xref: /src/lib/libc/softfloat/softfloat-specialize

/*	$NetBSD: softfloat-specialize,v 1.10 2025/04/27 15:23:27 riastradh Exp $	*/

/* This is a derivative work. */

/*
===============================================================================

This C source fragment is part of the SoftFloat IEC/IEEE Floating-point
Arithmetic Package, Release 2a.

Written by John R. Hauser.  This work was made possible in part by the
International Computer Science Institute, located at Suite 600, 1947 Center
Street, Berkeley, California 94704.  Funding was partially provided by the
National Science Foundation under grant MIP-9311980.  The original version
of this code was written as part of a project to build a fixed-point vector
processor in collaboration with the University of California at Berkeley,
overseen by Profs. Nelson Morgan and John Wawrzynek.  More information
is available through the Web page `http://HTTP.CS.Berkeley.EDU/~jhauser/
arithmetic/SoftFloat.html'.

THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE.  Although reasonable effort
has been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT
TIMES RESULT IN INCORRECT BEHAVIOR.  USE OF THIS SOFTWARE IS RESTRICTED TO
PERSONS AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ANY
AND ALL LOSSES, COSTS, OR OTHER PROBLEMS ARISING FROM ITS USE.

Derivative works are acceptable, even for commercial purposes, so long as
(1) they include prominent notice that the work is derivative, and (2) they
include prominent notice akin to these four paragraphs for those parts of
this code that are retained.

===============================================================================
*/

#include <signal.h>
#include <string.h>
#include <unistd.h>

#include "reentrant.h"

/*
-------------------------------------------------------------------------------
Underflow tininess-detection mode, statically initialized to default value.
(The declaration in `softfloat.h' must match the `int8' type here.)
-------------------------------------------------------------------------------
*/
#ifdef SOFTFLOAT_FOR_GCC
static
#endif
int8 float_detect_tininess = float_tininess_after_rounding;

/*
-------------------------------------------------------------------------------
Raises the exceptions specified by `flags'.  Floating-point traps can be
defined here if desired.  It is currently not possible for such a trap to
substitute a result value.  If traps are not implemented, this routine
should be simply `float_exception_flags |= flags;'.
-------------------------------------------------------------------------------
*/
#ifdef SOFTFLOAT_FOR_GCC
#ifndef set_float_exception_mask
#define float_exception_mask	_softfloat_float_exception_mask
#endif
#endif
#ifndef set_float_exception_mask
fp_except float_exception_mask = 0;
#endif
void
float_raise( fp_except newflags )
{
    siginfo_t info;
    struct sigaction sa;
    sigset_t sigmask, osigmask;
    fp_except flags;

    for (;;) {
#ifdef set_float_exception_mask
	flags = newflags | set_float_exception_flags(newflags, 0);
#else
	float_exception_flags |= newflags;
	flags = float_exception_flags;
#endif

	/*
	 * If none of the sticky flags are trapped (i.e., enabled in
	 * float_exception_mask), we're done.  Trapping is unusual and
	 * costly anyway, so take the non-trapping path as the fast
	 * path.
	 */
	flags &= float_exception_mask;
	if (__predict_true(flags == 0))
	    break;

	/*
	 * Block all signals while we figure out how to deliver a
	 * non-maskable (as a signal), non-ignorable SIGFPE, and obtain
	 * the current signal mask.
	 */
	sigfillset(&sigmask);
	thr_sigsetmask(SIG_BLOCK, &sigmask, &osigmask);

	/*
	 * Find the current signal disposition of SIGFPE.
	 */
	sigaction(SIGFPE, NULL, &sa);

	/*
	 * If SIGFPE is masked or ignored, unmask it and reset it to
	 * the default disposition to deliver the signal.
	 */
	if (sigismember(&osigmask, SIGFPE) ||
	    ((sa.sa_flags & SA_SIGINFO) == 0 &&
		sa.sa_handler == SIG_IGN)) {
		/*
		 * Prepare to unmask SIGFPE.  This will take effect
		 * when we use thr_sigsetmask(SIG_SETMASK, ...) below,
		 * once the signal has been queued, so that it happens
		 * atomically with respect to other signal delivery.
		 */
		sigdelset(&osigmask, SIGFPE);

		/*
		 * Reset SIGFPE to the default disposition, which is to
		 * terminate the process.
		 */
		memset(&sa, 0, sizeof(sa));
		sa.sa_handler = SIG_DFL;
		sigemptyset(&sa.sa_mask);
		sa.sa_flags = 0;
		sigaction(SIGFPE, &sa, NULL);
	}

	/*
	 * Queue the signal for delivery.  It won't trigger the signal
	 * handler yet, because it's still masked, but as soon as we
	 * unmask it either the process will terminate or the signal
	 * handler will be called.
	 */
	memset(&info, 0, sizeof info);
	info.si_signo = SIGFPE;
	info.si_pid = getpid();
	info.si_uid = geteuid();
	if (flags & float_flag_underflow)
	    info.si_code = FPE_FLTUND;
	else if (flags & float_flag_overflow)
	    info.si_code = FPE_FLTOVF;
	else if (flags & float_flag_divbyzero)
	    info.si_code = FPE_FLTDIV;
	else if (flags & float_flag_invalid)
	    info.si_code = FPE_FLTINV;
	else if (flags & float_flag_inexact)
	    info.si_code = FPE_FLTRES;
	sigqueueinfo(getpid(), &info);

	/*
	 * Restore the old signal mask, except with SIGFPE unmasked
	 * even if it was masked before.
	 *
	 * At this point, either the process will terminate (if SIGFPE
	 * had or now has the default disposition) or the signal
	 * handler will be called (if SIGFPE had a non-default,
	 * non-ignored disposition).
	 *
	 * If the signal handler returns, it can't change the set of
	 * exceptions raised by this floating-point operation -- but it
	 * can change the sticky set from previous operations, and it
	 * can change the set of exceptions that are trapped, so loop
	 * around; next time we might make progress instead of calling
	 * the signal handler again.
	 */
	thr_sigsetmask(SIG_SETMASK, &osigmask, NULL);
    }
}
#undef float_exception_mask

/*
-------------------------------------------------------------------------------
Internal canonical NaN format.
-------------------------------------------------------------------------------
*/
typedef struct {
    flag sign;
    bits64 high, low;
} commonNaNT;

/*
-------------------------------------------------------------------------------
The pattern for a default generated single-precision NaN.
-------------------------------------------------------------------------------
*/
#define float32_default_nan 0xFFFFFFFF

/*
-------------------------------------------------------------------------------
Returns 1 if the single-precision floating-point value `a' is a NaN;
otherwise returns 0.
-------------------------------------------------------------------------------
*/
#ifdef SOFTFLOAT_FOR_GCC
static
#endif
flag float32_is_nan( float32 a )
{

    return ( (bits32)0xFF000000 < (bits32) ( a<<1 ) );

}

/*
-------------------------------------------------------------------------------
Returns 1 if the single-precision floating-point value `a' is a signaling
NaN; otherwise returns 0.
-------------------------------------------------------------------------------
*/
#if defined(SOFTFLOAT_FOR_GCC) \
    && !defined(SOFTFLOATAARCH64_FOR_GCC) \
    && !defined(SOFTFLOATSPARC64_FOR_GCC) \
    && !defined(SOFTFLOATM68K_FOR_GCC)
static
#endif
flag float32_is_signaling_nan( float32 a )
{

    return ( ( ( a>>22 ) & 0x1FF ) == 0x1FE ) && ( a & 0x003FFFFF );

}

/*
-------------------------------------------------------------------------------
Returns the result of converting the single-precision floating-point NaN
`a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
exception is raised.
-------------------------------------------------------------------------------
*/
static commonNaNT float32ToCommonNaN( float32 a )
{
    commonNaNT z;

    if ( float32_is_signaling_nan( a ) ) float_raise( float_flag_invalid );
    z.sign = a>>31;
    z.low = 0;
    z.high = ( (bits64) a )<<41;
    return z;

}

/*
-------------------------------------------------------------------------------
Returns the result of converting the canonical NaN `a' to the single-
precision floating-point format.
-------------------------------------------------------------------------------
*/
static float32 commonNaNToFloat32( commonNaNT a )
{

    return ( ( (bits32) a.sign )<<31 ) | 0x7FC00000 | (bits32)( a.high>>41 );

}

/*
-------------------------------------------------------------------------------
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.
-------------------------------------------------------------------------------
*/
static float32 propagateFloat32NaN( float32 a, float32 b )
{
    flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN;

    aIsNaN = float32_is_nan( a );
    aIsSignalingNaN = float32_is_signaling_nan( a );
    bIsNaN = float32_is_nan( b );
    bIsSignalingNaN = float32_is_signaling_nan( b );
    a |= 0x00400000;
    b |= 0x00400000;
    if ( aIsSignalingNaN | bIsSignalingNaN ) float_raise( float_flag_invalid );
    if ( aIsNaN ) {
        return ( aIsSignalingNaN & bIsNaN ) ? b : a;
    }
    else {
        return b;
    }

}

/*
-------------------------------------------------------------------------------
The pattern for a default generated double-precision NaN.
-------------------------------------------------------------------------------
*/
#define float64_default_nan LIT64( 0xFFFFFFFFFFFFFFFF )

/*
-------------------------------------------------------------------------------
Returns 1 if the double-precision floating-point value `a' is a NaN;
otherwise returns 0.
-------------------------------------------------------------------------------
*/
#ifdef SOFTFLOAT_FOR_GCC
static
#endif
flag float64_is_nan( float64 a )
{

    return ( (bits64)LIT64( 0xFFE0000000000000 ) <
	     (bits64) ( FLOAT64_DEMANGLE(a)<<1 ) );

}

/*
-------------------------------------------------------------------------------
Returns 1 if the double-precision floating-point value `a' is a signaling
NaN; otherwise returns 0.
-------------------------------------------------------------------------------
*/
#if defined(SOFTFLOAT_FOR_GCC) \
    && !defined(SOFTFLOATAARCH64_FOR_GCC) \
    && !defined(SOFTFLOATSPARC64_FOR_GCC) \
    && !defined(SOFTFLOATM68K_FOR_GCC)
static
#endif
flag float64_is_signaling_nan( float64 a )
{

    return
           ( ( ( FLOAT64_DEMANGLE(a)>>51 ) & 0xFFF ) == 0xFFE )
        && ( FLOAT64_DEMANGLE(a) & LIT64( 0x0007FFFFFFFFFFFF ) );

}

/*
-------------------------------------------------------------------------------
Returns the result of converting the double-precision floating-point NaN
`a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
exception is raised.
-------------------------------------------------------------------------------
*/
static commonNaNT float64ToCommonNaN( float64 a )
{
    commonNaNT z;

    if ( float64_is_signaling_nan( a ) ) float_raise( float_flag_invalid );
    z.sign = (flag)(FLOAT64_DEMANGLE(a)>>63);
    z.low = 0;
    z.high = FLOAT64_DEMANGLE(a)<<12;
    return z;

}

/*
-------------------------------------------------------------------------------
Returns the result of converting the canonical NaN `a' to the double-
precision floating-point format.
-------------------------------------------------------------------------------
*/
static float64 commonNaNToFloat64( commonNaNT a )
{

    return FLOAT64_MANGLE(
	( ( (bits64) a.sign )<<63 )
        | LIT64( 0x7FF8000000000000 )
        | ( a.high>>12 ) );

}

/*
-------------------------------------------------------------------------------
Takes two double-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.
-------------------------------------------------------------------------------
*/
static float64 propagateFloat64NaN( float64 a, float64 b )
{
    flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN;

    aIsNaN = float64_is_nan( a );
    aIsSignalingNaN = float64_is_signaling_nan( a );
    bIsNaN = float64_is_nan( b );
    bIsSignalingNaN = float64_is_signaling_nan( b );
    a |= FLOAT64_MANGLE(LIT64( 0x0008000000000000 ));
    b |= FLOAT64_MANGLE(LIT64( 0x0008000000000000 ));
    if ( aIsSignalingNaN | bIsSignalingNaN ) float_raise( float_flag_invalid );
    if ( aIsNaN ) {
        return ( aIsSignalingNaN & bIsNaN ) ? b : a;
    }
    else {
        return b;
    }

}

#ifdef FLOATX80

/*
-------------------------------------------------------------------------------
The pattern for a default generated extended double-precision NaN.  The
`high' and `low' values hold the most- and least-significant bits,
respectively.
-------------------------------------------------------------------------------
*/
#define floatx80_default_nan_high 0xFFFF
#define floatx80_default_nan_low  LIT64( 0xFFFFFFFFFFFFFFFF )

/*
-------------------------------------------------------------------------------
Returns 1 if the extended double-precision floating-point value `a' is a
NaN; otherwise returns 0.
-------------------------------------------------------------------------------
*/
flag floatx80_is_nan( floatx80 a )
{

    return ( ( a.high & 0x7FFF ) == 0x7FFF ) && (bits64) ( a.low<<1 );

}

/*
-------------------------------------------------------------------------------
Returns 1 if the extended double-precision floating-point value `a' is a
signaling NaN; otherwise returns 0.
-------------------------------------------------------------------------------
*/
flag floatx80_is_signaling_nan( floatx80 a )
{
    bits64 aLow;

    aLow = a.low & ~ LIT64( 0x4000000000000000 );
    return
           ( ( a.high & 0x7FFF ) == 0x7FFF )
        && (bits64) ( aLow<<1 )
        && ( a.low == aLow );

}

/*
-------------------------------------------------------------------------------
Returns the result of converting the extended double-precision floating-
point NaN `a' to the canonical NaN format.  If `a' is a signaling NaN, the
invalid exception is raised.
-------------------------------------------------------------------------------
*/
static commonNaNT floatx80ToCommonNaN( floatx80 a )
{
    commonNaNT z;

    if ( floatx80_is_signaling_nan( a ) ) float_raise( float_flag_invalid );
    z.sign = a.high>>15;
    z.low = 0;
    z.high = a.low<<1;
    return z;

}

/*
-------------------------------------------------------------------------------
Returns the result of converting the canonical NaN `a' to the extended
double-precision floating-point format.
-------------------------------------------------------------------------------
*/
static floatx80 commonNaNToFloatx80( commonNaNT a )
{
    floatx80 z;

    z.low = LIT64( 0xC000000000000000 ) | ( a.high>>1 );
    z.high = ( ( (bits16) a.sign )<<15 ) | 0x7FFF;
    return z;

}

/*
-------------------------------------------------------------------------------
Takes two extended double-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.
-------------------------------------------------------------------------------
*/
static floatx80 propagateFloatx80NaN( floatx80 a, floatx80 b )
{
    flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN;

    aIsNaN = floatx80_is_nan( a );
    aIsSignalingNaN = floatx80_is_signaling_nan( a );
    bIsNaN = floatx80_is_nan( b );
    bIsSignalingNaN = floatx80_is_signaling_nan( b );
    a.low |= LIT64( 0xC000000000000000 );
    b.low |= LIT64( 0xC000000000000000 );
    if ( aIsSignalingNaN | bIsSignalingNaN ) float_raise( float_flag_invalid );
    if ( aIsNaN ) {
        return ( aIsSignalingNaN & bIsNaN ) ? b : a;
    }
    else {
        return b;
    }

}

#endif

#ifdef FLOAT128

/*
-------------------------------------------------------------------------------
The pattern for a default generated quadruple-precision NaN.  The `high' and
`low' values hold the most- and least-significant bits, respectively.
-------------------------------------------------------------------------------
*/
#define float128_default_nan_high LIT64( 0xFFFFFFFFFFFFFFFF )
#define float128_default_nan_low  LIT64( 0xFFFFFFFFFFFFFFFF )

/*
-------------------------------------------------------------------------------
Returns 1 if the quadruple-precision floating-point value `a' is a NaN;
otherwise returns 0.
-------------------------------------------------------------------------------
*/
flag float128_is_nan( float128 a )
{

    return
           ( (bits64)LIT64( 0xFFFE000000000000 ) <= (bits64) ( a.high<<1 ) )
        && ( a.low || ( a.high & LIT64( 0x0000FFFFFFFFFFFF ) ) );

}

/*
-------------------------------------------------------------------------------
Returns 1 if the quadruple-precision floating-point value `a' is a
signaling NaN; otherwise returns 0.
-------------------------------------------------------------------------------
*/
flag float128_is_signaling_nan( float128 a )
{

    return
           ( ( ( a.high>>47 ) & 0xFFFF ) == 0xFFFE )
        && ( a.low || ( a.high & LIT64( 0x00007FFFFFFFFFFF ) ) );

}

/*
-------------------------------------------------------------------------------
Returns the result of converting the quadruple-precision floating-point NaN
`a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
exception is raised.
-------------------------------------------------------------------------------
*/
static commonNaNT float128ToCommonNaN( float128 a )
{
    commonNaNT z;

    if ( float128_is_signaling_nan( a ) ) float_raise( float_flag_invalid );
    z.sign = (flag)(a.high>>63);
    shortShift128Left( a.high, a.low, 16, &z.high, &z.low );
    return z;

}

/*
-------------------------------------------------------------------------------
Returns the result of converting the canonical NaN `a' to the quadruple-
precision floating-point format.
-------------------------------------------------------------------------------
*/
static float128 commonNaNToFloat128( commonNaNT a )
{
    float128 z;

    shift128Right( a.high, a.low, 16, &z.high, &z.low );
    z.high |= ( ( (bits64) a.sign )<<63 ) | LIT64( 0x7FFF800000000000 );
    return z;

}

/*
-------------------------------------------------------------------------------
Takes two quadruple-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.
-------------------------------------------------------------------------------
*/
static float128 propagateFloat128NaN( float128 a, float128 b )
{
    flag aIsNaN, aIsSignalingNaN, bIsNaN, bIsSignalingNaN;

    aIsNaN = float128_is_nan( a );
    aIsSignalingNaN = float128_is_signaling_nan( a );
    bIsNaN = float128_is_nan( b );
    bIsSignalingNaN = float128_is_signaling_nan( b );
    a.high |= LIT64( 0x0000800000000000 );
    b.high |= LIT64( 0x0000800000000000 );
    if ( aIsSignalingNaN | bIsSignalingNaN ) float_raise( float_flag_invalid );
    if ( aIsNaN ) {
        return ( aIsSignalingNaN & bIsNaN ) ? b : a;
    }
    else {
        return b;
    }

}

#endif