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431 lines
14 KiB
C
431 lines
14 KiB
C
/* Simulator Floating-point support.
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Copyright 1997-2018 Free Software Foundation, Inc.
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Contributed by Cygnus Support.
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This file is part of GDB, the GNU debugger.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef SIM_FPU_H
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#define SIM_FPU_H
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/* The FPU intermediate type - this object, passed by reference,
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should be treated as opaque.
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Pragmatics - pass struct by ref:
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The alternatives for this object/interface that were considered
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were: a packed 64 bit value; an unpacked structure passed by value;
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and an unpacked structure passed by reference.
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The packed 64 bit value was rejected because: it limited the
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precision of intermediate values; reasonable performance would only
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be achieved when the sim_fpu package was in-lined allowing repeated
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unpacking operations to be eliminated.
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For unpacked structures (passed by value and reference), the code
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quality of GCC-2.7 (on x86) for each alternative was compared.
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Needless to say the results, while better than for a packed 64 bit
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object, were still poor (GCC had only limited support for the
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optimization of references to structure members). Regardless, the
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struct-by-ref alternative achieved better results when compiled
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with (better speed) and without (better code density) in-lining.
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Here's looking forward to an improved GCC optimizer.
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Pragmatics - avoid host FP hardware:
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FP operations can be implemented by either: the host's floating
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point hardware; or by emulating the FP operations using integer
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only routines. This is direct tradeoff between speed, portability
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and correctness.
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The two principal reasons for selecting portability and correctness
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over speed are:
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1 - Correctness. The assumption that FP correctness wasn't an
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issue for code being run on simulators was wrong. Instead of
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running FP tolerant (?) code, simulator users instead typically run
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very aggressive FP code sequences. The sole purpose of those
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sequences being to test the target ISA's FP implementation.
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2 - Portability. The host FP implementation is not predictable. A
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simulator modeling aggressive FP code sequences using the hosts FPU
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relies heavily on the correctness of the hosts FP implementation.
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It turns out that such trust can be misplaced. The behavior of
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host FP implementations when handling edge conditions such as SNaNs
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and exceptions varied widely.
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*/
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typedef enum
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{
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sim_fpu_class_zero,
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sim_fpu_class_snan,
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sim_fpu_class_qnan,
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sim_fpu_class_number,
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sim_fpu_class_denorm,
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sim_fpu_class_infinity,
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} sim_fpu_class;
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typedef struct _sim_fpu {
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sim_fpu_class class;
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int sign;
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unsigned64 fraction;
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int normal_exp;
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} sim_fpu;
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/* Rounding options.
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The value zero (sim_fpu_round_default) for ALU operations indicates
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that, when possible, rounding should be avoided. */
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typedef enum
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{
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sim_fpu_round_default = 0,
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sim_fpu_round_near = 1,
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sim_fpu_round_zero = 2,
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sim_fpu_round_up = 3,
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sim_fpu_round_down = 4,
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} sim_fpu_round;
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/* Options when handling denormalized numbers. */
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typedef enum
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{
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sim_fpu_denorm_default = 0,
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sim_fpu_denorm_underflow_inexact = 1,
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sim_fpu_denorm_zero = 2,
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} sim_fpu_denorm;
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/* Status values returned by FPU operators.
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When checking the result of an FP sequence (ex 32to, add, single,
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to32) the caller may either: check the return value of each FP
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operator; or form the union (OR) of the returned values and examine
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them once at the end.
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FIXME: This facility is still being developed. The choice of
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status values returned and their exact meaning may changed in the
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future. */
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typedef enum
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{
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sim_fpu_status_invalid_snan = 1,
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sim_fpu_status_invalid_qnan = 2,
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sim_fpu_status_invalid_isi = 4, /* (inf - inf) */
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sim_fpu_status_invalid_idi = 8, /* (inf / inf) */
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sim_fpu_status_invalid_zdz = 16, /* (0 / 0) */
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sim_fpu_status_invalid_imz = 32, /* (inf * 0) */
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sim_fpu_status_invalid_cvi = 64, /* convert to integer */
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sim_fpu_status_invalid_div0 = 128, /* (X / 0) */
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sim_fpu_status_invalid_cmp = 256, /* compare */
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sim_fpu_status_invalid_sqrt = 512,
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sim_fpu_status_invalid_irx = 1024, /* (inf % X) */
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sim_fpu_status_rounded = 2048,
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sim_fpu_status_inexact = 4096,
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sim_fpu_status_overflow = 8192,
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sim_fpu_status_underflow = 16384,
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sim_fpu_status_denorm = 32768,
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} sim_fpu_status;
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/* Directly map between a 32/64 bit register and the sim_fpu internal
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type.
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When converting from the 32/64 bit packed format to the sim_fpu
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internal type, the operation is exact.
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When converting from the sim_fpu internal type to 32/64 bit packed
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format, the operation may result in a loss of precision. The
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configuration macro WITH_FPU_CONVERSION controls this. By default,
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silent round to nearest is performed. Alternatively, round up,
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round down and round to zero can be performed. In a simulator
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emulating exact FPU behavior, sim_fpu_round_{32,64} should be
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called before packing the sim_fpu value. */
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INLINE_SIM_FPU (void) sim_fpu_32to (sim_fpu *f, unsigned32 s);
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INLINE_SIM_FPU (void) sim_fpu_232to (sim_fpu *f, unsigned32 h, unsigned32 l);
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INLINE_SIM_FPU (void) sim_fpu_64to (sim_fpu *f, unsigned64 d);
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INLINE_SIM_FPU (void) sim_fpu_to32 (unsigned32 *s, const sim_fpu *f);
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INLINE_SIM_FPU (void) sim_fpu_to232 (unsigned32 *h, unsigned32 *l, const sim_fpu *f);
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INLINE_SIM_FPU (void) sim_fpu_to64 (unsigned64 *d, const sim_fpu *f);
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/* Create a sim_fpu struct using raw information. (FRACTION & LSMASK
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(PRECISION-1, 0)) is assumed to contain the fraction part of the
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floating-point number. The leading bit LSBIT (PRECISION) is always
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implied. The number created can be represented by:
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(SIGN ? "-" : "+") "1." FRACTION{PRECISION-1,0} X 2 ^ NORMAL_EXP>
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You can not specify zero using this function. */
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INLINE_SIM_FPU (void) sim_fpu_fractionto (sim_fpu *f, int sign, int normal_exp, unsigned64 fraction, int precision);
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/* Reverse operation. If S is a non-zero number, discards the implied
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leading one and returns PRECISION fraction bits. No rounding is
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performed. */
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INLINE_SIM_FPU (unsigned64) sim_fpu_tofraction (const sim_fpu *s, int precision);
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/* Rounding operators.
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Force an intermediate result to an exact 32/64 bit
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representation. */
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INLINE_SIM_FPU (int) sim_fpu_round_32 (sim_fpu *f,
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sim_fpu_round round,
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sim_fpu_denorm denorm);
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INLINE_SIM_FPU (int) sim_fpu_round_64 (sim_fpu *f,
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sim_fpu_round round,
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sim_fpu_denorm denorm);
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/* Arithmetic operators.
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FIXME: In the future, additional arguments ROUNDING and BITSIZE may
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be added. */
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typedef int (sim_fpu_op1) (sim_fpu *f,
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const sim_fpu *l);
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typedef int (sim_fpu_op2) (sim_fpu *f,
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const sim_fpu *l,
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const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_add (sim_fpu *f,
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const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_sub (sim_fpu *f,
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const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_mul (sim_fpu *f,
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const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_div (sim_fpu *f,
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const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_rem (sim_fpu *f,
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const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_max (sim_fpu *f,
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const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_min (sim_fpu *f,
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const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_neg (sim_fpu *f,
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const sim_fpu *a);
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INLINE_SIM_FPU (int) sim_fpu_abs (sim_fpu *f,
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const sim_fpu *a);
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INLINE_SIM_FPU (int) sim_fpu_inv (sim_fpu *f,
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const sim_fpu *a);
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INLINE_SIM_FPU (int) sim_fpu_sqrt (sim_fpu *f,
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const sim_fpu *sqr);
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/* Conversion of integer <-> floating point. */
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INLINE_SIM_FPU (int) sim_fpu_i32to (sim_fpu *f, signed32 i,
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sim_fpu_round round);
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INLINE_SIM_FPU (int) sim_fpu_u32to (sim_fpu *f, unsigned32 u,
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sim_fpu_round round);
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INLINE_SIM_FPU (int) sim_fpu_i64to (sim_fpu *f, signed64 i,
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sim_fpu_round round);
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INLINE_SIM_FPU (int) sim_fpu_u64to (sim_fpu *f, unsigned64 u,
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sim_fpu_round round);
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#if 0
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INLINE_SIM_FPU (int) sim_fpu_i232to (sim_fpu *f, signed32 h, signed32 l,
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sim_fpu_round round);
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#endif
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#if 0
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INLINE_SIM_FPU (int) sim_fpu_u232to (sim_fpu *f, unsigned32 h, unsigned32 l,
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sim_fpu_round round);
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#endif
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INLINE_SIM_FPU (int) sim_fpu_to32i (signed32 *i, const sim_fpu *f,
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sim_fpu_round round);
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INLINE_SIM_FPU (int) sim_fpu_to32u (unsigned32 *u, const sim_fpu *f,
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sim_fpu_round round);
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INLINE_SIM_FPU (int) sim_fpu_to64i (signed64 *i, const sim_fpu *f,
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sim_fpu_round round);
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INLINE_SIM_FPU (int) sim_fpu_to64u (unsigned64 *u, const sim_fpu *f,
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sim_fpu_round round);
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#if 0
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INLINE_SIM_FPU (int) sim_fpu_to232i (signed64 *h, signed64 *l, const sim_fpu *f,
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sim_fpu_round round);
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#endif
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#if 0
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INLINE_SIM_FPU (int) sim_fpu_to232u (unsigned64 *h, unsigned64 *l, const sim_fpu *f,
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sim_fpu_round round);
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#endif
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/* Conversion of internal sim_fpu type to host double format.
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For debugging/tracing only. A SNaN is never returned. */
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/* INLINE_SIM_FPU (float) sim_fpu_2f (const sim_fpu *f); */
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INLINE_SIM_FPU (double) sim_fpu_2d (const sim_fpu *d);
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/* INLINE_SIM_FPU (void) sim_fpu_f2 (sim_fpu *f, float s); */
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INLINE_SIM_FPU (void) sim_fpu_d2 (sim_fpu *f, double d);
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/* Specific number classes.
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NB: When either, a 32/64 bit floating points is converted to
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internal format, or an internal format number is rounded to 32/64
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bit precision, a special marker is retained that indicates that the
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value was normalized. For such numbers both is_number and
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is_denorm return true. */
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INLINE_SIM_FPU (int) sim_fpu_is_nan (const sim_fpu *s); /* 1 => SNaN or QNaN */
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INLINE_SIM_FPU (int) sim_fpu_is_snan (const sim_fpu *s); /* 1 => SNaN */
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INLINE_SIM_FPU (int) sim_fpu_is_qnan (const sim_fpu *s); /* 1 => QNaN */
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INLINE_SIM_FPU (int) sim_fpu_is_zero (const sim_fpu *s);
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INLINE_SIM_FPU (int) sim_fpu_is_infinity (const sim_fpu *s);
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INLINE_SIM_FPU (int) sim_fpu_is_number (const sim_fpu *s); /* !zero */
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INLINE_SIM_FPU (int) sim_fpu_is_denorm (const sim_fpu *s); /* !zero */
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/* Floating point fields */
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INLINE_SIM_FPU (int) sim_fpu_sign (const sim_fpu *s);
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INLINE_SIM_FPU (int) sim_fpu_exp (const sim_fpu *s);
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INLINE_SIM_FPU (unsigned64) sim_fpu_fraction (const sim_fpu *s);
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INLINE_SIM_FPU (unsigned64) sim_fpu_guard (const sim_fpu *s, int is_double);
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/* Specific comparison operators
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For NaNs et al., the comparison operators will set IS to zero and
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return a nonzero result. */
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INLINE_SIM_FPU (int) sim_fpu_lt (int *is, const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_le (int *is, const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_eq (int *is, const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_ne (int *is, const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_ge (int *is, const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_gt (int *is, const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_is_lt (const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_is_le (const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_is_eq (const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_is_ne (const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_is_ge (const sim_fpu *l, const sim_fpu *r);
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INLINE_SIM_FPU (int) sim_fpu_is_gt (const sim_fpu *l, const sim_fpu *r);
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/* General number class and comparison operators.
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The result of the comparison is indicated by returning one of the
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values below. Efficient emulation of a target FP compare
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instruction can be achieved by redefining the values below to match
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corresponding target FP status bits.
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For instance. SIM_FPU_QNAN may be redefined to be the bit
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`INVALID' while SIM_FPU_NINF might be redefined as the bits
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`NEGATIVE | INFINITY | VALID'. */
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#ifndef SIM_FPU_IS_SNAN
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enum {
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SIM_FPU_IS_SNAN = 1, /* Noisy not-a-number */
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SIM_FPU_IS_QNAN = 2, /* Quiet not-a-number */
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SIM_FPU_IS_NINF = 3, /* -infinity */
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SIM_FPU_IS_PINF = 4, /* +infinity */
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SIM_FPU_IS_NNUMBER = 5, /* -number - [ -MAX .. -MIN ] */
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SIM_FPU_IS_PNUMBER = 6, /* +number - [ +MIN .. +MAX ] */
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SIM_FPU_IS_NDENORM = 7, /* -denorm - ( MIN .. 0 ) */
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SIM_FPU_IS_PDENORM = 8, /* +denorm - ( 0 .. MIN ) */
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SIM_FPU_IS_NZERO = 9, /* -0 */
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SIM_FPU_IS_PZERO = 10, /* +0 */
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};
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#endif
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INLINE_SIM_FPU (int) sim_fpu_is (const sim_fpu *l);
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INLINE_SIM_FPU (int) sim_fpu_cmp (const sim_fpu *l, const sim_fpu *r);
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/* A number of useful constants. */
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extern const sim_fpu sim_fpu_zero;
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extern const sim_fpu sim_fpu_one;
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extern const sim_fpu sim_fpu_two;
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extern const sim_fpu sim_fpu_qnan;
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extern const sim_fpu sim_fpu_max32;
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extern const sim_fpu sim_fpu_max64;
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/* Select the applicable functions for the fp_word type */
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#if WITH_TARGET_FLOATING_POINT_BITSIZE == 32
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#define sim_fpu_tofp sim_fpu_to32
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#define sim_fpu_fpto sim_fpu_32to
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#define sim_fpu_round_fp sim_fpu_round_32
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#define sim_fpu_maxfp sim_fpu_max32
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#endif
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#if WITH_TARGET_FLOATING_POINT_BITSIZE == 64
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#define sim_fpu_tofp sim_fpu_to64
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#define sim_fpu_fpto sim_fpu_64to
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#define sim_fpu_round_fp sim_fpu_round_64
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#define sim_fpu_maxfp sim_fpu_max64
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#endif
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/* For debugging */
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typedef void sim_fpu_print_func (void *, const char *, ...);
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/* Print a sim_fpu with full precision. */
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INLINE_SIM_FPU (void) sim_fpu_print_fpu (const sim_fpu *f,
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sim_fpu_print_func *print,
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void *arg);
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/* Print a sim_fpu with `n' trailing digits. */
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INLINE_SIM_FPU (void) sim_fpu_printn_fpu (const sim_fpu *f,
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sim_fpu_print_func *print,
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int digits,
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void *arg);
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INLINE_SIM_FPU (void) sim_fpu_print_status (int status,
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sim_fpu_print_func *print,
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void *arg);
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#if H_REVEALS_MODULE_P (SIM_FPU_INLINE)
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#include "sim-fpu.c"
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#endif
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#endif
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