softfloat: Implement run-time-configurable meaning of signaling NaN bit

This patch modifies SoftFloat library so that it can be configured in
run-time in relation to the meaning of signaling NaN bit, while, at the
same time, strictly preserving its behavior on all existing platforms.

Background:

In floating-point calculations, there is a need for denoting undefined or
unrepresentable values. This is achieved by defining certain floating-point
numerical values to be NaNs (which stands for "not a number"). For additional
reasons, virtually all modern floating-point unit implementations use two
kinds of NaNs: quiet and signaling. The binary representations of these two
kinds of NaNs, as a rule, differ only in one bit (that bit is, traditionally,
the first bit of mantissa).

Up to 2008, standards for floating-point did not specify all details about
binary representation of NaNs. More specifically, the meaning of the bit
that is used for distinguishing between signaling and quiet NaNs was not
strictly prescribed. (IEEE 754-2008 was the first floating-point standard
that defined that meaning clearly, see [1], p. 35) As a result, different
platforms took different approaches, and that presented considerable
challenge for multi-platform emulators like QEMU.

Mips platform represents the most complex case among QEMU-supported
platforms regarding signaling NaN bit. Up to the Release 6 of Mips
architecture, "1" in signaling NaN bit denoted signaling NaN, which is
opposite to IEEE 754-2008 standard. From Release 6 on, Mips architecture
adopted IEEE standard prescription, and "0" denotes signaling NaN. On top of
that, Mips architecture for SIMD (also known as MSA, or vector instructions)
also specifies signaling bit in accordance to IEEE standard. MSA unit can be
implemented with both pre-Release 6 and Release 6 main processor units.

QEMU uses SoftFloat library to implement various floating-point-related
instructions on all platforms. The current QEMU implementation allows for
defining meaning of signaling NaN bit during build time, and is implemented
via preprocessor macro called SNAN_BIT_IS_ONE.

On the other hand, the change in this patch enables SoftFloat library to be
configured in run-time. This configuration is meant to occur during CPU
initialization, at the moment when it is definitely known what desired
behavior for particular CPU (or any additional FPUs) is.

The change is implemented so that it is consistent with existing
implementation of similar cases. This means that structure float_status is
used for passing the information about desired signaling NaN bit on each
invocation of SoftFloat functions. The additional field in float_status is
called snan_bit_is_one, which supersedes macro SNAN_BIT_IS_ONE.

IMPORTANT:

This change is not meant to create any change in emulator behavior or
functionality on any platform. It just provides the means for SoftFloat
library to be used in a more flexible way - in other words, it will just
prepare SoftFloat library for usage related to Mips platform and its
specifics regarding signaling bit meaning, which is done in some of
subsequent patches from this series.

Further break down of changes:

  1) Added field snan_bit_is_one to the structure float_status, and
     correspondent setter function set_snan_bit_is_one().

  2) Constants <float16|float32|float64|floatx80|float128>_default_nan
     (used both internally and externally) converted to functions
     <float16|float32|float64|floatx80|float128>_default_nan(float_status*).
     This is necessary since they are dependent on signaling bit meaning.
     At the same time, for the sake of code cleanup and simplicity, constants
     <floatx80|float128>_default_nan_<low|high> (used only internally within
     SoftFloat library) are removed, as not needed.

  3) Added a float_status* argument to SoftFloat library functions
     XXX_is_quiet_nan(XXX a_), XXX_is_signaling_nan(XXX a_),
     XXX_maybe_silence_nan(XXX a_). This argument must be present in
     order to enable correct invocation of new version of functions
     XXX_default_nan(). (XXX is <float16|float32|float64|floatx80|float128>
     here)

  4) Updated code for all platforms to reflect changes in SoftFloat library.
     This change is twofolds: it includes modifications of SoftFloat library
     functions invocations, and an addition of invocation of function
     set_snan_bit_is_one() during CPU initialization, with arguments that
     are appropriate for each particular platform. It was established that
     all platforms zero their main CPU data structures, so snan_bit_is_one(0)
     in appropriate places is not added, as it is not needed.

[1] "IEEE Standard for Floating-Point Arithmetic",
    IEEE Computer Society, August 29, 2008.

Signed-off-by: Thomas Schwinge <thomas@codesourcery.com>
Signed-off-by: Maciej W. Rozycki <macro@codesourcery.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Tested-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Reviewed-by: Leon Alrae <leon.alrae@imgtec.com>
Tested-by: Leon Alrae <leon.alrae@imgtec.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
[leon.alrae@imgtec.com:
 * cherry-picked 2 chunks from patch #2 to fix compilation warnings]
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>

6 files changed, 71 insertions, 50 deletions

diff --git a/target-mips/cpu.h b/target-mips/cpu.h
index 4ce9d47661..b593f3b7b9 100644
--- a/target-mips/cpu.h
+++ b/target-mips/cpu.h
@@ -825,6 +825,11 @@ void cpu_mips_soft_irq(CPUMIPSState *env, int irq, int level);
 /* helper.c */
 int mips_cpu_handle_mmu_fault(CPUState *cpu, vaddr address, int rw,
                               int mmu_idx);
+
+/* op_helper.c */
+uint32_t float_class_s(uint32_t arg, float_status *fst);
+uint64_t float_class_d(uint64_t arg, float_status *fst);
+
 #if !defined(CONFIG_USER_ONLY)
 void r4k_invalidate_tlb (CPUMIPSState *env, int idx, int use_extra);
 hwaddr cpu_mips_translate_address (CPUMIPSState *env, target_ulong address,
diff --git a/target-mips/helper.h b/target-mips/helper.h
index 594341d258..854617704f 100644
--- a/target-mips/helper.h
+++ b/target-mips/helper.h
@@ -222,8 +222,8 @@ DEF_HELPER_2(float_cvtw_d, i32, env, i64)
 DEF_HELPER_3(float_addr_ps, i64, env, i64, i64)
 DEF_HELPER_3(float_mulr_ps, i64, env, i64, i64)
 
-DEF_HELPER_FLAGS_1(float_class_s, TCG_CALL_NO_RWG_SE, i32, i32)
-DEF_HELPER_FLAGS_1(float_class_d, TCG_CALL_NO_RWG_SE, i64, i64)
+DEF_HELPER_FLAGS_2(float_class_s, TCG_CALL_NO_RWG_SE, i32, env, i32)
+DEF_HELPER_FLAGS_2(float_class_d, TCG_CALL_NO_RWG_SE, i64, env, i64)
 
 #define FOP_PROTO(op)                                     \
 DEF_HELPER_4(float_ ## op ## _s, i32, env, i32, i32, i32) \
diff --git a/target-mips/msa_helper.c b/target-mips/msa_helper.c
index ae92fcbe28..1fdb0d9792 100644
--- a/target-mips/msa_helper.c
+++ b/target-mips/msa_helper.c
@@ -1495,11 +1495,11 @@ MSA_UNOP_DF(pcnt)
 #define FLOAT_ONE32 make_float32(0x3f8 << 20)
 #define FLOAT_ONE64 make_float64(0x3ffULL << 52)
 
-#define FLOAT_SNAN16 (float16_default_nan ^ 0x0220)
+#define FLOAT_SNAN16(s) (float16_default_nan(s) ^ 0x0220)
         /* 0x7c20 */
-#define FLOAT_SNAN32 (float32_default_nan ^ 0x00400020)
+#define FLOAT_SNAN32(s) (float32_default_nan(s) ^ 0x00400020)
         /* 0x7f800020 */
-#define FLOAT_SNAN64 (float64_default_nan ^ 0x0008000000000020ULL)
+#define FLOAT_SNAN64(s) (float64_default_nan(s) ^ 0x0008000000000020ULL)
         /* 0x7ff0000000000020 */
 
 static inline void clear_msacsr_cause(CPUMIPSState *env)
@@ -1612,7 +1612,7 @@ static inline float16 float16_from_float32(int32_t a, flag ieee,
       float16 f_val;
 
       f_val = float32_to_float16((float32)a, ieee, status);
-      f_val = float16_maybe_silence_nan(f_val);
+      f_val = float16_maybe_silence_nan(f_val, status);
 
       return a < 0 ? (f_val | (1 << 15)) : f_val;
 }
@@ -1622,7 +1622,7 @@ static inline float32 float32_from_float64(int64_t a, float_status *status)
       float32 f_val;
 
       f_val = float64_to_float32((float64)a, status);
-      f_val = float32_maybe_silence_nan(f_val);
+      f_val = float32_maybe_silence_nan(f_val, status);
 
       return a < 0 ? (f_val | (1 << 31)) : f_val;
 }
@@ -1633,7 +1633,7 @@ static inline float32 float32_from_float16(int16_t a, flag ieee,
       float32 f_val;
 
       f_val = float16_to_float32((float16)a, ieee, status);
-      f_val = float32_maybe_silence_nan(f_val);
+      f_val = float32_maybe_silence_nan(f_val, status);
 
       return a < 0 ? (f_val | (1 << 31)) : f_val;
 }
@@ -1643,7 +1643,7 @@ static inline float64 float64_from_float32(int32_t a, float_status *status)
       float64 f_val;
 
       f_val = float32_to_float64((float64)a, status);
-      f_val = float64_maybe_silence_nan(f_val);
+      f_val = float64_maybe_silence_nan(f_val, status);
 
       return a < 0 ? (f_val | (1ULL << 63)) : f_val;
 }
@@ -1789,7 +1789,7 @@ static inline int32_t float64_to_q32(float64 a, float_status *status)
         c = update_msacsr(env, CLEAR_IS_INEXACT, 0);                        \
                                                                             \
         if (get_enabled_exceptions(env, c)) {                               \
-            DEST = ((FLOAT_SNAN ## BITS >> 6) << 6) | c;                    \
+            DEST = ((FLOAT_SNAN ## BITS(status) >> 6) << 6) | c;            \
         }                                                                   \
     } while (0)
 
@@ -2388,7 +2388,7 @@ void helper_msa_fsne_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         c = update_msacsr(env, 0, IS_DENORMAL(DEST, BITS));                 \
                                                                             \
         if (get_enabled_exceptions(env, c)) {                               \
-            DEST = ((FLOAT_SNAN ## BITS >> 6) << 6) | c;                    \
+            DEST = ((FLOAT_SNAN ## BITS(status) >> 6) << 6) | c;            \
         }                                                                   \
     } while (0)
 
@@ -2524,7 +2524,7 @@ void helper_msa_fdiv_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         c = update_msacsr(env, 0, IS_DENORMAL(DEST, BITS));                 \
                                                                             \
         if (get_enabled_exceptions(env, c)) {                               \
-            DEST = ((FLOAT_SNAN ## BITS >> 6) << 6) | c;                    \
+            DEST = ((FLOAT_SNAN ## BITS(status) >> 6) << 6) | c;            \
         }                                                                   \
     } while (0)
 
@@ -2643,7 +2643,7 @@ void helper_msa_fexp2_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         c = update_msacsr(env, 0, IS_DENORMAL(DEST, BITS));                 \
                                                                             \
         if (get_enabled_exceptions(env, c)) {                               \
-            DEST = ((FLOAT_SNAN ## BITS >> 6) << 6) | c;                    \
+            DEST = ((FLOAT_SNAN ## BITS(status) >> 6) << 6) | c;            \
         }                                                                   \
     } while (0)
 
@@ -2694,7 +2694,7 @@ void helper_msa_fexdo_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         c = update_msacsr(env, CLEAR_FS_UNDERFLOW, 0);                      \
                                                                             \
         if (get_enabled_exceptions(env, c)) {                               \
-            DEST = ((FLOAT_SNAN ## XBITS >> 6) << 6) | c;                   \
+            DEST = ((FLOAT_SNAN ## XBITS(status) >> 6) << 6) | c;           \
         }                                                                   \
     } while (0)
 
@@ -2731,9 +2731,9 @@ void helper_msa_ftq_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
     msa_move_v(pwd, pwx);
 }
 
-#define NUMBER_QNAN_PAIR(ARG1, ARG2, BITS)      \
-    !float ## BITS ## _is_any_nan(ARG1)         \
-    && float ## BITS ## _is_quiet_nan(ARG2)
+#define NUMBER_QNAN_PAIR(ARG1, ARG2, BITS, STATUS)      \
+    !float ## BITS ## _is_any_nan(ARG1)                 \
+    && float ## BITS ## _is_quiet_nan(ARG2, STATUS)
 
 #define MSA_FLOAT_MAXOP(DEST, OP, ARG1, ARG2, BITS)                         \
     do {                                                                    \
@@ -2745,18 +2745,18 @@ void helper_msa_ftq_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         c = update_msacsr(env, 0, 0);                                       \
                                                                             \
         if (get_enabled_exceptions(env, c)) {                               \
-            DEST = ((FLOAT_SNAN ## BITS >> 6) << 6) | c;                    \
+            DEST = ((FLOAT_SNAN ## BITS(status) >> 6) << 6) | c;            \
         }                                                                   \
     } while (0)
 
-#define FMAXMIN_A(F, G, X, _S, _T, BITS)                            \
+#define FMAXMIN_A(F, G, X, _S, _T, BITS, STATUS)                    \
     do {                                                            \
         uint## BITS ##_t S = _S, T = _T;                            \
         uint## BITS ##_t as, at, xs, xt, xd;                        \
-        if (NUMBER_QNAN_PAIR(S, T, BITS)) {                         \
+        if (NUMBER_QNAN_PAIR(S, T, BITS, STATUS)) {                 \
             T = S;                                                  \
         }                                                           \
-        else if (NUMBER_QNAN_PAIR(T, S, BITS)) {                    \
+        else if (NUMBER_QNAN_PAIR(T, S, BITS, STATUS)) {            \
             S = T;                                                  \
         }                                                           \
         as = float## BITS ##_abs(S);                                \
@@ -2770,6 +2770,7 @@ void helper_msa_ftq_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
 void helper_msa_fmin_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         uint32_t ws, uint32_t wt)
 {
+    float_status *status = &env->active_tc.msa_fp_status;
     wr_t wx, *pwx = &wx;
     wr_t *pwd = &(env->active_fpu.fpr[wd].wr);
     wr_t *pws = &(env->active_fpu.fpr[ws].wr);
@@ -2781,9 +2782,9 @@ void helper_msa_fmin_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
     switch (df) {
     case DF_WORD:
         for (i = 0; i < DF_ELEMENTS(DF_WORD); i++) {
-            if (NUMBER_QNAN_PAIR(pws->w[i], pwt->w[i], 32)) {
+            if (NUMBER_QNAN_PAIR(pws->w[i], pwt->w[i], 32, status)) {
                 MSA_FLOAT_MAXOP(pwx->w[i], min, pws->w[i], pws->w[i], 32);
-            } else if (NUMBER_QNAN_PAIR(pwt->w[i], pws->w[i], 32)) {
+            } else if (NUMBER_QNAN_PAIR(pwt->w[i], pws->w[i], 32, status)) {
                 MSA_FLOAT_MAXOP(pwx->w[i], min, pwt->w[i], pwt->w[i], 32);
             } else {
                 MSA_FLOAT_MAXOP(pwx->w[i], min, pws->w[i], pwt->w[i], 32);
@@ -2792,9 +2793,9 @@ void helper_msa_fmin_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         break;
     case DF_DOUBLE:
         for (i = 0; i < DF_ELEMENTS(DF_DOUBLE); i++) {
-            if (NUMBER_QNAN_PAIR(pws->d[i], pwt->d[i], 64)) {
+            if (NUMBER_QNAN_PAIR(pws->d[i], pwt->d[i], 64, status)) {
                 MSA_FLOAT_MAXOP(pwx->d[i], min, pws->d[i], pws->d[i], 64);
-            } else if (NUMBER_QNAN_PAIR(pwt->d[i], pws->d[i], 64)) {
+            } else if (NUMBER_QNAN_PAIR(pwt->d[i], pws->d[i], 64, status)) {
                 MSA_FLOAT_MAXOP(pwx->d[i], min, pwt->d[i], pwt->d[i], 64);
             } else {
                 MSA_FLOAT_MAXOP(pwx->d[i], min, pws->d[i], pwt->d[i], 64);
@@ -2813,6 +2814,7 @@ void helper_msa_fmin_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
 void helper_msa_fmin_a_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         uint32_t ws, uint32_t wt)
 {
+    float_status *status = &env->active_tc.msa_fp_status;
     wr_t wx, *pwx = &wx;
     wr_t *pwd = &(env->active_fpu.fpr[wd].wr);
     wr_t *pws = &(env->active_fpu.fpr[ws].wr);
@@ -2824,12 +2826,12 @@ void helper_msa_fmin_a_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
     switch (df) {
     case DF_WORD:
         for (i = 0; i < DF_ELEMENTS(DF_WORD); i++) {
-            FMAXMIN_A(min, max, pwx->w[i], pws->w[i], pwt->w[i], 32);
+            FMAXMIN_A(min, max, pwx->w[i], pws->w[i], pwt->w[i], 32, status);
         }
         break;
     case DF_DOUBLE:
         for (i = 0; i < DF_ELEMENTS(DF_DOUBLE); i++) {
-            FMAXMIN_A(min, max, pwx->d[i], pws->d[i], pwt->d[i], 64);
+            FMAXMIN_A(min, max, pwx->d[i], pws->d[i], pwt->d[i], 64, status);
         }
         break;
     default:
@@ -2844,6 +2846,7 @@ void helper_msa_fmin_a_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
 void helper_msa_fmax_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         uint32_t ws, uint32_t wt)
 {
+    float_status *status = &env->active_tc.msa_fp_status;
     wr_t wx, *pwx = &wx;
     wr_t *pwd = &(env->active_fpu.fpr[wd].wr);
     wr_t *pws = &(env->active_fpu.fpr[ws].wr);
@@ -2855,9 +2858,9 @@ void helper_msa_fmax_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
     switch (df) {
     case DF_WORD:
         for (i = 0; i < DF_ELEMENTS(DF_WORD); i++) {
-            if (NUMBER_QNAN_PAIR(pws->w[i], pwt->w[i], 32)) {
+            if (NUMBER_QNAN_PAIR(pws->w[i], pwt->w[i], 32, status)) {
                 MSA_FLOAT_MAXOP(pwx->w[i], max, pws->w[i], pws->w[i], 32);
-            } else if (NUMBER_QNAN_PAIR(pwt->w[i], pws->w[i], 32)) {
+            } else if (NUMBER_QNAN_PAIR(pwt->w[i], pws->w[i], 32, status)) {
                 MSA_FLOAT_MAXOP(pwx->w[i], max, pwt->w[i], pwt->w[i], 32);
             } else {
                 MSA_FLOAT_MAXOP(pwx->w[i], max, pws->w[i], pwt->w[i], 32);
@@ -2866,9 +2869,9 @@ void helper_msa_fmax_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         break;
     case DF_DOUBLE:
         for (i = 0; i < DF_ELEMENTS(DF_DOUBLE); i++) {
-            if (NUMBER_QNAN_PAIR(pws->d[i], pwt->d[i], 64)) {
+            if (NUMBER_QNAN_PAIR(pws->d[i], pwt->d[i], 64, status)) {
                 MSA_FLOAT_MAXOP(pwx->d[i], max, pws->d[i], pws->d[i], 64);
-            } else if (NUMBER_QNAN_PAIR(pwt->d[i], pws->d[i], 64)) {
+            } else if (NUMBER_QNAN_PAIR(pwt->d[i], pws->d[i], 64, status)) {
                 MSA_FLOAT_MAXOP(pwx->d[i], max, pwt->d[i], pwt->d[i], 64);
             } else {
                 MSA_FLOAT_MAXOP(pwx->d[i], max, pws->d[i], pwt->d[i], 64);
@@ -2887,6 +2890,7 @@ void helper_msa_fmax_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
 void helper_msa_fmax_a_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         uint32_t ws, uint32_t wt)
 {
+    float_status *status = &env->active_tc.msa_fp_status;
     wr_t wx, *pwx = &wx;
     wr_t *pwd = &(env->active_fpu.fpr[wd].wr);
     wr_t *pws = &(env->active_fpu.fpr[ws].wr);
@@ -2898,12 +2902,12 @@ void helper_msa_fmax_a_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
     switch (df) {
     case DF_WORD:
         for (i = 0; i < DF_ELEMENTS(DF_WORD); i++) {
-            FMAXMIN_A(max, min, pwx->w[i], pws->w[i], pwt->w[i], 32);
+            FMAXMIN_A(max, min, pwx->w[i], pws->w[i], pwt->w[i], 32, status);
         }
         break;
     case DF_DOUBLE:
         for (i = 0; i < DF_ELEMENTS(DF_DOUBLE); i++) {
-            FMAXMIN_A(max, min, pwx->d[i], pws->d[i], pwt->d[i], 64);
+            FMAXMIN_A(max, min, pwx->d[i], pws->d[i], pwt->d[i], 64, status);
         }
         break;
     default:
@@ -2918,16 +2922,18 @@ void helper_msa_fmax_a_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
 void helper_msa_fclass_df(CPUMIPSState *env, uint32_t df,
         uint32_t wd, uint32_t ws)
 {
+    float_status* status = &env->active_tc.msa_fp_status;
+
     wr_t *pwd = &(env->active_fpu.fpr[wd].wr);
     wr_t *pws = &(env->active_fpu.fpr[ws].wr);
     if (df == DF_WORD) {
-        pwd->w[0] = helper_float_class_s(pws->w[0]);
-        pwd->w[1] = helper_float_class_s(pws->w[1]);
-        pwd->w[2] = helper_float_class_s(pws->w[2]);
-        pwd->w[3] = helper_float_class_s(pws->w[3]);
+        pwd->w[0] = float_class_s(pws->w[0], status);
+        pwd->w[1] = float_class_s(pws->w[1], status);
+        pwd->w[2] = float_class_s(pws->w[2], status);
+        pwd->w[3] = float_class_s(pws->w[3], status);
     } else {
-        pwd->d[0] = helper_float_class_d(pws->d[0]);
-        pwd->d[1] = helper_float_class_d(pws->d[1]);
+        pwd->d[0] = float_class_d(pws->d[0], status);
+        pwd->d[1] = float_class_d(pws->d[1], status);
     }
 }
 
@@ -2941,7 +2947,7 @@ void helper_msa_fclass_df(CPUMIPSState *env, uint32_t df,
         c = update_msacsr(env, CLEAR_FS_UNDERFLOW, 0);                      \
                                                                             \
         if (get_enabled_exceptions(env, c)) {                               \
-            DEST = ((FLOAT_SNAN ## BITS >> 6) << 6) | c;                    \
+            DEST = ((FLOAT_SNAN ## BITS(status) >> 6) << 6) | c;            \
         } else if (float ## BITS ## _is_any_nan(ARG)) {                     \
             DEST = 0;                                                       \
         }                                                                   \
@@ -3045,12 +3051,12 @@ void helper_msa_fsqrt_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         set_float_exception_flags(0, status);                               \
         DEST = float ## BITS ## _ ## div(FLOAT_ONE ## BITS, ARG, status);   \
         c = update_msacsr(env, float ## BITS ## _is_infinity(ARG) ||        \
-                          float ## BITS ## _is_quiet_nan(DEST) ?            \
+                          float ## BITS ## _is_quiet_nan(DEST, status) ?    \
                           0 : RECIPROCAL_INEXACT,                           \
                           IS_DENORMAL(DEST, BITS));                         \
                                                                             \
         if (get_enabled_exceptions(env, c)) {                               \
-            DEST = ((FLOAT_SNAN ## BITS >> 6) << 6) | c;                    \
+            DEST = ((FLOAT_SNAN ## BITS(status) >> 6) << 6) | c;            \
         }                                                                   \
     } while (0)
 
@@ -3166,7 +3172,7 @@ void helper_msa_frint_df(CPUMIPSState *env, uint32_t df, uint32_t wd,
         c = update_msacsr(env, 0, IS_DENORMAL(DEST, BITS));                 \
                                                                             \
         if (get_enabled_exceptions(env, c)) {                               \
-            DEST = ((FLOAT_SNAN ## BITS >> 6) << 6) | c;                    \
+            DEST = ((FLOAT_SNAN ## BITS(status) >> 6) << 6) | c;            \
         }                                                                   \
     } while (0)
 
diff --git a/target-mips/op_helper.c b/target-mips/op_helper.c
index 1ae1dda0af..97dffa2b7e 100644
--- a/target-mips/op_helper.c
+++ b/target-mips/op_helper.c
@@ -2659,7 +2659,7 @@ uint64_t helper_float_cvtd_s(CPUMIPSState *env, uint32_t fst0)
     uint64_t fdt2;
 
     fdt2 = float32_to_float64(fst0, &env->active_fpu.fp_status);
-    fdt2 = float64_maybe_silence_nan(fdt2);
+    fdt2 = float64_maybe_silence_nan(fdt2, &env->active_fpu.fp_status);
     update_fcr31(env, GETPC());
     return fdt2;
 }
@@ -2749,7 +2749,7 @@ uint32_t helper_float_cvts_d(CPUMIPSState *env, uint64_t fdt0)
     uint32_t fst2;
 
     fst2 = float64_to_float32(fdt0, &env->active_fpu.fp_status);
-    fst2 = float32_maybe_silence_nan(fst2);
+    fst2 = float32_maybe_silence_nan(fst2, &env->active_fpu.fp_status);
     update_fcr31(env, GETPC());
     return fst2;
 }
@@ -3199,11 +3199,12 @@ FLOAT_RINT(rint_d, 64)
 #define FLOAT_CLASS_POSITIVE_ZERO      0x200
 
 #define FLOAT_CLASS(name, bits)                                      \
-uint ## bits ## _t helper_float_ ## name (uint ## bits ## _t arg)    \
+uint ## bits ## _t float_ ## name (uint ## bits ## _t arg,           \
+                                   float_status *status)             \
 {                                                                    \
-    if (float ## bits ## _is_signaling_nan(arg)) {                   \
+    if (float ## bits ## _is_signaling_nan(arg, status)) {           \
         return FLOAT_CLASS_SIGNALING_NAN;                            \
-    } else if (float ## bits ## _is_quiet_nan(arg)) {                \
+    } else if (float ## bits ## _is_quiet_nan(arg, status)) {        \
         return FLOAT_CLASS_QUIET_NAN;                                \
     } else if (float ## bits ## _is_neg(arg)) {                      \
         if (float ## bits ## _is_infinity(arg)) {                    \
@@ -3226,6 +3227,12 @@ uint ## bits ## _t helper_float_ ## name (uint ## bits ## _t arg)    \
             return FLOAT_CLASS_POSITIVE_NORMAL;                      \
         }                                                            \
     }                                                                \
+}                                                                    \
+                                                                     \
+uint ## bits ## _t helper_float_ ## name (CPUMIPSState *env,         \
+                                          uint ## bits ## _t arg)    \
+{                                                                    \
+    return float_ ## name(arg, &env->active_fpu.fp_status);          \
 }
 
 FLOAT_CLASS(class_s, 32)
diff --git a/target-mips/translate.c b/target-mips/translate.c
index aaa1d02683..a1a9f75294 100644
--- a/target-mips/translate.c
+++ b/target-mips/translate.c
@@ -9121,7 +9121,7 @@ static void gen_farith (DisasContext *ctx, enum fopcode op1,
         {
             TCGv_i32 fp0 = tcg_temp_new_i32();
             gen_load_fpr32(ctx, fp0, fs);
-            gen_helper_float_class_s(fp0, fp0);
+            gen_helper_float_class_s(fp0, cpu_env, fp0);
             gen_store_fpr32(ctx, fp0, fd);
             tcg_temp_free_i32(fp0);
         }
@@ -9619,7 +9619,7 @@ static void gen_farith (DisasContext *ctx, enum fopcode op1,
         {
             TCGv_i64 fp0 = tcg_temp_new_i64();
             gen_load_fpr64(ctx, fp0, fs);
-            gen_helper_float_class_d(fp0, fp0);
+            gen_helper_float_class_d(fp0, cpu_env, fp0);
             gen_store_fpr64(ctx, fp0, fd);
             tcg_temp_free_i64(fp0);
         }
@@ -20142,6 +20142,7 @@ void cpu_state_reset(CPUMIPSState *env)
     env->CP0_PageGrain = env->cpu_model->CP0_PageGrain;
     env->active_fpu.fcr0 = env->cpu_model->CP1_fcr0;
     env->active_fpu.fcr31 = env->cpu_model->CP1_fcr31;
+    set_snan_bit_is_one(1, &env->active_fpu.fp_status);
     env->msair = env->cpu_model->MSAIR;
     env->insn_flags = env->cpu_model->insn_flags;
 
diff --git a/target-mips/translate_init.c b/target-mips/translate_init.c
index 5af077d0de..e81a831117 100644
--- a/target-mips/translate_init.c
+++ b/target-mips/translate_init.c
@@ -892,4 +892,6 @@ static void msa_reset(CPUMIPSState *env)
 
     /* clear float_status nan mode */
     set_default_nan_mode(0, &env->active_tc.msa_fp_status);
+
+    set_snan_bit_is_one(1, &env->active_tc.msa_fp_status);
 }