patch-2.4.20 linux-2.4.20/arch/parisc/math-emu/sfsub.c

• Lines: 522
• Date: Thu Nov 28 15:53:10 2002
• Orig file: linux-2.4.19/arch/parisc/math-emu/sfsub.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/parisc/math-emu/sfsub.c linux-2.4.20/arch/parisc/math-emu/sfsub.c
@@ -0,0 +1,521 @@
+/*
+ * Linux/PA-RISC Project (http://www.parisc-linux.org/)
+ *
+ * Floating-point emulation code
+ *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
+ *
+ *    This program is free software; you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation; either version 2, or (at your option)
+ *    any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program; if not, write to the Free Software
+ *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+/*
+ * BEGIN_DESC
+ *
+ *  File:
+ *	@(#)	pa/spmath/sfsub.c		$Revision: 1.1 $
+ *
+ *  Purpose:
+ *	Single_subtract: subtract two single precision values.
+ *
+ *  External Interfaces:
+ *	sgl_fsub(leftptr, rightptr, dstptr, status)
+ *
+ *  Internal Interfaces:
+ *
+ *  Theory:
+ *	<<please update with a overview of the operation of this file>>
+ *
+ * END_DESC
+*/
+
+
+#include "float.h"
+#include "sgl_float.h"
+
+/*
+ * Single_subtract: subtract two single precision values.
+ */
+int
+sgl_fsub(
+	    sgl_floating_point *leftptr,
+	    sgl_floating_point *rightptr,
+	    sgl_floating_point *dstptr,
+	    unsigned int *status)
+    {
+    register unsigned int left, right, result, extent;
+    register unsigned int signless_upper_left, signless_upper_right, save;
+    
+    register int result_exponent, right_exponent, diff_exponent;
+    register int sign_save, jumpsize;
+    register boolean inexact = FALSE, underflowtrap;
+        
+    /* Create local copies of the numbers */
+    left = *leftptr;
+    right = *rightptr;
+
+    /* A zero "save" helps discover equal operands (for later),  *
+     * and is used in swapping operands (if needed).             */
+    Sgl_xortointp1(left,right,/*to*/save);
+
+    /*
+     * check first operand for NaN's or infinity
+     */
+    if ((result_exponent = Sgl_exponent(left)) == SGL_INFINITY_EXPONENT)
+	{
+	if (Sgl_iszero_mantissa(left)) 
+	    {
+	    if (Sgl_isnotnan(right)) 
+		{
+		if (Sgl_isinfinity(right) && save==0) 
+		    {
+		    /* 
+		     * invalid since operands are same signed infinity's
+		     */
+		    if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
+                    Set_invalidflag();
+                    Sgl_makequietnan(result);
+		    *dstptr = result;
+		    return(NOEXCEPTION);
+		    }
+		/*
+	 	 * return infinity
+	 	 */
+		*dstptr = left;
+		return(NOEXCEPTION);
+		}
+	    }
+	else 
+	    {
+            /*
+             * is NaN; signaling or quiet?
+             */
+            if (Sgl_isone_signaling(left)) 
+		{
+               	/* trap if INVALIDTRAP enabled */
+		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
+        	/* make NaN quiet */
+        	Set_invalidflag();
+        	Sgl_set_quiet(left);
+        	}
+	    /* 
+	     * is second operand a signaling NaN? 
+	     */
+	    else if (Sgl_is_signalingnan(right)) 
+		{
+        	/* trap if INVALIDTRAP enabled */
+               	if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
+		/* make NaN quiet */
+		Set_invalidflag();
+		Sgl_set_quiet(right);
+		*dstptr = right;
+		return(NOEXCEPTION);
+		}
+	    /*
+ 	     * return quiet NaN
+ 	     */
+ 	    *dstptr = left;
+ 	    return(NOEXCEPTION);
+	    }
+	} /* End left NaN or Infinity processing */
+    /*
+     * check second operand for NaN's or infinity
+     */
+    if (Sgl_isinfinity_exponent(right)) 
+	{
+	if (Sgl_iszero_mantissa(right)) 
+	    {
+	    /* return infinity */
+	    Sgl_invert_sign(right);
+	    *dstptr = right;
+	    return(NOEXCEPTION);
+	    }
+        /*
+         * is NaN; signaling or quiet?
+         */
+        if (Sgl_isone_signaling(right)) 
+	    {
+            /* trap if INVALIDTRAP enabled */
+	    if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
+	    /* make NaN quiet */
+	    Set_invalidflag();
+	    Sgl_set_quiet(right);
+	    }
+	/*
+	 * return quiet NaN
+ 	 */
+	*dstptr = right;
+	return(NOEXCEPTION);
+    	} /* End right NaN or Infinity processing */
+
+    /* Invariant: Must be dealing with finite numbers */
+
+    /* Compare operands by removing the sign */
+    Sgl_copytoint_exponentmantissa(left,signless_upper_left);
+    Sgl_copytoint_exponentmantissa(right,signless_upper_right);
+
+    /* sign difference selects sub or add operation. */
+    if(Sgl_ismagnitudeless(signless_upper_left,signless_upper_right))
+	{
+	/* Set the left operand to the larger one by XOR swap *
+	 *  First finish the first word using "save"          */
+	Sgl_xorfromintp1(save,right,/*to*/right);
+	Sgl_xorfromintp1(save,left,/*to*/left);
+	result_exponent = Sgl_exponent(left);
+	Sgl_invert_sign(left);
+	}
+    /* Invariant:  left is not smaller than right. */ 
+
+    if((right_exponent = Sgl_exponent(right)) == 0)
+        {
+	/* Denormalized operands.  First look for zeroes */
+	if(Sgl_iszero_mantissa(right)) 
+	    {
+	    /* right is zero */
+	    if(Sgl_iszero_exponentmantissa(left))
+		{
+		/* Both operands are zeros */
+		Sgl_invert_sign(right);
+		if(Is_rounding_mode(ROUNDMINUS))
+		    {
+		    Sgl_or_signs(left,/*with*/right);
+		    }
+		else
+		    {
+		    Sgl_and_signs(left,/*with*/right);
+		    }
+		}
+	    else 
+		{
+		/* Left is not a zero and must be the result.  Trapped
+		 * underflows are signaled if left is denormalized.  Result
+		 * is always exact. */
+		if( (result_exponent == 0) && Is_underflowtrap_enabled() )
+		    {
+		    /* need to normalize results mantissa */
+	    	    sign_save = Sgl_signextendedsign(left);
+		    Sgl_leftshiftby1(left);
+		    Sgl_normalize(left,result_exponent);
+		    Sgl_set_sign(left,/*using*/sign_save);
+                    Sgl_setwrapped_exponent(left,result_exponent,unfl);
+		    *dstptr = left;
+		    /* inexact = FALSE */
+		    return(UNDERFLOWEXCEPTION);
+		    }
+		}
+	    *dstptr = left;
+	    return(NOEXCEPTION);
+	    }
+
+	/* Neither are zeroes */
+	Sgl_clear_sign(right);	/* Exponent is already cleared */
+	if(result_exponent == 0 )
+	    {
+	    /* Both operands are denormalized.  The result must be exact
+	     * and is simply calculated.  A sum could become normalized and a
+	     * difference could cancel to a true zero. */
+	    if( (/*signed*/int) save >= 0 )
+		{
+		Sgl_subtract(left,/*minus*/right,/*into*/result);
+		if(Sgl_iszero_mantissa(result))
+		    {
+		    if(Is_rounding_mode(ROUNDMINUS))
+			{
+			Sgl_setone_sign(result);
+			}
+		    else
+			{
+			Sgl_setzero_sign(result);
+			}
+		    *dstptr = result;
+		    return(NOEXCEPTION);
+		    }
+		}
+	    else
+		{
+		Sgl_addition(left,right,/*into*/result);
+		if(Sgl_isone_hidden(result))
+		    {
+		    *dstptr = result;
+		    return(NOEXCEPTION);
+		    }
+		}
+	    if(Is_underflowtrap_enabled())
+		{
+		/* need to normalize result */
+	    	sign_save = Sgl_signextendedsign(result);
+		Sgl_leftshiftby1(result);
+		Sgl_normalize(result,result_exponent);
+		Sgl_set_sign(result,/*using*/sign_save);
+                Sgl_setwrapped_exponent(result,result_exponent,unfl);
+		*dstptr = result;
+		/* inexact = FALSE */
+		return(UNDERFLOWEXCEPTION);
+		}
+	    *dstptr = result;
+	    return(NOEXCEPTION);
+	    }
+	right_exponent = 1;	/* Set exponent to reflect different bias
+				 * with denomalized numbers. */
+	}
+    else
+	{
+	Sgl_clear_signexponent_set_hidden(right);
+	}
+    Sgl_clear_exponent_set_hidden(left);
+    diff_exponent = result_exponent - right_exponent;
+
+    /* 
+     * Special case alignment of operands that would force alignment 
+     * beyond the extent of the extension.  A further optimization
+     * could special case this but only reduces the path length for this
+     * infrequent case.
+     */
+    if(diff_exponent > SGL_THRESHOLD)
+	{
+	diff_exponent = SGL_THRESHOLD;
+	}
+    
+    /* Align right operand by shifting to right */
+    Sgl_right_align(/*operand*/right,/*shifted by*/diff_exponent,
+      /*and lower to*/extent);
+
+    /* Treat sum and difference of the operands separately. */
+    if( (/*signed*/int) save >= 0 )
+	{
+	/*
+	 * Difference of the two operands.  Their can be no overflow.  A
+	 * borrow can occur out of the hidden bit and force a post
+	 * normalization phase.
+	 */
+	Sgl_subtract_withextension(left,/*minus*/right,/*with*/extent,/*into*/result);
+	if(Sgl_iszero_hidden(result))
+	    {
+	    /* Handle normalization */
+	    /* A straight foward algorithm would now shift the result
+	     * and extension left until the hidden bit becomes one.  Not
+	     * all of the extension bits need participate in the shift.
+	     * Only the two most significant bits (round and guard) are
+	     * needed.  If only a single shift is needed then the guard
+	     * bit becomes a significant low order bit and the extension
+	     * must participate in the rounding.  If more than a single 
+	     * shift is needed, then all bits to the right of the guard 
+	     * bit are zeros, and the guard bit may or may not be zero. */
+	    sign_save = Sgl_signextendedsign(result);
+            Sgl_leftshiftby1_withextent(result,extent,result);
+
+            /* Need to check for a zero result.  The sign and exponent
+	     * fields have already been zeroed.  The more efficient test
+	     * of the full object can be used.
+	     */
+    	    if(Sgl_iszero(result))
+		/* Must have been "x-x" or "x+(-x)". */
+		{
+		if(Is_rounding_mode(ROUNDMINUS)) Sgl_setone_sign(result);
+		*dstptr = result;
+		return(NOEXCEPTION);
+		}
+	    result_exponent--;
+	    /* Look to see if normalization is finished. */
+	    if(Sgl_isone_hidden(result))
+		{
+		if(result_exponent==0)
+		    {
+		    /* Denormalized, exponent should be zero.  Left operand *
+ 		     * was normalized, so extent (guard, round) was zero    */
+		    goto underflow;
+		    }
+		else
+		    {
+		    /* No further normalization is needed. */
+		    Sgl_set_sign(result,/*using*/sign_save);
+	    	    Ext_leftshiftby1(extent);
+		    goto round;
+		    }
+		}
+
+	    /* Check for denormalized, exponent should be zero.  Left    *
+	     * operand was normalized, so extent (guard, round) was zero */
+	    if(!(underflowtrap = Is_underflowtrap_enabled()) &&
+	       result_exponent==0) goto underflow;
+
+	    /* Shift extension to complete one bit of normalization and
+	     * update exponent. */
+	    Ext_leftshiftby1(extent);
+
+	    /* Discover first one bit to determine shift amount.  Use a
+	     * modified binary search.  We have already shifted the result
+	     * one position right and still not found a one so the remainder
+	     * of the extension must be zero and simplifies rounding. */
+	    /* Scan bytes */
+	    while(Sgl_iszero_hiddenhigh7mantissa(result))
+		{
+		Sgl_leftshiftby8(result);
+		if((result_exponent -= 8) <= 0  && !underflowtrap)
+		    goto underflow;
+		}
+	    /* Now narrow it down to the nibble */
+	    if(Sgl_iszero_hiddenhigh3mantissa(result))
+		{
+		/* The lower nibble contains the normalizing one */
+		Sgl_leftshiftby4(result);
+		if((result_exponent -= 4) <= 0 && !underflowtrap)
+		    goto underflow;
+		}
+	    /* Select case were first bit is set (already normalized)
+	     * otherwise select the proper shift. */
+	    if((jumpsize = Sgl_hiddenhigh3mantissa(result)) > 7)
+		{
+		/* Already normalized */
+		if(result_exponent <= 0) goto underflow;
+		Sgl_set_sign(result,/*using*/sign_save);
+		Sgl_set_exponent(result,/*using*/result_exponent);
+		*dstptr = result;
+		return(NOEXCEPTION);
+		}
+	    Sgl_sethigh4bits(result,/*using*/sign_save);
+	    switch(jumpsize) 
+		{
+		case 1:
+		    {
+		    Sgl_leftshiftby3(result);
+		    result_exponent -= 3;
+		    break;
+		    }
+		case 2:
+		case 3:
+		    {
+		    Sgl_leftshiftby2(result);
+		    result_exponent -= 2;
+		    break;
+		    }
+		case 4:
+		case 5:
+		case 6:
+		case 7:
+		    {
+		    Sgl_leftshiftby1(result);
+		    result_exponent -= 1;
+		    break;
+		    }
+		}
+	    if(result_exponent > 0) 
+		{
+		Sgl_set_exponent(result,/*using*/result_exponent);
+		*dstptr = result;	/* Sign bit is already set */
+		return(NOEXCEPTION);
+		}
+	    /* Fixup potential underflows */
+	  underflow:
+	    if(Is_underflowtrap_enabled())
+		{
+		Sgl_set_sign(result,sign_save);
+                Sgl_setwrapped_exponent(result,result_exponent,unfl);
+		*dstptr = result;
+		/* inexact = FALSE */
+		return(UNDERFLOWEXCEPTION);
+		}
+	    /*
+	     * Since we cannot get an inexact denormalized result,
+	     * we can now return.
+	     */
+	    Sgl_right_align(result,/*by*/(1-result_exponent),extent);
+	    Sgl_clear_signexponent(result);
+	    Sgl_set_sign(result,sign_save);
+	    *dstptr = result;
+	    return(NOEXCEPTION);
+	    } /* end if(hidden...)... */
+	/* Fall through and round */
+	} /* end if(save >= 0)... */
+    else 
+	{
+	/* Add magnitudes */
+	Sgl_addition(left,right,/*to*/result);
+	if(Sgl_isone_hiddenoverflow(result))
+	    {
+	    /* Prenormalization required. */
+	    Sgl_rightshiftby1_withextent(result,extent,extent);
+	    Sgl_arithrightshiftby1(result);
+	    result_exponent++;
+	    } /* end if hiddenoverflow... */
+	} /* end else ...sub magnitudes... */
+    
+    /* Round the result.  If the extension is all zeros,then the result is
+     * exact.  Otherwise round in the correct direction.  No underflow is
+     * possible. If a postnormalization is necessary, then the mantissa is
+     * all zeros so no shift is needed. */
+  round:
+    if(Ext_isnotzero(extent))
+	{
+	inexact = TRUE;
+	switch(Rounding_mode())
+	    {
+	    case ROUNDNEAREST: /* The default. */
+	    if(Ext_isone_sign(extent))
+		{
+		/* at least 1/2 ulp */
+		if(Ext_isnotzero_lower(extent)  ||
+		  Sgl_isone_lowmantissa(result))
+		    {
+		    /* either exactly half way and odd or more than 1/2ulp */
+		    Sgl_increment(result);
+		    }
+		}
+	    break;
+
+	    case ROUNDPLUS:
+	    if(Sgl_iszero_sign(result))
+		{
+		/* Round up positive results */
+		Sgl_increment(result);
+		}
+	    break;
+	    
+	    case ROUNDMINUS:
+	    if(Sgl_isone_sign(result))
+		{
+		/* Round down negative results */
+		Sgl_increment(result);
+		}
+	    
+	    case ROUNDZERO:;
+	    /* truncate is simple */
+	    } /* end switch... */
+	if(Sgl_isone_hiddenoverflow(result)) result_exponent++;
+	}
+    if(result_exponent == SGL_INFINITY_EXPONENT)
+        {
+        /* Overflow */
+        if(Is_overflowtrap_enabled())
+	    {
+	    Sgl_setwrapped_exponent(result,result_exponent,ovfl);
+	    *dstptr = result;
+	    if (inexact)
+		if (Is_inexacttrap_enabled())
+		    return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
+		else Set_inexactflag();
+	    return(OVERFLOWEXCEPTION);
+	    }
+        else
+	    {
+	    Set_overflowflag();
+	    inexact = TRUE;
+	    Sgl_setoverflow(result);
+	    }
+	}
+    else Sgl_set_exponent(result,result_exponent);
+    *dstptr = result;
+    if(inexact) 
+	if(Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
+	else Set_inexactflag();
+    return(NOEXCEPTION);
+    }