1 /*
2 * Helpers for emulation of FPU-related MIPS instructions.
3 *
4 * Copyright (C) 2004-2005 Jocelyn Mayer
5 *
6 * SPDX-License-Identifier: LGPL-2.1-or-later
7 */
8 #include "fpu/softfloat-helpers.h"
9 #include "cpu.h"
10
11 extern const FloatRoundMode ieee_rm[4];
12
13 uint32_t float_class_s(uint32_t arg, float_status *fst);
14 uint64_t float_class_d(uint64_t arg, float_status *fst);
15
restore_rounding_mode(CPUMIPSState * env)16 static inline void restore_rounding_mode(CPUMIPSState *env)
17 {
18 set_float_rounding_mode(ieee_rm[env->active_fpu.fcr31 & 3],
19 &env->active_fpu.fp_status);
20 }
21
restore_flush_mode(CPUMIPSState * env)22 static inline void restore_flush_mode(CPUMIPSState *env)
23 {
24 set_flush_to_zero((env->active_fpu.fcr31 & (1 << FCR31_FS)) != 0,
25 &env->active_fpu.fp_status);
26 }
27
restore_snan_bit_mode(CPUMIPSState * env)28 static inline void restore_snan_bit_mode(CPUMIPSState *env)
29 {
30 bool nan2008 = env->active_fpu.fcr31 & (1 << FCR31_NAN2008);
31
32 /*
33 * With nan2008, SNaNs are silenced in the usual way.
34 * Before that, SNaNs are not silenced; default nans are produced.
35 */
36 set_snan_bit_is_one(!nan2008, &env->active_fpu.fp_status);
37 set_default_nan_mode(!nan2008, &env->active_fpu.fp_status);
38 }
39
restore_fp_status(CPUMIPSState * env)40 static inline void restore_fp_status(CPUMIPSState *env)
41 {
42 restore_rounding_mode(env);
43 restore_flush_mode(env);
44 restore_snan_bit_mode(env);
45 }
46
fp_reset(CPUMIPSState * env)47 static inline void fp_reset(CPUMIPSState *env)
48 {
49 restore_fp_status(env);
50
51 /*
52 * According to MIPS specifications, if one of the two operands is
53 * a sNaN, a new qNaN has to be generated. This is done in
54 * floatXX_silence_nan(). For qNaN inputs the specifications
55 * says: "When possible, this QNaN result is one of the operand QNaN
56 * values." In practice it seems that most implementations choose
57 * the first operand if both operands are qNaN. In short this gives
58 * the following rules:
59 * 1. A if it is signaling
60 * 2. B if it is signaling
61 * 3. A (quiet)
62 * 4. B (quiet)
63 * A signaling NaN is always silenced before returning it.
64 */
65 set_float_2nan_prop_rule(float_2nan_prop_s_ab,
66 &env->active_fpu.fp_status);
67 }
68
69 /* MSA */
70
71 enum CPUMIPSMSADataFormat {
72 DF_BYTE = 0,
73 DF_HALF,
74 DF_WORD,
75 DF_DOUBLE
76 };
77
restore_msa_fp_status(CPUMIPSState * env)78 static inline void restore_msa_fp_status(CPUMIPSState *env)
79 {
80 float_status *status = &env->active_tc.msa_fp_status;
81 int rounding_mode = (env->active_tc.msacsr & MSACSR_RM_MASK) >> MSACSR_RM;
82 bool flush_to_zero = (env->active_tc.msacsr & MSACSR_FS_MASK) != 0;
83
84 set_float_rounding_mode(ieee_rm[rounding_mode], status);
85 set_flush_to_zero(flush_to_zero, status);
86 set_flush_inputs_to_zero(flush_to_zero, status);
87 }
88