diff options
| -rw-r--r-- | fpu/softfloat-specialize.h | 160 |
1 files changed, 100 insertions, 60 deletions
diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h index f382f7a00c..8dcf469ee6 100644 --- a/fpu/softfloat-specialize.h +++ b/fpu/softfloat-specialize.h @@ -153,6 +153,52 @@ static float32 commonNaNToFloat32( commonNaNT a ) } /*---------------------------------------------------------------------------- +| Select which NaN to propagate for a two-input operation. +| IEEE754 doesn't specify all the details of this, so the +| algorithm is target-specific. +| The routine is passed various bits of information about the +| two NaNs and should return 0 to select NaN a and 1 for NaN b. +| Note that signalling NaNs are always squashed to quiet NaNs +| by the caller, by flipping the SNaN bit before returning them. +| +| aIsLargerSignificand is only valid if both a and b are NaNs +| of some kind, and is true if a has the larger significand, +| or if both a and b have the same significand but a is +| positive but b is negative. It is only needed for the x87 +| tie-break rule. +*----------------------------------------------------------------------------*/ + +static int pickNaN(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN, + flag aIsLargerSignificand) +{ + /* This implements x87 NaN propagation rules: + * SNaN + QNaN => return the QNaN + * two SNaNs => return the one with the larger significand, silenced + * two QNaNs => return the one with the larger significand + * SNaN and a non-NaN => return the SNaN, silenced + * QNaN and a non-NaN => return the QNaN + * + * If we get down to comparing significands and they are the same, + * return the NaN with the positive sign bit (if any). + */ + if (aIsSNaN) { + if (bIsSNaN) { + return aIsLargerSignificand ? 0 : 1; + } + return bIsQNaN ? 1 : 0; + } + else if (aIsQNaN) { + if (bIsSNaN || !bIsQNaN) + return 0; + else { + return aIsLargerSignificand ? 0 : 1; + } + } else { + return 1; + } +} + +/*---------------------------------------------------------------------------- | Takes two single-precision floating-point values `a' and `b', one of which | is a NaN, and returns the appropriate NaN result. If either `a' or `b' is a | signaling NaN, the invalid exception is raised. @@ -160,7 +206,7 @@ static float32 commonNaNToFloat32( commonNaNT a ) static float32 propagateFloat32NaN( float32 a, float32 b STATUS_PARAM) { - flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN; + flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN, aIsLargerSignificand; bits32 av, bv, res; if ( STATUS(default_nan_mode) ) @@ -180,26 +226,22 @@ static float32 propagateFloat32NaN( float32 a, float32 b STATUS_PARAM) bv |= 0x00400000; #endif if ( aIsSignalingNaN | bIsSignalingNaN ) float_raise( float_flag_invalid STATUS_VAR); - if ( aIsSignalingNaN ) { - if ( bIsSignalingNaN ) goto returnLargerSignificand; - res = bIsNaN ? bv : av; - } - else if ( aIsNaN ) { - if ( bIsSignalingNaN || ! bIsNaN ) - res = av; - else { - returnLargerSignificand: - if ( (bits32) ( av<<1 ) < (bits32) ( bv<<1 ) ) - res = bv; - else if ( (bits32) ( bv<<1 ) < (bits32) ( av<<1 ) ) - res = av; - else - res = ( av < bv ) ? av : bv; - } + + if ((bits32)(av<<1) < (bits32)(bv<<1)) { + aIsLargerSignificand = 0; + } else if ((bits32)(bv<<1) < (bits32)(av<<1)) { + aIsLargerSignificand = 1; + } else { + aIsLargerSignificand = (av < bv) ? 1 : 0; } - else { + + if (pickNaN(aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN, + aIsLargerSignificand)) { res = bv; + } else { + res = av; } + return make_float32(res); } @@ -314,7 +356,7 @@ static float64 commonNaNToFloat64( commonNaNT a ) static float64 propagateFloat64NaN( float64 a, float64 b STATUS_PARAM) { - flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN; + flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN, aIsLargerSignificand; bits64 av, bv, res; if ( STATUS(default_nan_mode) ) @@ -334,26 +376,22 @@ static float64 propagateFloat64NaN( float64 a, float64 b STATUS_PARAM) bv |= LIT64( 0x0008000000000000 ); #endif if ( aIsSignalingNaN | bIsSignalingNaN ) float_raise( float_flag_invalid STATUS_VAR); - if ( aIsSignalingNaN ) { - if ( bIsSignalingNaN ) goto returnLargerSignificand; - res = bIsNaN ? bv : av; - } - else if ( aIsNaN ) { - if ( bIsSignalingNaN || ! bIsNaN ) - res = av; - else { - returnLargerSignificand: - if ( (bits64) ( av<<1 ) < (bits64) ( bv<<1 ) ) - res = bv; - else if ( (bits64) ( bv<<1 ) < (bits64) ( av<<1 ) ) - res = av; - else - res = ( av < bv ) ? av : bv; - } + + if ((bits64)(av<<1) < (bits64)(bv<<1)) { + aIsLargerSignificand = 0; + } else if ((bits64)(bv<<1) < (bits64)(av<<1)) { + aIsLargerSignificand = 1; + } else { + aIsLargerSignificand = (av < bv) ? 1 : 0; } - else { + + if (pickNaN(aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN, + aIsLargerSignificand)) { res = bv; + } else { + res = av; } + return make_float64(res); } @@ -454,7 +492,7 @@ static floatx80 commonNaNToFloatx80( commonNaNT a ) static floatx80 propagateFloatx80NaN( floatx80 a, floatx80 b STATUS_PARAM) { - flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN; + flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN, aIsLargerSignificand; if ( STATUS(default_nan_mode) ) { a.low = floatx80_default_nan_low; @@ -474,19 +512,20 @@ static floatx80 propagateFloatx80NaN( floatx80 a, floatx80 b STATUS_PARAM) b.low |= LIT64( 0xC000000000000000 ); #endif if ( aIsSignalingNaN | bIsSignalingNaN ) float_raise( float_flag_invalid STATUS_VAR); - if ( aIsSignalingNaN ) { - if ( bIsSignalingNaN ) goto returnLargerSignificand; - return bIsNaN ? b : a; - } - else if ( aIsNaN ) { - if ( bIsSignalingNaN || ! bIsNaN ) return a; - returnLargerSignificand: - if ( a.low < b.low ) return b; - if ( b.low < a.low ) return a; - return ( a.high < b.high ) ? a : b; + + if (a.low < b.low) { + aIsLargerSignificand = 0; + } else if (b.low < a.low) { + aIsLargerSignificand = 1; + } else { + aIsLargerSignificand = (a.high < b.high) ? 1 : 0; } - else { + + if (pickNaN(aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN, + aIsLargerSignificand)) { return b; + } else { + return a; } } @@ -580,7 +619,7 @@ static float128 commonNaNToFloat128( commonNaNT a ) static float128 propagateFloat128NaN( float128 a, float128 b STATUS_PARAM) { - flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN; + flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN, aIsLargerSignificand; if ( STATUS(default_nan_mode) ) { a.low = float128_default_nan_low; @@ -600,19 +639,20 @@ static float128 propagateFloat128NaN( float128 a, float128 b STATUS_PARAM) b.high |= LIT64( 0x0000800000000000 ); #endif if ( aIsSignalingNaN | bIsSignalingNaN ) float_raise( float_flag_invalid STATUS_VAR); - if ( aIsSignalingNaN ) { - if ( bIsSignalingNaN ) goto returnLargerSignificand; - return bIsNaN ? b : a; - } - else if ( aIsNaN ) { - if ( bIsSignalingNaN || ! bIsNaN ) return a; - returnLargerSignificand: - if ( lt128( a.high<<1, a.low, b.high<<1, b.low ) ) return b; - if ( lt128( b.high<<1, b.low, a.high<<1, a.low ) ) return a; - return ( a.high < b.high ) ? a : b; + + if (lt128(a.high<<1, a.low, b.high<<1, b.low)) { + aIsLargerSignificand = 0; + } else if (lt128(b.high<<1, b.low, a.high<<1, a.low)) { + aIsLargerSignificand = 1; + } else { + aIsLargerSignificand = (a.high < b.high) ? 1 : 0; } - else { + + if (pickNaN(aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN, + aIsLargerSignificand)) { return b; + } else { + return a; } } |