diff mbox series

[01/21] softfloat: make NO_SIGNALING_NANS runtime property

Message ID 20200706234737.32378-2-jcmvbkbc@gmail.com (mailing list archive)
State New, archived
Headers show
Series target/xtensa: implement double precision FPU | expand

Commit Message

Max Filippov July 6, 2020, 11:47 p.m. UTC 
target/xtensa, the only user of NO_SIGNALING_NANS macro has FPU
implementations with and without the corresponding property. With
NO_SIGNALING_NANS being a macro they cannot be a part of the same QEMU
executable.
Replace macro with new property in float_status to allow cores with
different FPU implementations coexist.

Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: "Alex Bennée" <alex.bennee@linaro.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 fpu/softfloat-specialize.inc.c  | 228 ++++++++++++++++----------------
 include/fpu/softfloat-helpers.h |   5 +
 include/fpu/softfloat-types.h   |   1 +
 3 files changed, 117 insertions(+), 117 deletions(-)

Comments

Alex Bennée July 7, 2020, 10:28 a.m. UTC | #1 
Max Filippov <jcmvbkbc@gmail.com> writes:

> target/xtensa, the only user of NO_SIGNALING_NANS macro has FPU
> implementations with and without the corresponding property. With
> NO_SIGNALING_NANS being a macro they cannot be a part of the same QEMU
> executable.
> Replace macro with new property in float_status to allow cores with
> different FPU implementations coexist.
>
> Cc: Peter Maydell <peter.maydell@linaro.org>
> Cc: "Alex Bennée" <alex.bennee@linaro.org>
> Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
> ---
>  fpu/softfloat-specialize.inc.c  | 228 ++++++++++++++++----------------
>  include/fpu/softfloat-helpers.h |   5 +
>  include/fpu/softfloat-types.h   |   1 +
>  3 files changed, 117 insertions(+), 117 deletions(-)
>
> diff --git a/fpu/softfloat-specialize.inc.c b/fpu/softfloat-specialize.inc.c
> index 44f5b661f831..b26bc039b0b6 100644
> --- a/fpu/softfloat-specialize.inc.c
> +++ b/fpu/softfloat-specialize.inc.c
> @@ -79,13 +79,6 @@ this code that are retained.
>   * version 2 or later. See the COPYING file in the top-level directory.
>   */
>  
> -/* Define for architectures which deviate from IEEE in not supporting
> - * signaling NaNs (so all NaNs are treated as quiet).
> - */
> -#if defined(TARGET_XTENSA)
> -#define NO_SIGNALING_NANS 1
> -#endif
> -
>  /* Define how the architecture discriminates signaling NaNs.
>   * This done with the most significant bit of the fraction.
>   * In IEEE 754-1985 this was implementation defined, but in IEEE 754-2008
> @@ -111,12 +104,12 @@ static inline bool snan_bit_is_one(float_status *status)
>  
>  static bool parts_is_snan_frac(uint64_t frac, float_status *status)
>  {
> -#ifdef NO_SIGNALING_NANS
> -    return false;
> -#else
> -    bool msb = extract64(frac, DECOMPOSED_BINARY_POINT - 1, 1);
> -    return msb == snan_bit_is_one(status);
> -#endif
> +    if (status->no_signaling_nans) {
> +        return false;

I have no objection in principle but seeing as we go to the trouble of
allowing snan_bit_is_one() to constant fold away I think it would be
worth doing the same with a no_signalling_nans(status). We can then
avoid an admittedly well predicted test for the non XTENSA case.

> +    } else {
> +        bool msb = extract64(frac, DECOMPOSED_BINARY_POINT - 1, 1);
> +        return msb == snan_bit_is_one(status);
> +    }
>  }
>  
>  /*----------------------------------------------------------------------------
> @@ -170,9 +163,10 @@ static FloatParts parts_default_nan(float_status *status)
>  
>  static FloatParts parts_silence_nan(FloatParts a, float_status *status)
>  {
> -#ifdef NO_SIGNALING_NANS
> -    g_assert_not_reached();

We could then keep the assert:

  g_assert(!no_signaling_nan(status))

<snip>
>      return status->tininess_before_rounding;
> diff --git a/include/fpu/softfloat-types.h b/include/fpu/softfloat-types.h
> index 7680193ebc1c..10bd208e559f 100644
> --- a/include/fpu/softfloat-types.h
> +++ b/include/fpu/softfloat-types.h
> @@ -167,6 +167,7 @@ typedef struct float_status {
>      bool default_nan_mode;
>      /* not always used -- see snan_bit_is_one() in
>      softfloat-specialize.h */

and then expand this comment:

    /* the flags bellow are not used on all specializations and may
     * constant fold away (see snan_bit_is_one()/no_signalling_nans() in
     * softfloat-specialize.h)
     */

>      bool snan_bit_is_one;
> +    bool no_signaling_nans;
>  } float_status;
>  
>  #endif /* SOFTFLOAT_TYPES_H */
Philippe Mathieu-Daudé July 8, 2020, 5:41 p.m. UTC | #2 
On 7/7/20 1:47 AM, Max Filippov wrote:
> target/xtensa, the only user of NO_SIGNALING_NANS macro has FPU
> implementations with and without the corresponding property. With
> NO_SIGNALING_NANS being a macro they cannot be a part of the same QEMU
> executable.
> Replace macro with new property in float_status to allow cores with
> different FPU implementations coexist.
> 
> Cc: Peter Maydell <peter.maydell@linaro.org>
> Cc: "Alex Bennée" <alex.bennee@linaro.org>
> Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
> ---
>  fpu/softfloat-specialize.inc.c  | 228 ++++++++++++++++----------------
>  include/fpu/softfloat-helpers.h |   5 +
>  include/fpu/softfloat-types.h   |   1 +
>  3 files changed, 117 insertions(+), 117 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
diff mbox series

Patch

diff --git a/fpu/softfloat-specialize.inc.c b/fpu/softfloat-specialize.inc.c
index 44f5b661f831..b26bc039b0b6 100644
--- a/fpu/softfloat-specialize.inc.c
+++ b/fpu/softfloat-specialize.inc.c
@@ -79,13 +79,6 @@  this code that are retained.
  * version 2 or later. See the COPYING file in the top-level directory.
  */
 
-/* Define for architectures which deviate from IEEE in not supporting
- * signaling NaNs (so all NaNs are treated as quiet).
- */
-#if defined(TARGET_XTENSA)
-#define NO_SIGNALING_NANS 1
-#endif
-
 /* Define how the architecture discriminates signaling NaNs.
  * This done with the most significant bit of the fraction.
  * In IEEE 754-1985 this was implementation defined, but in IEEE 754-2008
@@ -111,12 +104,12 @@  static inline bool snan_bit_is_one(float_status *status)
 
 static bool parts_is_snan_frac(uint64_t frac, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return false;
-#else
-    bool msb = extract64(frac, DECOMPOSED_BINARY_POINT - 1, 1);
-    return msb == snan_bit_is_one(status);
-#endif
+    if (status->no_signaling_nans) {
+        return false;
+    } else {
+        bool msb = extract64(frac, DECOMPOSED_BINARY_POINT - 1, 1);
+        return msb == snan_bit_is_one(status);
+    }
 }
 
 /*----------------------------------------------------------------------------
@@ -170,9 +163,10 @@  static FloatParts parts_default_nan(float_status *status)
 
 static FloatParts parts_silence_nan(FloatParts a, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    g_assert_not_reached();
-#elif defined(TARGET_HPPA)
+    if (status->no_signaling_nans) {
+        g_assert_not_reached();
+    }
+#if defined(TARGET_HPPA)
     a.frac &= ~(1ULL << (DECOMPOSED_BINARY_POINT - 1));
     a.frac |= 1ULL << (DECOMPOSED_BINARY_POINT - 2);
 #else
@@ -247,16 +241,16 @@  typedef struct {
 
 bool float16_is_quiet_nan(float16 a_, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return float16_is_any_nan(a_);
-#else
-    uint16_t a = float16_val(a_);
-    if (snan_bit_is_one(status)) {
-        return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
+    if (status->no_signaling_nans) {
+        return float16_is_any_nan(a_);
     } else {
-        return ((a & ~0x8000) >= 0x7C80);
+        uint16_t a = float16_val(a_);
+        if (snan_bit_is_one(status)) {
+            return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
+        } else {
+            return ((a & ~0x8000) >= 0x7C80);
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -266,16 +260,16 @@  bool float16_is_quiet_nan(float16 a_, float_status *status)
 
 bool float16_is_signaling_nan(float16 a_, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return 0;
-#else
-    uint16_t a = float16_val(a_);
-    if (snan_bit_is_one(status)) {
-        return ((a & ~0x8000) >= 0x7C80);
+    if (status->no_signaling_nans) {
+        return 0;
     } else {
-        return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
+        uint16_t a = float16_val(a_);
+        if (snan_bit_is_one(status)) {
+            return ((a & ~0x8000) >= 0x7C80);
+        } else {
+            return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -285,16 +279,16 @@  bool float16_is_signaling_nan(float16 a_, float_status *status)
 
 bool float32_is_quiet_nan(float32 a_, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return float32_is_any_nan(a_);
-#else
-    uint32_t a = float32_val(a_);
-    if (snan_bit_is_one(status)) {
-        return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003FFFFF);
+    if (status->no_signaling_nans) {
+        return float32_is_any_nan(a_);
     } else {
-        return ((uint32_t)(a << 1) >= 0xFF800000);
+        uint32_t a = float32_val(a_);
+        if (snan_bit_is_one(status)) {
+            return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003FFFFF);
+        } else {
+            return ((uint32_t)(a << 1) >= 0xFF800000);
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -304,16 +298,16 @@  bool float32_is_quiet_nan(float32 a_, float_status *status)
 
 bool float32_is_signaling_nan(float32 a_, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return 0;
-#else
-    uint32_t a = float32_val(a_);
-    if (snan_bit_is_one(status)) {
-        return ((uint32_t)(a << 1) >= 0xFF800000);
+    if (status->no_signaling_nans) {
+        return 0;
     } else {
-        return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003FFFFF);
+        uint32_t a = float32_val(a_);
+        if (snan_bit_is_one(status)) {
+            return ((uint32_t)(a << 1) >= 0xFF800000);
+        } else {
+            return (((a >> 22) & 0x1FF) == 0x1FE) && (a & 0x003FFFFF);
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -639,17 +633,17 @@  static float32 propagateFloat32NaN(float32 a, float32 b, float_status *status)
 
 bool float64_is_quiet_nan(float64 a_, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return float64_is_any_nan(a_);
-#else
-    uint64_t a = float64_val(a_);
-    if (snan_bit_is_one(status)) {
-        return (((a >> 51) & 0xFFF) == 0xFFE)
-            && (a & 0x0007FFFFFFFFFFFFULL);
+    if (status->no_signaling_nans) {
+        return float64_is_any_nan(a_);
     } else {
-        return ((a << 1) >= 0xFFF0000000000000ULL);
+        uint64_t a = float64_val(a_);
+        if (snan_bit_is_one(status)) {
+            return (((a >> 51) & 0xFFF) == 0xFFE)
+                && (a & 0x0007FFFFFFFFFFFFULL);
+        } else {
+            return ((a << 1) >= 0xFFF0000000000000ULL);
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -659,17 +653,17 @@  bool float64_is_quiet_nan(float64 a_, float_status *status)
 
 bool float64_is_signaling_nan(float64 a_, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return 0;
-#else
-    uint64_t a = float64_val(a_);
-    if (snan_bit_is_one(status)) {
-        return ((a << 1) >= 0xFFF0000000000000ULL);
+    if (status->no_signaling_nans) {
+        return 0;
     } else {
-        return (((a >> 51) & 0xFFF) == 0xFFE)
-            && (a & UINT64_C(0x0007FFFFFFFFFFFF));
+        uint64_t a = float64_val(a_);
+        if (snan_bit_is_one(status)) {
+            return ((a << 1) >= 0xFFF0000000000000ULL);
+        } else {
+            return (((a >> 51) & 0xFFF) == 0xFFE)
+                && (a & UINT64_C(0x0007FFFFFFFFFFFF));
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -778,21 +772,21 @@  static float64 propagateFloat64NaN(float64 a, float64 b, float_status *status)
 
 int floatx80_is_quiet_nan(floatx80 a, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return floatx80_is_any_nan(a);
-#else
-    if (snan_bit_is_one(status)) {
-        uint64_t aLow;
-
-        aLow = a.low & ~0x4000000000000000ULL;
-        return ((a.high & 0x7FFF) == 0x7FFF)
-            && (aLow << 1)
-            && (a.low == aLow);
+    if (status->no_signaling_nans) {
+        return floatx80_is_any_nan(a);
     } else {
-        return ((a.high & 0x7FFF) == 0x7FFF)
-            && (UINT64_C(0x8000000000000000) <= ((uint64_t)(a.low << 1)));
+        if (snan_bit_is_one(status)) {
+            uint64_t aLow;
+
+            aLow = a.low & ~0x4000000000000000ULL;
+            return ((a.high & 0x7FFF) == 0x7FFF)
+                && (aLow << 1)
+                && (a.low == aLow);
+        } else {
+            return ((a.high & 0x7FFF) == 0x7FFF)
+                && (UINT64_C(0x8000000000000000) <= ((uint64_t)(a.low << 1)));
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -803,21 +797,21 @@  int floatx80_is_quiet_nan(floatx80 a, float_status *status)
 
 int floatx80_is_signaling_nan(floatx80 a, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return 0;
-#else
-    if (snan_bit_is_one(status)) {
-        return ((a.high & 0x7FFF) == 0x7FFF)
-            && ((a.low << 1) >= 0x8000000000000000ULL);
+    if (status->no_signaling_nans) {
+        return 0;
     } else {
-        uint64_t aLow;
+        if (snan_bit_is_one(status)) {
+            return ((a.high & 0x7FFF) == 0x7FFF)
+                && ((a.low << 1) >= 0x8000000000000000ULL);
+        } else {
+            uint64_t aLow;
 
-        aLow = a.low & ~UINT64_C(0x4000000000000000);
-        return ((a.high & 0x7FFF) == 0x7FFF)
-            && (uint64_t)(aLow << 1)
-            && (a.low == aLow);
+            aLow = a.low & ~UINT64_C(0x4000000000000000);
+            return ((a.high & 0x7FFF) == 0x7FFF)
+                && (uint64_t)(aLow << 1)
+                && (a.low == aLow);
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -941,17 +935,17 @@  floatx80 propagateFloatx80NaN(floatx80 a, floatx80 b, float_status *status)
 
 bool float128_is_quiet_nan(float128 a, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return float128_is_any_nan(a);
-#else
-    if (snan_bit_is_one(status)) {
-        return (((a.high >> 47) & 0xFFFF) == 0xFFFE)
-            && (a.low || (a.high & 0x00007FFFFFFFFFFFULL));
+    if (status->no_signaling_nans) {
+        return float128_is_any_nan(a);
     } else {
-        return ((a.high << 1) >= 0xFFFF000000000000ULL)
-            && (a.low || (a.high & 0x0000FFFFFFFFFFFFULL));
+        if (snan_bit_is_one(status)) {
+            return (((a.high >> 47) & 0xFFFF) == 0xFFFE)
+                && (a.low || (a.high & 0x00007FFFFFFFFFFFULL));
+        } else {
+            return ((a.high << 1) >= 0xFFFF000000000000ULL)
+                && (a.low || (a.high & 0x0000FFFFFFFFFFFFULL));
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -961,17 +955,17 @@  bool float128_is_quiet_nan(float128 a, float_status *status)
 
 bool float128_is_signaling_nan(float128 a, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    return 0;
-#else
-    if (snan_bit_is_one(status)) {
-        return ((a.high << 1) >= 0xFFFF000000000000ULL)
-            && (a.low || (a.high & 0x0000FFFFFFFFFFFFULL));
+    if (status->no_signaling_nans) {
+        return 0;
     } else {
-        return (((a.high >> 47) & 0xFFFF) == 0xFFFE)
-            && (a.low || (a.high & UINT64_C(0x00007FFFFFFFFFFF)));
+        if (snan_bit_is_one(status)) {
+            return ((a.high << 1) >= 0xFFFF000000000000ULL)
+                && (a.low || (a.high & 0x0000FFFFFFFFFFFFULL));
+        } else {
+            return (((a.high >> 47) & 0xFFFF) == 0xFFFE)
+                && (a.low || (a.high & UINT64_C(0x00007FFFFFFFFFFF)));
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
@@ -981,16 +975,16 @@  bool float128_is_signaling_nan(float128 a, float_status *status)
 
 float128 float128_silence_nan(float128 a, float_status *status)
 {
-#ifdef NO_SIGNALING_NANS
-    g_assert_not_reached();
-#else
-    if (snan_bit_is_one(status)) {
-        return float128_default_nan(status);
+    if (status->no_signaling_nans) {
+        g_assert_not_reached();
     } else {
-        a.high |= UINT64_C(0x0000800000000000);
-        return a;
+        if (snan_bit_is_one(status)) {
+            return float128_default_nan(status);
+        } else {
+            a.high |= UINT64_C(0x0000800000000000);
+            return a;
+        }
     }
-#endif
 }
 
 /*----------------------------------------------------------------------------
diff --git a/include/fpu/softfloat-helpers.h b/include/fpu/softfloat-helpers.h
index 735ed6b653ee..e842f83a1285 100644
--- a/include/fpu/softfloat-helpers.h
+++ b/include/fpu/softfloat-helpers.h
@@ -95,6 +95,11 @@  static inline void set_snan_bit_is_one(bool val, float_status *status)
     status->snan_bit_is_one = val;
 }
 
+static inline void set_no_signaling_nans(bool val, float_status *status)
+{
+    status->no_signaling_nans = val;
+}
+
 static inline bool get_float_detect_tininess(float_status *status)
 {
     return status->tininess_before_rounding;
diff --git a/include/fpu/softfloat-types.h b/include/fpu/softfloat-types.h
index 7680193ebc1c..10bd208e559f 100644
--- a/include/fpu/softfloat-types.h
+++ b/include/fpu/softfloat-types.h
@@ -167,6 +167,7 @@  typedef struct float_status {
     bool default_nan_mode;
     /* not always used -- see snan_bit_is_one() in softfloat-specialize.h */
     bool snan_bit_is_one;
+    bool no_signaling_nans;
 } float_status;
 
 #endif /* SOFTFLOAT_TYPES_H */