* [Qemu-devel] [PATCH v2] Softfloat: Add support to softfloat to return floatxx_default_nan when, the corresponding target status flag is set.
@ 2011-02-07 15:30 Christophe Lyon
2011-02-07 16:48 ` Peter Maydell
0 siblings, 1 reply; 2+ messages in thread
From: Christophe Lyon @ 2011-02-07 15:30 UTC (permalink / raw)
To: qemu-devel@nongnu.org
Some CPUs have a status flag imposing to return floatxx_default_nan
whatever the input value, when converting from one FP format to
another. Implement this, using the already existing default_nan_mode
status flag (currently used on ARM and SH4 at the moment).
Signed-off-by: Christophe Lyon <christophe.lyon@st.com>
---
Note that I am unsure whether it's useful to have a default (ie non-ARM) value for float16_default_nan and if the value I've used is right.
fpu/softfloat-specialize.h | 57 ++++++++++++++++++++++++++++++++++++++++---
fpu/softfloat.c | 30 ++++++++++-------------
2 files changed, 66 insertions(+), 21 deletions(-)
diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
index 11521ce..997da36 100644
--- a/fpu/softfloat-specialize.h
+++ b/fpu/softfloat-specialize.h
@@ -144,9 +144,14 @@ static commonNaNT float32ToCommonNaN( float32 a STATUS_PARAM )
| precision floating-point format.
*----------------------------------------------------------------------------*/
-static float32 commonNaNToFloat32( commonNaNT a )
+static float32 commonNaNToFloat32( commonNaNT a STATUS_PARAM)
{
bits32 mantissa = a.high>>41;
+
+ if ( STATUS(default_nan_mode) ) {
+ return float32_default_nan;
+ }
+
if ( mantissa )
return make_float32(
( ( (bits32) a.sign )<<31 ) | 0x7F800000 | ( a.high>>41 ) );
@@ -398,10 +403,14 @@ static commonNaNT float64ToCommonNaN( float64 a STATUS_PARAM)
| precision floating-point format.
*----------------------------------------------------------------------------*/
-static float64 commonNaNToFloat64( commonNaNT a )
+static float64 commonNaNToFloat64( commonNaNT a STATUS_PARAM)
{
bits64 mantissa = a.high>>12;
+ if ( STATUS(default_nan_mode) ) {
+ return float64_default_nan;
+ }
+
if ( mantissa )
return make_float64(
( ( (bits64) a.sign )<<63 )
@@ -451,6 +460,34 @@ static float64 propagateFloat64NaN( float64 a, float64 b STATUS_PARAM)
}
}
+/*----------------------------------------------------------------------------
+| The pattern for a default generated haft-precision NaN.
+*----------------------------------------------------------------------------*/
+#if defined(TARGET_ARM)
+#define float16_default_nan 0x7E00
+#else
+#define float16_default_nan 0xFE00
+#endif
+
+/*----------------------------------------------------------------------------
+| Returns the result of converting the canonical NaN `a' to the half-
+| precision floating-point format.
+*----------------------------------------------------------------------------*/
+
+static bits16 commonNaNToFloat16( commonNaNT a STATUS_PARAM)
+{
+ bits16 mantissa = a.high>>57;
+
+ if ( STATUS(default_nan_mode) ) {
+ return float16_default_nan;
+ }
+
+ if ( mantissa )
+ return (bits16)a.sign << 15 | 0x1F << 10 | mantissa;
+ else
+ return float16_default_nan;
+}
+
#ifdef FLOATX80
/*----------------------------------------------------------------------------
@@ -551,10 +588,16 @@ static commonNaNT floatx80ToCommonNaN( floatx80 a STATUS_PARAM)
| double-precision floating-point format.
*----------------------------------------------------------------------------*/
-static floatx80 commonNaNToFloatx80( commonNaNT a )
+static floatx80 commonNaNToFloatx80( commonNaNT a STATUS_PARAM)
{
floatx80 z;
+ if ( STATUS(default_nan_mode) ) {
+ z.low = floatx80_default_nan_low;
+ z.high = floatx80_default_nan_high;
+ return z;
+ }
+
if (a.high)
z.low = a.high;
else
@@ -699,10 +742,16 @@ static commonNaNT float128ToCommonNaN( float128 a STATUS_PARAM)
| precision floating-point format.
*----------------------------------------------------------------------------*/
-static float128 commonNaNToFloat128( commonNaNT a )
+static float128 commonNaNToFloat128( commonNaNT a STATUS_PARAM)
{
float128 z;
+ if ( STATUS(default_nan_mode) ) {
+ z.low = float128_default_nan_low;
+ z.high = float128_default_nan_high;
+ return z;
+ }
+
shift128Right( a.high, a.low, 16, &z.high, &z.low );
z.high |= ( ( (bits64) a.sign )<<63 ) | LIT64( 0x7FFF000000000000 );
return z;
diff --git a/fpu/softfloat.c b/fpu/softfloat.c
index 17842f4..abf14f1 100644
--- a/fpu/softfloat.c
+++ b/fpu/softfloat.c
@@ -1534,7 +1534,7 @@ float64 float32_to_float64( float32 a STATUS_PARAM )
aExp = extractFloat32Exp( a );
aSign = extractFloat32Sign( a );
if ( aExp == 0xFF ) {
- if ( aSig ) return commonNaNToFloat64( float32ToCommonNaN( a STATUS_VAR ));
+ if ( aSig ) return commonNaNToFloat64( float32ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
return packFloat64( aSign, 0x7FF, 0 );
}
if ( aExp == 0 ) {
@@ -1566,7 +1566,7 @@ floatx80 float32_to_floatx80( float32 a STATUS_PARAM )
aExp = extractFloat32Exp( a );
aSign = extractFloat32Sign( a );
if ( aExp == 0xFF ) {
- if ( aSig ) return commonNaNToFloatx80( float32ToCommonNaN( a STATUS_VAR ) );
+ if ( aSig ) return commonNaNToFloatx80( float32ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
return packFloatx80( aSign, 0x7FFF, LIT64( 0x8000000000000000 ) );
}
if ( aExp == 0 ) {
@@ -1600,7 +1600,7 @@ float128 float32_to_float128( float32 a STATUS_PARAM )
aExp = extractFloat32Exp( a );
aSign = extractFloat32Sign( a );
if ( aExp == 0xFF ) {
- if ( aSig ) return commonNaNToFloat128( float32ToCommonNaN( a STATUS_VAR ) );
+ if ( aSig ) return commonNaNToFloat128( float32ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
return packFloat128( aSign, 0x7FFF, 0, 0 );
}
if ( aExp == 0 ) {
@@ -2689,7 +2689,7 @@ float32 float64_to_float32( float64 a STATUS_PARAM )
aExp = extractFloat64Exp( a );
aSign = extractFloat64Sign( a );
if ( aExp == 0x7FF ) {
- if ( aSig ) return commonNaNToFloat32( float64ToCommonNaN( a STATUS_VAR ) );
+ if ( aSig ) return commonNaNToFloat32( float64ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
return packFloat32( aSign, 0xFF, 0 );
}
shift64RightJamming( aSig, 22, &aSig );
@@ -2767,11 +2767,7 @@ bits16 float32_to_float16( float32 a, flag ieee STATUS_PARAM)
aExp = extractFloat32Exp( a );
aSign = extractFloat32Sign( a );
if ( aExp == 0xFF ) {
- if (aSig) {
- /* Make sure correct exceptions are raised. */
- float32ToCommonNaN(a STATUS_VAR);
- aSig |= 0x00400000;
- }
+ if ( aSig ) return commonNaNToFloat16( float32ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
return packFloat16(aSign, 0x1f, aSig >> 13);
}
if (aExp == 0 && aSign == 0) {
@@ -2861,7 +2857,7 @@ floatx80 float64_to_floatx80( float64 a STATUS_PARAM )
aExp = extractFloat64Exp( a );
aSign = extractFloat64Sign( a );
if ( aExp == 0x7FF ) {
- if ( aSig ) return commonNaNToFloatx80( float64ToCommonNaN( a STATUS_VAR ) );
+ if ( aSig ) return commonNaNToFloatx80( float64ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
return packFloatx80( aSign, 0x7FFF, LIT64( 0x8000000000000000 ) );
}
if ( aExp == 0 ) {
@@ -2896,7 +2892,7 @@ float128 float64_to_float128( float64 a STATUS_PARAM )
aExp = extractFloat64Exp( a );
aSign = extractFloat64Sign( a );
if ( aExp == 0x7FF ) {
- if ( aSig ) return commonNaNToFloat128( float64ToCommonNaN( a STATUS_VAR ) );
+ if ( aSig ) return commonNaNToFloat128( float64ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
return packFloat128( aSign, 0x7FFF, 0, 0 );
}
if ( aExp == 0 ) {
@@ -3843,7 +3839,7 @@ float32 floatx80_to_float32( floatx80 a STATUS_PARAM )
aSign = extractFloatx80Sign( a );
if ( aExp == 0x7FFF ) {
if ( (bits64) ( aSig<<1 ) ) {
- return commonNaNToFloat32( floatx80ToCommonNaN( a STATUS_VAR ) );
+ return commonNaNToFloat32( floatx80ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
}
return packFloat32( aSign, 0xFF, 0 );
}
@@ -3871,7 +3867,7 @@ float64 floatx80_to_float64( floatx80 a STATUS_PARAM )
aSign = extractFloatx80Sign( a );
if ( aExp == 0x7FFF ) {
if ( (bits64) ( aSig<<1 ) ) {
- return commonNaNToFloat64( floatx80ToCommonNaN( a STATUS_VAR ) );
+ return commonNaNToFloat64( floatx80ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
}
return packFloat64( aSign, 0x7FF, 0 );
}
@@ -3900,7 +3896,7 @@ float128 floatx80_to_float128( floatx80 a STATUS_PARAM )
aExp = extractFloatx80Exp( a );
aSign = extractFloatx80Sign( a );
if ( ( aExp == 0x7FFF ) && (bits64) ( aSig<<1 ) ) {
- return commonNaNToFloat128( floatx80ToCommonNaN( a STATUS_VAR ) );
+ return commonNaNToFloat128( floatx80ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
}
shift128Right( aSig<<1, 0, 16, &zSig0, &zSig1 );
return packFloat128( aSign, aExp, zSig0, zSig1 );
@@ -4863,7 +4859,7 @@ float32 float128_to_float32( float128 a STATUS_PARAM )
aSign = extractFloat128Sign( a );
if ( aExp == 0x7FFF ) {
if ( aSig0 | aSig1 ) {
- return commonNaNToFloat32( float128ToCommonNaN( a STATUS_VAR ) );
+ return commonNaNToFloat32( float128ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
}
return packFloat32( aSign, 0xFF, 0 );
}
@@ -4897,7 +4893,7 @@ float64 float128_to_float64( float128 a STATUS_PARAM )
aSign = extractFloat128Sign( a );
if ( aExp == 0x7FFF ) {
if ( aSig0 | aSig1 ) {
- return commonNaNToFloat64( float128ToCommonNaN( a STATUS_VAR ) );
+ return commonNaNToFloat64( float128ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
}
return packFloat64( aSign, 0x7FF, 0 );
}
@@ -4932,7 +4928,7 @@ floatx80 float128_to_floatx80( float128 a STATUS_PARAM )
aSign = extractFloat128Sign( a );
if ( aExp == 0x7FFF ) {
if ( aSig0 | aSig1 ) {
- return commonNaNToFloatx80( float128ToCommonNaN( a STATUS_VAR ) );
+ return commonNaNToFloatx80( float128ToCommonNaN( a STATUS_VAR ) STATUS_VAR );
}
return packFloatx80( aSign, 0x7FFF, LIT64( 0x8000000000000000 ) );
}
--
1.7.2.3
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Qemu-devel] [PATCH v2] Softfloat: Add support to softfloat to return floatxx_default_nan when, the corresponding target status flag is set.
2011-02-07 15:30 [Qemu-devel] [PATCH v2] Softfloat: Add support to softfloat to return floatxx_default_nan when, the corresponding target status flag is set Christophe Lyon
@ 2011-02-07 16:48 ` Peter Maydell
0 siblings, 0 replies; 2+ messages in thread
From: Peter Maydell @ 2011-02-07 16:48 UTC (permalink / raw)
To: Christophe Lyon; +Cc: qemu-devel@nongnu.org
On 7 February 2011 15:30, Christophe Lyon <christophe.lyon@st.com> wrote:
> Note that I am unsure whether it's useful to have a default (ie non-ARM) value for float16_default_nan and if the value I've used is right.
We should set the default consistent with how we do it for
the other types: special cases for various architectures,
default for SNAN_BIT_IS_ONE is sign=0,exp=1....1,
mantissa=01.....1; default for !SNAN_BIT_IS_ONE is
sign=1,exp=1.....1,mantissa=0....0. So:
#if defined(TARGET_ARM)
#define float16_default_nan 0x7E00
#elif SNAN_BIT_IS_ONE
#define float16_default_nan 0x7DFF
#else
#define float16_default_nan 0xFE00
#endif
> +static bits16 commonNaNToFloat16( commonNaNT a STATUS_PARAM)
> +{
> + bits16 mantissa = a.high>>57;
> +
> + if ( STATUS(default_nan_mode) ) {
> + return float16_default_nan;
> + }
> +
> + if ( mantissa )
> + return (bits16)a.sign << 15 | 0x1F << 10 | mantissa;
> + else
> + return float16_default_nan;
> +}
Could we have some brackets around the shifts and some braces
for this if(), please? (I know most of softfloat doesn't adhere to
the qemu brace-standard, and I'm not going to ask for all those
other ifs to change, but since this is a new function we might as
well put in the braces for this one.)
thanks
-- PMM
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2011-02-07 15:30 [Qemu-devel] [PATCH v2] Softfloat: Add support to softfloat to return floatxx_default_nan when, the corresponding target status flag is set Christophe Lyon
2011-02-07 16:48 ` Peter Maydell
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