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/* Optimize BFtype to SFtype conversion to simple left shift
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by 16 if possible, we don't need to raise exceptions on sNaN
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here as the SFtype to HFtype truncation should do that too. */
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if (sizeof (BFtype) == 2
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&& sizeof (unsigned short) == 2
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&& sizeof (SFtype) == 4
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&& sizeof (unsigned int) == 4)
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{
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union { BFtype a; unsigned short b; } u1;
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union { SFtype a; unsigned int b; } u2;
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u1.a = a;
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u2.b = (u1.b << 8) << 8;
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b = u2.a;
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}
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else
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{
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FP_UNPACK_RAW_B (A, a);
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FP_EXTEND (S, B, 1, 1, B, A);
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FP_PACK_RAW_S (b, B);
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}
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FP_UNPACK_SEMIRAW_S (B, b);
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FP_TRUNC (H, S, 1, 1, R, B);
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FP_PACK_SEMIRAW_H (r, R);
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FP_HANDLE_EXCEPTIONS;
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return r;
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}
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