270 lines
11 KiB
C
Executable File
270 lines
11 KiB
C
Executable File
/*============================================================================
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This C source fragment is part of the SoftFloat IEC/IEEE Floating-point
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Arithmetic Package, Release 2b.
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Written by John R. Hauser. This work was made possible in part by the
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International Computer Science Institute, located at Suite 600, 1947 Center
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Street, Berkeley, California 94704. Funding was partially provided by the
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National Science Foundation under grant MIP-9311980. The original version
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of this code was written as part of a project to build a fixed-point vector
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processor in collaboration with the University of California at Berkeley,
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overseen by Profs. Nelson Morgan and John Wawrzynek. More information
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is available through the Web page `http://www.cs.berkeley.edu/~jhauser/
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arithmetic/SoftFloat.html'.
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THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE. Although reasonable effort has
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been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT TIMES
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RESULT IN INCORRECT BEHAVIOR. USE OF THIS SOFTWARE IS RESTRICTED TO PERSONS
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AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ALL LOSSES,
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COSTS, OR OTHER PROBLEMS THEY INCUR DUE TO THE SOFTWARE, AND WHO FURTHERMORE
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EFFECTIVELY INDEMNIFY JOHN HAUSER AND THE INTERNATIONAL COMPUTER SCIENCE
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INSTITUTE (possibly via similar legal warning) AGAINST ALL LOSSES, COSTS, OR
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OTHER PROBLEMS INCURRED BY THEIR CUSTOMERS AND CLIENTS DUE TO THE SOFTWARE.
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Derivative works are acceptable, even for commercial purposes, so long as
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(1) the source code for the derivative work includes prominent notice that
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the work is derivative, and (2) the source code includes prominent notice with
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these four paragraphs for those parts of this code that are retained.
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=============================================================================*/
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/*============================================================================
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* Adapted for Bochs (x86 achitecture simulator) by
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* Stanislav Shwartsman (gate@fidonet.org.il)
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* ==========================================================================*/
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typedef int flag;
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/*----------------------------------------------------------------------------
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| Raises the exceptions specified by `flags'. Floating-point traps can be
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| defined here if desired. It is currently not possible for such a trap
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| to substitute a result value. If traps are not implemented, this routine
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| should be simply `float_exception_flags |= flags;'
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*----------------------------------------------------------------------------*/
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BX_CPP_INLINE void float_raise(float_status_t &status, int flags)
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{
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status.float_exception_flags |= flags;
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}
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/*----------------------------------------------------------------------------
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| Returns current floating point rounding mode specified by status word.
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*----------------------------------------------------------------------------*/
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BX_CPP_INLINE int get_float_rounding_mode(float_status_t &status)
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{
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return status.float_rounding_mode;
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}
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/*----------------------------------------------------------------------------
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| Returns current floating point NaN operands handling mode specified
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| by status word.
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*----------------------------------------------------------------------------*/
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BX_CPP_INLINE int get_float_nan_handling_mode(float_status_t &status)
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{
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return status.float_nan_handling_mode;
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}
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/*----------------------------------------------------------------------------
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| Returns 1 if the <flush-underflow-to-zero> feature is supported;
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| otherwise returns 0.
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*----------------------------------------------------------------------------*/
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BX_CPP_INLINE int get_flush_underflow_to_zero(float_status_t &status)
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{
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return status.flush_underflow_to_zero;
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}
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/*----------------------------------------------------------------------------
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| Internal canonical NaN format.
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*----------------------------------------------------------------------------*/
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typedef struct {
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flag sign;
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Bit64u hi, lo;
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} commonNaNT;
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/*----------------------------------------------------------------------------
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| The pattern for a default generated single-precision NaN.
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*----------------------------------------------------------------------------*/
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#define float32_default_nan 0xFFC00000
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/* in another version
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#define float32_default_nan 0x7FFFFFFF
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*/
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/*----------------------------------------------------------------------------
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| Returns 1 if the single-precision floating-point value `a' is a NaN;
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| otherwise returns 0.
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*----------------------------------------------------------------------------*/
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int float32_is_nan(float32 a)
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{
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return (0xFF000000 < (Bit32u) (a<<1));
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}
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/*----------------------------------------------------------------------------
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| Returns 1 if the single-precision floating-point value `a' is a signaling
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| NaN; otherwise returns 0.
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*----------------------------------------------------------------------------*/
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int float32_is_signaling_nan(float32 a)
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{
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return (((a>>22) & 0x1FF) == 0x1FE) && (a & 0x003FFFFF);
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}
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/*----------------------------------------------------------------------------
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| Returns the result of converting the single-precision floating-point NaN
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| `a' to the canonical NaN format. If `a' is a signaling NaN, the invalid
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| exception is raised.
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*----------------------------------------------------------------------------*/
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static commonNaNT float32ToCommonNaN(float32 a, float_status_t &status)
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{
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commonNaNT z;
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if (float32_is_signaling_nan(a)) float_raise(status, float_flag_invalid);
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z.sign = a>>31;
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z.lo = 0;
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z.hi = ((Bit64u) a)<<41;
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return z;
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}
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/*----------------------------------------------------------------------------
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| Returns the result of converting the canonical NaN `a' to the single-
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| precision floating-point format.
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*----------------------------------------------------------------------------*/
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static float32 commonNaNToFloat32(commonNaNT a)
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{
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return (((Bit32u) a.sign)<<31) | 0x7FC00000 | (a.hi>>41);
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}
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/*----------------------------------------------------------------------------
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| Takes two single-precision floating-point values `a' and `b', one of which
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| is a NaN, and returns the appropriate NaN result. If either `a' or `b' is a
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| signaling NaN, the invalid exception is raised.
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*----------------------------------------------------------------------------*/
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static float32 propagateFloat32NaN(float32 a, float32 b, float_status_t &status)
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{
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flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN;
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aIsNaN = float32_is_nan(a);
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aIsSignalingNaN = float32_is_signaling_nan(a);
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bIsNaN = float32_is_nan(b);
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bIsSignalingNaN = float32_is_signaling_nan(b);
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a |= 0x00400000;
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b |= 0x00400000;
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if (aIsSignalingNaN | bIsSignalingNaN) float_raise(status, float_flag_invalid);
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if (get_float_nan_handling_mode(status) == float_larger_significand_nan) {
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if (aIsSignalingNaN) {
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if (bIsSignalingNaN) goto returnLargerSignificand;
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return bIsNaN ? b : a;
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}
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else if (aIsNaN) {
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if (bIsSignalingNaN | ! bIsNaN) return a;
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returnLargerSignificand:
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if ((Bit32u) (a<<1) < (Bit32u) (b<<1)) return b;
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if ((Bit32u) (b<<1) < (Bit32u) (a<<1)) return a;
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return (a < b) ? a : b;
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}
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else {
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return b;
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}
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} else {
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return (aIsSignalingNaN | aIsNaN) ? a : b;
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}
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}
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/*----------------------------------------------------------------------------
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| The pattern for a default generated double-precision NaN.
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*----------------------------------------------------------------------------*/
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#define float64_default_nan BX_CONST64(0xFFF8000000000000)
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/* in another version
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#define float64_default_nan BX_CONST64(0x7FFFFFFFFFFFFFFF)
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*/
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/*----------------------------------------------------------------------------
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| Returns 1 if the double-precision floating-point value `a' is a NaN;
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| otherwise returns 0.
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*----------------------------------------------------------------------------*/
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int float64_is_nan(float64 a)
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{
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return (BX_CONST64(0xFFE0000000000000) < (Bit64u) (a<<1));
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}
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/*----------------------------------------------------------------------------
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| Returns 1 if the double-precision floating-point value `a' is a signaling
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| NaN; otherwise returns 0.
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*----------------------------------------------------------------------------*/
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int float64_is_signaling_nan(float64 a)
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{
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return (((a>>51) & 0xFFF) == 0xFFE) && (a & BX_CONST64(0x0007FFFFFFFFFFFF));
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}
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/*----------------------------------------------------------------------------
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| Returns the result of converting the double-precision floating-point NaN
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| `a' to the canonical NaN format. If `a' is a signaling NaN, the invalid
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| exception is raised.
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*----------------------------------------------------------------------------*/
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static commonNaNT float64ToCommonNaN(float64 a, float_status_t &status)
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{
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commonNaNT z;
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if (float64_is_signaling_nan(a)) float_raise(status, float_flag_invalid);
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z.sign = a>>63;
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z.lo = 0;
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z.hi = a<<12;
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return z;
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}
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/*----------------------------------------------------------------------------
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| Returns the result of converting the canonical NaN `a' to the double-
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| precision floating-point format.
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*----------------------------------------------------------------------------*/
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static float64 commonNaNToFloat64(commonNaNT a)
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{
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return (((Bit64u) a.sign)<<63) | BX_CONST64(0x7FF8000000000000) | (a.hi>>12);
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}
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/*----------------------------------------------------------------------------
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| Takes two double-precision floating-point values `a' and `b', one of which
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| is a NaN, and returns the appropriate NaN result. If either `a' or `b' is a
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| signaling NaN, the invalid exception is raised.
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*----------------------------------------------------------------------------*/
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static float64 propagateFloat64NaN(float64 a, float64 b, float_status_t &status)
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{
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flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN;
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aIsNaN = float64_is_nan(a);
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aIsSignalingNaN = float64_is_signaling_nan(a);
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bIsNaN = float64_is_nan(b);
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bIsSignalingNaN = float64_is_signaling_nan(b);
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a |= BX_CONST64(0x0008000000000000);
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b |= BX_CONST64(0x0008000000000000);
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if (aIsSignalingNaN | bIsSignalingNaN) float_raise(status, float_flag_invalid);
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if (get_float_nan_handling_mode(status) == float_larger_significand_nan) {
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if (aIsSignalingNaN) {
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if (bIsSignalingNaN) goto returnLargerSignificand;
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return bIsNaN ? b : a;
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}
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else if (aIsNaN) {
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if (bIsSignalingNaN | ! bIsNaN) return a;
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returnLargerSignificand:
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if ((Bit64u) (a<<1) < (Bit64u) (b<<1)) return b;
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if ((Bit64u) (b<<1) < (Bit64u) (a<<1)) return a;
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return (a < b) ? a : b;
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}
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else {
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return b;
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}
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} else {
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return (aIsSignalingNaN | aIsNaN) ? a : b;
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}
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}
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