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>

1 files changed, 264 insertions, 285 deletions

diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
index a4cbdad452..39095e542f 100644
--- a/fpu/softfloat-specialize.h
+++ b/fpu/softfloat-specialize.h
@@ -79,16 +79,6 @@ this code that are retained.
  * version 2 or later. See the COPYING file in the top-level directory.
  */
 
-/* Does the target distinguish signaling NaNs from non-signaling NaNs
- * by setting the most significant bit of the mantissa for a signaling NaN?
- * (The more common choice is to have it be zero for SNaN and one for QNaN.)
- */
-#if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
-#define SNAN_BIT_IS_ONE 1
-#else
-#define SNAN_BIT_IS_ONE 0
-#endif
-
 #if defined(TARGET_XTENSA)
 /* Define for architectures which deviate from IEEE in not supporting
  * signaling NaNs (so all NaNs are treated as quiet).
@@ -99,73 +89,94 @@ this code that are retained.
 /*----------------------------------------------------------------------------
 | The pattern for a default generated half-precision NaN.
 *----------------------------------------------------------------------------*/
+float16 float16_default_nan(float_status *status)
+{
 #if defined(TARGET_ARM)
-const float16 float16_default_nan = const_float16(0x7E00);
-#elif SNAN_BIT_IS_ONE
-const float16 float16_default_nan = const_float16(0x7DFF);
+    return const_float16(0x7E00);
 #else
-const float16 float16_default_nan = const_float16(0xFE00);
+    if (status->snan_bit_is_one) {
+        return const_float16(0x7DFF);
+    } else {
+        return const_float16(0xFE00);
+    }
 #endif
+}
 
 /*----------------------------------------------------------------------------
 | The pattern for a default generated single-precision NaN.
 *----------------------------------------------------------------------------*/
+float32 float32_default_nan(float_status *status)
+{
 #if defined(TARGET_SPARC)
-const float32 float32_default_nan = const_float32(0x7FFFFFFF);
+    return const_float32(0x7FFFFFFF);
 #elif defined(TARGET_PPC) || defined(TARGET_ARM) || defined(TARGET_ALPHA) || \
       defined(TARGET_XTENSA) || defined(TARGET_S390X) || defined(TARGET_TRICORE)
-const float32 float32_default_nan = const_float32(0x7FC00000);
-#elif SNAN_BIT_IS_ONE
-const float32 float32_default_nan = const_float32(0x7FBFFFFF);
+    return const_float32(0x7FC00000);
 #else
-const float32 float32_default_nan = const_float32(0xFFC00000);
+    if (status->snan_bit_is_one) {
+        return const_float32(0x7FBFFFFF);
+    } else {
+        return const_float32(0xFFC00000);
+    }
 #endif
+}
 
 /*----------------------------------------------------------------------------
 | The pattern for a default generated double-precision NaN.
 *----------------------------------------------------------------------------*/
+float64 float64_default_nan(float_status *status)
+{
 #if defined(TARGET_SPARC)
-const float64 float64_default_nan = const_float64(LIT64( 0x7FFFFFFFFFFFFFFF ));
+    return const_float64(LIT64(0x7FFFFFFFFFFFFFFF));
 #elif defined(TARGET_PPC) || defined(TARGET_ARM) || defined(TARGET_ALPHA) || \
       defined(TARGET_S390X)
-const float64 float64_default_nan = const_float64(LIT64( 0x7FF8000000000000 ));
-#elif SNAN_BIT_IS_ONE
-const float64 float64_default_nan = const_float64(LIT64(0x7FF7FFFFFFFFFFFF));
+    return const_float64(LIT64(0x7FF8000000000000));
 #else
-const float64 float64_default_nan = const_float64(LIT64( 0xFFF8000000000000 ));
+    if (status->snan_bit_is_one) {
+        return const_float64(LIT64(0x7FF7FFFFFFFFFFFF));
+    } else {
+        return const_float64(LIT64(0xFFF8000000000000));
+    }
 #endif
+}
 
 /*----------------------------------------------------------------------------
 | The pattern for a default generated extended double-precision NaN.
 *----------------------------------------------------------------------------*/
-#if SNAN_BIT_IS_ONE
-#define floatx80_default_nan_high 0x7FFF
-#define floatx80_default_nan_low  LIT64(0xBFFFFFFFFFFFFFFF)
-#else
-#define floatx80_default_nan_high 0xFFFF
-#define floatx80_default_nan_low  LIT64( 0xC000000000000000 )
-#endif
+floatx80 floatx80_default_nan(float_status *status)
+{
+    floatx80 r;
 
-const floatx80 floatx80_default_nan
-    = make_floatx80_init(floatx80_default_nan_high, floatx80_default_nan_low);
+    if (status->snan_bit_is_one) {
+        r.low = LIT64(0xBFFFFFFFFFFFFFFF);
+        r.high = 0x7FFF;
+    } else {
+        r.low = LIT64(0xC000000000000000);
+        r.high = 0xFFFF;
+    }
+    return r;
+}
 
 /*----------------------------------------------------------------------------
-| The pattern for a default generated quadruple-precision NaN.  The `high' and
-| `low' values hold the most- and least-significant bits, respectively.
+| The pattern for a default generated quadruple-precision NaN.
 *----------------------------------------------------------------------------*/
-#if SNAN_BIT_IS_ONE
-#define float128_default_nan_high LIT64(0x7FFF7FFFFFFFFFFF)
-#define float128_default_nan_low  LIT64(0xFFFFFFFFFFFFFFFF)
-#elif defined(TARGET_S390X)
-#define float128_default_nan_high LIT64( 0x7FFF800000000000 )
-#define float128_default_nan_low  LIT64( 0x0000000000000000 )
+float128 float128_default_nan(float_status *status)
+{
+    float128 r;
+
+    if (status->snan_bit_is_one) {
+        r.low = LIT64(0xFFFFFFFFFFFFFFFF);
+        r.high = LIT64(0x7FFF7FFFFFFFFFFF);
+    } else {
+        r.low = LIT64(0x0000000000000000);
+#if defined(TARGET_S390X)
+        r.high = LIT64(0x7FFF800000000000);
 #else
-#define float128_default_nan_high LIT64( 0xFFFF800000000000 )
-#define float128_default_nan_low  LIT64( 0x0000000000000000 )
+        r.high = LIT64(0xFFFF800000000000);
 #endif
-
-const float128 float128_default_nan
-    = make_float128_init(float128_default_nan_high, float128_default_nan_low);
+    }
+    return r;
+}
 
 /*----------------------------------------------------------------------------
 | Raises the exceptions specified by `flags'.  Floating-point traps can be
@@ -188,12 +199,12 @@ typedef struct {
 } commonNaNT;
 
 #ifdef NO_SIGNALING_NANS
-int float16_is_quiet_nan(float16 a_)
+int float16_is_quiet_nan(float16 a_, float_status *status)
 {
     return float16_is_any_nan(a_);
 }
 
-int float16_is_signaling_nan(float16 a_)
+int float16_is_signaling_nan(float16 a_, float_status *status)
 {
     return 0;
 }
@@ -203,14 +214,14 @@ int float16_is_signaling_nan(float16 a_)
 | NaN; otherwise returns 0.
 *----------------------------------------------------------------------------*/
 
-int float16_is_quiet_nan(float16 a_)
+int float16_is_quiet_nan(float16 a_, float_status *status)
 {
     uint16_t a = float16_val(a_);
-#if SNAN_BIT_IS_ONE
-    return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
-#else
-    return ((a & ~0x8000) >= 0x7c80);
-#endif
+    if (status->snan_bit_is_one) {
+        return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
+    } else {
+        return ((a & ~0x8000) >= 0x7C80);
+    }
 }
 
 /*----------------------------------------------------------------------------
@@ -218,14 +229,14 @@ int float16_is_quiet_nan(float16 a_)
 | NaN; otherwise returns 0.
 *----------------------------------------------------------------------------*/
 
-int float16_is_signaling_nan(float16 a_)
+int float16_is_signaling_nan(float16 a_, float_status *status)
 {
     uint16_t a = float16_val(a_);
-#if SNAN_BIT_IS_ONE
-    return ((a & ~0x8000) >= 0x7c80);
-#else
-    return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
-#endif
+    if (status->snan_bit_is_one) {
+        return ((a & ~0x8000) >= 0x7C80);
+    } else {
+        return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
+    }
 }
 #endif
 
@@ -233,20 +244,16 @@ int float16_is_signaling_nan(float16 a_)
 | Returns a quiet NaN if the half-precision floating point value `a' is a
 | signaling NaN; otherwise returns `a'.
 *----------------------------------------------------------------------------*/
-float16 float16_maybe_silence_nan(float16 a_)
+float16 float16_maybe_silence_nan(float16 a_, float_status *status)
 {
-    if (float16_is_signaling_nan(a_)) {
-#if SNAN_BIT_IS_ONE
-#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
-        return float16_default_nan;
-#  else
-#    error Rules for silencing a signaling NaN are target-specific
-#  endif
-#else
-        uint16_t a = float16_val(a_);
-        a |= (1 << 9);
-        return make_float16(a);
-#endif
+    if (float16_is_signaling_nan(a_, status)) {
+        if (status->snan_bit_is_one) {
+            return float16_default_nan(status);
+        } else {
+            uint16_t a = float16_val(a_);
+            a |= (1 << 9);
+            return make_float16(a);
+        }
     }
     return a_;
 }
@@ -261,7 +268,7 @@ static commonNaNT float16ToCommonNaN(float16 a, float_status *status)
 {
     commonNaNT z;
 
-    if (float16_is_signaling_nan(a)) {
+    if (float16_is_signaling_nan(a, status)) {
         float_raise(float_flag_invalid, status);
     }
     z.sign = float16_val(a) >> 15;
@@ -280,24 +287,24 @@ static float16 commonNaNToFloat16(commonNaNT a, float_status *status)
     uint16_t mantissa = a.high>>54;
 
     if (status->default_nan_mode) {
-        return float16_default_nan;
+        return float16_default_nan(status);
     }
 
     if (mantissa) {
         return make_float16(((((uint16_t) a.sign) << 15)
                              | (0x1F << 10) | mantissa));
     } else {
-        return float16_default_nan;
+        return float16_default_nan(status);
     }
 }
 
 #ifdef NO_SIGNALING_NANS
-int float32_is_quiet_nan(float32 a_)
+int float32_is_quiet_nan(float32 a_, float_status *status)
 {
     return float32_is_any_nan(a_);
 }
 
-int float32_is_signaling_nan(float32 a_)
+int float32_is_signaling_nan(float32 a_, float_status *status)
 {
     return 0;
 }
@@ -307,14 +314,14 @@ int float32_is_signaling_nan(float32 a_)
 | NaN; otherwise returns 0.
 *----------------------------------------------------------------------------*/
 
-int float32_is_quiet_nan( float32 a_ )
+int float32_is_quiet_nan(float32 a_, float_status *status)
 {
     uint32_t a = float32_val(a_);
-#if SNAN_BIT_IS_ONE
-    return (((a >> 22) & 0x1ff) == 0x1fe) && (a & 0x003fffff);
-#else
-    return ((uint32_t)(a << 1) >= 0xff800000);
-#endif
+    if (status->snan_bit_is_one) {
+        return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003FFFFF);
+    } else {
+        return ((uint32_t)(a << 1) >= 0xFF800000);
+    }
 }
 
 /*----------------------------------------------------------------------------
@@ -322,14 +329,14 @@ int float32_is_quiet_nan( float32 a_ )
 | NaN; otherwise returns 0.
 *----------------------------------------------------------------------------*/
 
-int float32_is_signaling_nan( float32 a_ )
+int float32_is_signaling_nan(float32 a_, float_status *status)
 {
     uint32_t a = float32_val(a_);
-#if SNAN_BIT_IS_ONE
-    return ((uint32_t)(a << 1) >= 0xff800000);
-#else
-    return ( ( ( a>>22 ) & 0x1FF ) == 0x1FE ) && ( a & 0x003FFFFF );
-#endif
+    if (status->snan_bit_is_one) {
+        return ((uint32_t)(a << 1) >= 0xFF800000);
+    } else {
+        return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003FFFFF);
+    }
 }
 #endif
 
@@ -338,20 +345,16 @@ int float32_is_signaling_nan( float32 a_ )
 | signaling NaN; otherwise returns `a'.
 *----------------------------------------------------------------------------*/
 
-float32 float32_maybe_silence_nan( float32 a_ )
+float32 float32_maybe_silence_nan(float32 a_, float_status *status)
 {
-    if (float32_is_signaling_nan(a_)) {
-#if SNAN_BIT_IS_ONE
-#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
-        return float32_default_nan;
-#  else
-#    error Rules for silencing a signaling NaN are target-specific
-#  endif
-#else
-        uint32_t a = float32_val(a_);
-        a |= (1 << 22);
-        return make_float32(a);
-#endif
+    if (float32_is_signaling_nan(a_, status)) {
+        if (status->snan_bit_is_one) {
+            return float32_default_nan(status);
+        } else {
+            uint32_t a = float32_val(a_);
+            a |= (1 << 22);
+            return make_float32(a);
+        }
     }
     return a_;
 }
@@ -366,7 +369,7 @@ static commonNaNT float32ToCommonNaN(float32 a, float_status *status)
 {
     commonNaNT z;
 
-    if (float32_is_signaling_nan(a)) {
+    if (float32_is_signaling_nan(a, status)) {
         float_raise(float_flag_invalid, status);
     }
     z.sign = float32_val(a)>>31;
@@ -385,14 +388,15 @@ static float32 commonNaNToFloat32(commonNaNT a, float_status *status)
     uint32_t mantissa = a.high>>41;
 
     if (status->default_nan_mode) {
-        return float32_default_nan;
+        return float32_default_nan(status);
     }
 
-    if ( mantissa )
+    if (mantissa) {
         return make_float32(
             ( ( (uint32_t) a.sign )<<31 ) | 0x7F800000 | ( a.high>>41 ) );
-    else
-        return float32_default_nan;
+    } else {
+        return float32_default_nan(status);
+    }
 }
 
 /*----------------------------------------------------------------------------
@@ -626,10 +630,10 @@ static float32 propagateFloat32NaN(float32 a, float32 b, float_status *status)
     flag aIsLargerSignificand;
     uint32_t av, bv;
 
-    aIsQuietNaN = float32_is_quiet_nan( a );
-    aIsSignalingNaN = float32_is_signaling_nan( a );
-    bIsQuietNaN = float32_is_quiet_nan( b );
-    bIsSignalingNaN = float32_is_signaling_nan( b );
+    aIsQuietNaN = float32_is_quiet_nan(a, status);
+    aIsSignalingNaN = float32_is_signaling_nan(a, status);
+    bIsQuietNaN = float32_is_quiet_nan(b, status);
+    bIsSignalingNaN = float32_is_signaling_nan(b, status);
     av = float32_val(a);
     bv = float32_val(b);
 
@@ -637,8 +641,9 @@ static float32 propagateFloat32NaN(float32 a, float32 b, float_status *status)
         float_raise(float_flag_invalid, status);
     }
 
-    if (status->default_nan_mode)
-        return float32_default_nan;
+    if (status->default_nan_mode) {
+        return float32_default_nan(status);
+    }
 
     if ((uint32_t)(av<<1) < (uint32_t)(bv<<1)) {
         aIsLargerSignificand = 0;
@@ -650,9 +655,9 @@ static float32 propagateFloat32NaN(float32 a, float32 b, float_status *status)
 
     if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
                 aIsLargerSignificand)) {
-        return float32_maybe_silence_nan(b);
+        return float32_maybe_silence_nan(b, status);
     } else {
-        return float32_maybe_silence_nan(a);
+        return float32_maybe_silence_nan(a, status);
     }
 }
 
@@ -673,12 +678,12 @@ static float32 propagateFloat32MulAddNaN(float32 a, float32 b,
         cIsQuietNaN, cIsSignalingNaN;
     int which;
 
-    aIsQuietNaN = float32_is_quiet_nan(a);
-    aIsSignalingNaN = float32_is_signaling_nan(a);
-    bIsQuietNaN = float32_is_quiet_nan(b);
-    bIsSignalingNaN = float32_is_signaling_nan(b);
-    cIsQuietNaN = float32_is_quiet_nan(c);
-    cIsSignalingNaN = float32_is_signaling_nan(c);
+    aIsQuietNaN = float32_is_quiet_nan(a, status);
+    aIsSignalingNaN = float32_is_signaling_nan(a, status);
+    bIsQuietNaN = float32_is_quiet_nan(b, status);
+    bIsSignalingNaN = float32_is_signaling_nan(b, status);
+    cIsQuietNaN = float32_is_quiet_nan(c, status);
+    cIsSignalingNaN = float32_is_signaling_nan(c, status);
 
     if (aIsSignalingNaN | bIsSignalingNaN | cIsSignalingNaN) {
         float_raise(float_flag_invalid, status);
@@ -692,29 +697,29 @@ static float32 propagateFloat32MulAddNaN(float32 a, float32 b,
         /* Note that this check is after pickNaNMulAdd so that function
          * has an opportunity to set the Invalid flag.
          */
-        return float32_default_nan;
+        return float32_default_nan(status);
     }
 
     switch (which) {
     case 0:
-        return float32_maybe_silence_nan(a);
+        return float32_maybe_silence_nan(a, status);
     case 1:
-        return float32_maybe_silence_nan(b);
+        return float32_maybe_silence_nan(b, status);
     case 2:
-        return float32_maybe_silence_nan(c);
+        return float32_maybe_silence_nan(c, status);
     case 3:
     default:
-        return float32_default_nan;
+        return float32_default_nan(status);
     }
 }
 
 #ifdef NO_SIGNALING_NANS
-int float64_is_quiet_nan(float64 a_)
+int float64_is_quiet_nan(float64 a_, float_status *status)
 {
     return float64_is_any_nan(a_);
 }
 
-int float64_is_signaling_nan(float64 a_)
+int float64_is_signaling_nan(float64 a_, float_status *status)
 {
     return 0;
 }
@@ -724,15 +729,15 @@ int float64_is_signaling_nan(float64 a_)
 | NaN; otherwise returns 0.
 *----------------------------------------------------------------------------*/
 
-int float64_is_quiet_nan( float64 a_ )
+int float64_is_quiet_nan(float64 a_, float_status *status)
 {
     uint64_t a = float64_val(a_);
-#if SNAN_BIT_IS_ONE
-    return (((a >> 51) & 0xfff) == 0xffe)
-           && (a & 0x0007ffffffffffffULL);
-#else
-    return ((a << 1) >= 0xfff0000000000000ULL);
-#endif
+    if (status->snan_bit_is_one) {
+        return (((a >> 51) & 0xFFF) == 0xFFE)
+            && (a & 0x0007FFFFFFFFFFFFULL);
+    } else {
+        return ((a << 1) >= 0xFFF0000000000000ULL);
+    }
 }
 
 /*----------------------------------------------------------------------------
@@ -740,16 +745,15 @@ int float64_is_quiet_nan( float64 a_ )
 | NaN; otherwise returns 0.
 *----------------------------------------------------------------------------*/
 
-int float64_is_signaling_nan( float64 a_ )
+int float64_is_signaling_nan(float64 a_, float_status *status)
 {
     uint64_t a = float64_val(a_);
-#if SNAN_BIT_IS_ONE
-    return ((a << 1) >= 0xfff0000000000000ULL);
-#else
-    return
-           ( ( ( a>>51 ) & 0xFFF ) == 0xFFE )
-        && ( a & LIT64( 0x0007FFFFFFFFFFFF ) );
-#endif
+    if (status->snan_bit_is_one) {
+        return ((a << 1) >= 0xFFF0000000000000ULL);
+    } else {
+        return (((a >> 51) & 0xFFF) == 0xFFE)
+            && (a & LIT64(0x0007FFFFFFFFFFFF));
+    }
 }
 #endif
 
@@ -758,20 +762,16 @@ int float64_is_signaling_nan( float64 a_ )
 | signaling NaN; otherwise returns `a'.
 *----------------------------------------------------------------------------*/
 
-float64 float64_maybe_silence_nan( float64 a_ )
+float64 float64_maybe_silence_nan(float64 a_, float_status *status)
 {
-    if (float64_is_signaling_nan(a_)) {
-#if SNAN_BIT_IS_ONE
-#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
-        return float64_default_nan;
-#  else
-#    error Rules for silencing a signaling NaN are target-specific
-#  endif
-#else
-        uint64_t a = float64_val(a_);
-        a |= LIT64( 0x0008000000000000 );
-        return make_float64(a);
-#endif
+    if (float64_is_signaling_nan(a_, status)) {
+        if (status->snan_bit_is_one) {
+            return float64_default_nan(status);
+        } else {
+            uint64_t a = float64_val(a_);
+            a |= LIT64(0x0008000000000000);
+            return make_float64(a);
+        }
     }
     return a_;
 }
@@ -786,7 +786,7 @@ static commonNaNT float64ToCommonNaN(float64 a, float_status *status)
 {
     commonNaNT z;
 
-    if (float64_is_signaling_nan(a)) {
+    if (float64_is_signaling_nan(a, status)) {
         float_raise(float_flag_invalid, status);
     }
     z.sign = float64_val(a)>>63;
@@ -805,16 +805,17 @@ static float64 commonNaNToFloat64(commonNaNT a, float_status *status)
     uint64_t mantissa = a.high>>12;
 
     if (status->default_nan_mode) {
-        return float64_default_nan;
+        return float64_default_nan(status);
     }
 
-    if ( mantissa )
+    if (mantissa) {
         return make_float64(
               ( ( (uint64_t) a.sign )<<63 )
             | LIT64( 0x7FF0000000000000 )
             | ( a.high>>12 ));
-    else
-        return float64_default_nan;
+    } else {
+        return float64_default_nan(status);
+    }
 }
 
 /*----------------------------------------------------------------------------
@@ -829,10 +830,10 @@ static float64 propagateFloat64NaN(float64 a, float64 b, float_status *status)
     flag aIsLargerSignificand;
     uint64_t av, bv;
 
-    aIsQuietNaN = float64_is_quiet_nan( a );
-    aIsSignalingNaN = float64_is_signaling_nan( a );
-    bIsQuietNaN = float64_is_quiet_nan( b );
-    bIsSignalingNaN = float64_is_signaling_nan( b );
+    aIsQuietNaN = float64_is_quiet_nan(a, status);
+    aIsSignalingNaN = float64_is_signaling_nan(a, status);
+    bIsQuietNaN = float64_is_quiet_nan(b, status);
+    bIsSignalingNaN = float64_is_signaling_nan(b, status);
     av = float64_val(a);
     bv = float64_val(b);
 
@@ -840,8 +841,9 @@ static float64 propagateFloat64NaN(float64 a, float64 b, float_status *status)
         float_raise(float_flag_invalid, status);
     }
 
-    if (status->default_nan_mode)
-        return float64_default_nan;
+    if (status->default_nan_mode) {
+        return float64_default_nan(status);
+    }
 
     if ((uint64_t)(av<<1) < (uint64_t)(bv<<1)) {
         aIsLargerSignificand = 0;
@@ -853,9 +855,9 @@ static float64 propagateFloat64NaN(float64 a, float64 b, float_status *status)
 
     if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
                 aIsLargerSignificand)) {
-        return float64_maybe_silence_nan(b);
+        return float64_maybe_silence_nan(b, status);
     } else {
-        return float64_maybe_silence_nan(a);
+        return float64_maybe_silence_nan(a, status);
     }
 }
 
@@ -876,12 +878,12 @@ static float64 propagateFloat64MulAddNaN(float64 a, float64 b,
         cIsQuietNaN, cIsSignalingNaN;
     int which;
 
-    aIsQuietNaN = float64_is_quiet_nan(a);
-    aIsSignalingNaN = float64_is_signaling_nan(a);
-    bIsQuietNaN = float64_is_quiet_nan(b);
-    bIsSignalingNaN = float64_is_signaling_nan(b);
-    cIsQuietNaN = float64_is_quiet_nan(c);
-    cIsSignalingNaN = float64_is_signaling_nan(c);
+    aIsQuietNaN = float64_is_quiet_nan(a, status);
+    aIsSignalingNaN = float64_is_signaling_nan(a, status);
+    bIsQuietNaN = float64_is_quiet_nan(b, status);
+    bIsSignalingNaN = float64_is_signaling_nan(b, status);
+    cIsQuietNaN = float64_is_quiet_nan(c, status);
+    cIsSignalingNaN = float64_is_signaling_nan(c, status);
 
     if (aIsSignalingNaN | bIsSignalingNaN | cIsSignalingNaN) {
         float_raise(float_flag_invalid, status);
@@ -895,29 +897,29 @@ static float64 propagateFloat64MulAddNaN(float64 a, float64 b,
         /* Note that this check is after pickNaNMulAdd so that function
          * has an opportunity to set the Invalid flag.
          */
-        return float64_default_nan;
+        return float64_default_nan(status);
     }
 
     switch (which) {
     case 0:
-        return float64_maybe_silence_nan(a);
+        return float64_maybe_silence_nan(a, status);
     case 1:
-        return float64_maybe_silence_nan(b);
+        return float64_maybe_silence_nan(b, status);
     case 2:
-        return float64_maybe_silence_nan(c);
+        return float64_maybe_silence_nan(c, status);
     case 3:
     default:
-        return float64_default_nan;
+        return float64_default_nan(status);
     }
 }
 
 #ifdef NO_SIGNALING_NANS
-int floatx80_is_quiet_nan(floatx80 a_)
+int floatx80_is_quiet_nan(floatx80 a_, float_status *status)
 {
     return floatx80_is_any_nan(a_);
 }
 
-int floatx80_is_signaling_nan(floatx80 a_)
+int floatx80_is_signaling_nan(floatx80 a_, float_status *status)
 {
     return 0;
 }
@@ -928,19 +930,19 @@ int floatx80_is_signaling_nan(floatx80 a_)
 | function for other types as floatx80 has an explicit bit.
 *----------------------------------------------------------------------------*/
 
-int floatx80_is_quiet_nan( floatx80 a )
+int floatx80_is_quiet_nan(floatx80 a, float_status *status)
 {
-#if SNAN_BIT_IS_ONE
-    uint64_t aLow;
+    if (status->snan_bit_is_one) {
+        uint64_t aLow;
 
-    aLow = a.low & ~0x4000000000000000ULL;
-    return ((a.high & 0x7fff) == 0x7fff)
-        && (aLow << 1)
-        && (a.low == aLow);
-#else
-    return ( ( a.high & 0x7FFF ) == 0x7FFF )
-        && (LIT64( 0x8000000000000000 ) <= ((uint64_t) ( a.low<<1 )));
-#endif
+        aLow = a.low & ~0x4000000000000000ULL;
+        return ((a.high & 0x7FFF) == 0x7FFF)
+            && (aLow << 1)
+            && (a.low == aLow);
+    } else {
+        return ((a.high & 0x7FFF) == 0x7FFF)
+            && (LIT64(0x8000000000000000) <= ((uint64_t)(a.low << 1)));
+    }
 }
 
 /*----------------------------------------------------------------------------
@@ -949,20 +951,19 @@ int floatx80_is_quiet_nan( floatx80 a )
 | function for other types as floatx80 has an explicit bit.
 *----------------------------------------------------------------------------*/
 
-int floatx80_is_signaling_nan( floatx80 a )
+int floatx80_is_signaling_nan(floatx80 a, float_status *status)
 {
-#if SNAN_BIT_IS_ONE
-    return ((a.high & 0x7fff) == 0x7fff)
-        && ((a.low << 1) >= 0x8000000000000000ULL);
-#else
-    uint64_t aLow;
+    if (status->snan_bit_is_one) {
+        return ((a.high & 0x7FFF) == 0x7FFF)
+            && ((a.low << 1) >= 0x8000000000000000ULL);
+    } else {
+        uint64_t aLow;
 
-    aLow = a.low & ~ LIT64( 0x4000000000000000 );
-    return
-           ( ( a.high & 0x7FFF ) == 0x7FFF )
-        && (uint64_t) ( aLow<<1 )
-        && ( a.low == aLow );
-#endif
+        aLow = a.low & ~LIT64(0x4000000000000000);
+        return ((a.high & 0x7FFF) == 0x7FFF)
+            && (uint64_t)(aLow << 1)
+            && (a.low == aLow);
+    }
 }
 #endif
 
@@ -971,20 +972,15 @@ int floatx80_is_signaling_nan( floatx80 a )
 | `a' is a signaling NaN; otherwise returns `a'.
 *----------------------------------------------------------------------------*/
 
-floatx80 floatx80_maybe_silence_nan( floatx80 a )
+floatx80 floatx80_maybe_silence_nan(floatx80 a, float_status *status)
 {
-    if (floatx80_is_signaling_nan(a)) {
-#if SNAN_BIT_IS_ONE
-#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
-        a.low = floatx80_default_nan_low;
-        a.high = floatx80_default_nan_high;
-#  else
-#    error Rules for silencing a signaling NaN are target-specific
-#  endif
-#else
-        a.low |= LIT64( 0xC000000000000000 );
-        return a;
-#endif
+    if (floatx80_is_signaling_nan(a, status)) {
+        if (status->snan_bit_is_one) {
+            a = floatx80_default_nan(status);
+        } else {
+            a.low |= LIT64(0xC000000000000000);
+            return a;
+        }
     }
     return a;
 }
@@ -997,9 +993,10 @@ floatx80 floatx80_maybe_silence_nan( floatx80 a )
 
 static commonNaNT floatx80ToCommonNaN(floatx80 a, float_status *status)
 {
+    floatx80 dflt;
     commonNaNT z;
 
-    if (floatx80_is_signaling_nan(a)) {
+    if (floatx80_is_signaling_nan(a, status)) {
         float_raise(float_flag_invalid, status);
     }
     if ( a.low >> 63 ) {
@@ -1007,9 +1004,10 @@ static commonNaNT floatx80ToCommonNaN(floatx80 a, float_status *status)
         z.low = 0;
         z.high = a.low << 1;
     } else {
-        z.sign = floatx80_default_nan_high >> 15;
+        dflt = floatx80_default_nan(status);
+        z.sign = dflt.high >> 15;
         z.low = 0;
-        z.high = floatx80_default_nan_low << 1;
+        z.high = dflt.low << 1;
     }
     return z;
 }
@@ -1024,19 +1022,15 @@ static floatx80 commonNaNToFloatx80(commonNaNT a, float_status *status)
     floatx80 z;
 
     if (status->default_nan_mode) {
-        z.low = floatx80_default_nan_low;
-        z.high = floatx80_default_nan_high;
-        return z;
+        return floatx80_default_nan(status);
     }
 
     if (a.high >> 1) {
         z.low = LIT64( 0x8000000000000000 ) | a.high >> 1;
         z.high = ( ( (uint16_t) a.sign )<<15 ) | 0x7FFF;
     } else {
-        z.low = floatx80_default_nan_low;
-        z.high = floatx80_default_nan_high;
+        z = floatx80_default_nan(status);
     }
-
     return z;
 }
 
@@ -1052,19 +1046,17 @@ static floatx80 propagateFloatx80NaN(floatx80 a, floatx80 b,
     flag aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN;
     flag aIsLargerSignificand;
 
-    aIsQuietNaN = floatx80_is_quiet_nan( a );
-    aIsSignalingNaN = floatx80_is_signaling_nan( a );
-    bIsQuietNaN = floatx80_is_quiet_nan( b );
-    bIsSignalingNaN = floatx80_is_signaling_nan( b );
+    aIsQuietNaN = floatx80_is_quiet_nan(a, status);
+    aIsSignalingNaN = floatx80_is_signaling_nan(a, status);
+    bIsQuietNaN = floatx80_is_quiet_nan(b, status);
+    bIsSignalingNaN = floatx80_is_signaling_nan(b, status);
 
     if (aIsSignalingNaN | bIsSignalingNaN) {
         float_raise(float_flag_invalid, status);
     }
 
     if (status->default_nan_mode) {
-        a.low = floatx80_default_nan_low;
-        a.high = floatx80_default_nan_high;
-        return a;
+        return floatx80_default_nan(status);
     }
 
     if (a.low < b.low) {
@@ -1077,19 +1069,19 @@ static floatx80 propagateFloatx80NaN(floatx80 a, floatx80 b,
 
     if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
                 aIsLargerSignificand)) {
-        return floatx80_maybe_silence_nan(b);
+        return floatx80_maybe_silence_nan(b, status);
     } else {
-        return floatx80_maybe_silence_nan(a);
+        return floatx80_maybe_silence_nan(a, status);
     }
 }
 
 #ifdef NO_SIGNALING_NANS
-int float128_is_quiet_nan(float128 a_)
+int float128_is_quiet_nan(float128 a_, float_status *status)
 {
     return float128_is_any_nan(a_);
 }
 
-int float128_is_signaling_nan(float128 a_)
+int float128_is_signaling_nan(float128 a_, float_status *status)
 {
     return 0;
 }
@@ -1099,16 +1091,15 @@ int float128_is_signaling_nan(float128 a_)
 | NaN; otherwise returns 0.
 *----------------------------------------------------------------------------*/
 
-int float128_is_quiet_nan( float128 a )
+int float128_is_quiet_nan(float128 a, float_status *status)
 {
-#if SNAN_BIT_IS_ONE
-    return (((a.high >> 47) & 0xffff) == 0xfffe)
-        && (a.low || (a.high & 0x00007fffffffffffULL));
-#else
-    return
-        ((a.high << 1) >= 0xffff000000000000ULL)
-        && (a.low || (a.high & 0x0000ffffffffffffULL));
-#endif
+    if (status->snan_bit_is_one) {
+        return (((a.high >> 47) & 0xFFFF) == 0xFFFE)
+            && (a.low || (a.high & 0x00007FFFFFFFFFFFULL));
+    } else {
+        return ((a.high << 1) >= 0xFFFF000000000000ULL)
+            && (a.low || (a.high & 0x0000FFFFFFFFFFFFULL));
+    }
 }
 
 /*----------------------------------------------------------------------------
@@ -1116,17 +1107,15 @@ int float128_is_quiet_nan( float128 a )
 | signaling NaN; otherwise returns 0.
 *----------------------------------------------------------------------------*/
 
-int float128_is_signaling_nan( float128 a )
+int float128_is_signaling_nan(float128 a, float_status *status)
 {
-#if SNAN_BIT_IS_ONE
-    return
-        ((a.high << 1) >= 0xffff000000000000ULL)
-        && (a.low || (a.high & 0x0000ffffffffffffULL));
-#else
-    return
-           ( ( ( a.high>>47 ) & 0xFFFF ) == 0xFFFE )
-        && ( a.low || ( a.high & LIT64( 0x00007FFFFFFFFFFF ) ) );
-#endif
+    if (status->snan_bit_is_one) {
+        return ((a.high << 1) >= 0xFFFF000000000000ULL)
+            && (a.low || (a.high & 0x0000FFFFFFFFFFFFULL));
+    } else {
+        return (((a.high >> 47) & 0xFFFF) == 0xFFFE)
+            && (a.low || (a.high & LIT64(0x00007FFFFFFFFFFF)));
+    }
 }
 #endif
 
@@ -1135,20 +1124,15 @@ int float128_is_signaling_nan( float128 a )
 | a signaling NaN; otherwise returns `a'.
 *----------------------------------------------------------------------------*/
 
-float128 float128_maybe_silence_nan( float128 a )
+float128 float128_maybe_silence_nan(float128 a, float_status *status)
 {
-    if (float128_is_signaling_nan(a)) {
-#if SNAN_BIT_IS_ONE
-#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
-        a.low = float128_default_nan_low;
-        a.high = float128_default_nan_high;
-#  else
-#    error Rules for silencing a signaling NaN are target-specific
-#  endif
-#else
-        a.high |= LIT64( 0x0000800000000000 );
-        return a;
-#endif
+    if (float128_is_signaling_nan(a, status)) {
+        if (status->snan_bit_is_one) {
+            a = float128_default_nan(status);
+        } else {
+            a.high |= LIT64(0x0000800000000000);
+            return a;
+        }
     }
     return a;
 }
@@ -1163,7 +1147,7 @@ static commonNaNT float128ToCommonNaN(float128 a, float_status *status)
 {
     commonNaNT z;
 
-    if (float128_is_signaling_nan(a)) {
+    if (float128_is_signaling_nan(a, status)) {
         float_raise(float_flag_invalid, status);
     }
     z.sign = a.high>>63;
@@ -1181,9 +1165,7 @@ static float128 commonNaNToFloat128(commonNaNT a, float_status *status)
     float128 z;
 
     if (status->default_nan_mode) {
-        z.low = float128_default_nan_low;
-        z.high = float128_default_nan_high;
-        return z;
+        return float128_default_nan(status);
     }
 
     shift128Right( a.high, a.low, 16, &z.high, &z.low );
@@ -1203,19 +1185,17 @@ static float128 propagateFloat128NaN(float128 a, float128 b,
     flag aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN;
     flag aIsLargerSignificand;
 
-    aIsQuietNaN = float128_is_quiet_nan( a );
-    aIsSignalingNaN = float128_is_signaling_nan( a );
-    bIsQuietNaN = float128_is_quiet_nan( b );
-    bIsSignalingNaN = float128_is_signaling_nan( b );
+    aIsQuietNaN = float128_is_quiet_nan(a, status);
+    aIsSignalingNaN = float128_is_signaling_nan(a, status);
+    bIsQuietNaN = float128_is_quiet_nan(b, status);
+    bIsSignalingNaN = float128_is_signaling_nan(b, status);
 
     if (aIsSignalingNaN | bIsSignalingNaN) {
         float_raise(float_flag_invalid, status);
     }
 
     if (status->default_nan_mode) {
-        a.low = float128_default_nan_low;
-        a.high = float128_default_nan_high;
-        return a;
+        return float128_default_nan(status);
     }
 
     if (lt128(a.high<<1, a.low, b.high<<1, b.low)) {
@@ -1228,9 +1208,8 @@ static float128 propagateFloat128NaN(float128 a, float128 b,
 
     if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
                 aIsLargerSignificand)) {
-        return float128_maybe_silence_nan(b);
+        return float128_maybe_silence_nan(b, status);
     } else {
-        return float128_maybe_silence_nan(a);
+        return float128_maybe_silence_nan(a, status);
     }
 }
-