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

• Lines: 2656
• Date: Thu Nov 28 15:53:10 2002
• Orig file: linux-2.4.19/arch/parisc/math-emu/fmpyfadd.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/parisc/math-emu/fmpyfadd.c linux-2.4.20/arch/parisc/math-emu/fmpyfadd.c
@@ -0,0 +1,2655 @@
+/*
+ * 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/fmpyfadd.c		$Revision: 1.1 $
+ *
+ *  Purpose:
+ *	Double Floating-point Multiply Fused Add
+ *	Double Floating-point Multiply Negate Fused Add
+ *	Single Floating-point Multiply Fused Add
+ *	Single Floating-point Multiply Negate Fused Add
+ *
+ *  External Interfaces:
+ *	dbl_fmpyfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
+ *	dbl_fmpynfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
+ *	sgl_fmpyfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
+ *	sgl_fmpynfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
+ *
+ *  Internal Interfaces:
+ *
+ *  Theory:
+ *	<<please update with a overview of the operation of this file>>
+ *
+ * END_DESC
+*/
+
+
+#include "float.h"
+#include "sgl_float.h"
+#include "dbl_float.h"
+
+
+/*
+ *  Double Floating-point Multiply Fused Add
+ */
+
+int
+dbl_fmpyfadd(
+	    dbl_floating_point *src1ptr,
+	    dbl_floating_point *src2ptr,
+	    dbl_floating_point *src3ptr,
+	    unsigned int *status,
+	    dbl_floating_point *dstptr)
+{
+	unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2, opnd3p1, opnd3p2;
+	register unsigned int tmpresp1, tmpresp2, tmpresp3, tmpresp4;
+	unsigned int rightp1, rightp2, rightp3, rightp4;
+	unsigned int resultp1, resultp2 = 0, resultp3 = 0, resultp4 = 0;
+	register int mpy_exponent, add_exponent, count;
+	boolean inexact = FALSE, is_tiny = FALSE;
+
+	unsigned int signlessleft1, signlessright1, save;
+	register int result_exponent, diff_exponent;
+	int sign_save, jumpsize;
+	
+	Dbl_copyfromptr(src1ptr,opnd1p1,opnd1p2);
+	Dbl_copyfromptr(src2ptr,opnd2p1,opnd2p2);
+	Dbl_copyfromptr(src3ptr,opnd3p1,opnd3p2);
+
+	/* 
+	 * set sign bit of result of multiply
+	 */
+	if (Dbl_sign(opnd1p1) ^ Dbl_sign(opnd2p1)) 
+		Dbl_setnegativezerop1(resultp1); 
+	else Dbl_setzerop1(resultp1);
+
+	/*
+	 * Generate multiply exponent 
+	 */
+	mpy_exponent = Dbl_exponent(opnd1p1) + Dbl_exponent(opnd2p1) - DBL_BIAS;
+
+	/*
+	 * check first operand for NaN's or infinity
+	 */
+	if (Dbl_isinfinity_exponent(opnd1p1)) {
+		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
+			if (Dbl_isnotnan(opnd2p1,opnd2p2) &&
+			    Dbl_isnotnan(opnd3p1,opnd3p2)) {
+				if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
+					/* 
+					 * invalid since operands are infinity 
+					 * and zero 
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Dbl_makequietnan(resultp1,resultp2);
+					Dbl_copytoptr(resultp1,resultp2,dstptr);
+					return(NOEXCEPTION);
+				}
+				/*
+				 * Check third operand for infinity with a
+				 *  sign opposite of the multiply result
+				 */
+				if (Dbl_isinfinity(opnd3p1,opnd3p2) &&
+				    (Dbl_sign(resultp1) ^ Dbl_sign(opnd3p1))) {
+					/* 
+					 * invalid since attempting a magnitude
+					 * subtraction of infinities
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Dbl_makequietnan(resultp1,resultp2);
+					Dbl_copytoptr(resultp1,resultp2,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+			 	 * return infinity
+			 	 */
+				Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
+				Dbl_copytoptr(resultp1,resultp2,dstptr);
+				return(NOEXCEPTION);
+			}
+		}
+		else {
+			/*
+		 	 * is NaN; signaling or quiet?
+		 	 */
+			if (Dbl_isone_signaling(opnd1p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled()) 
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd1p1);
+			}
+			/* 
+			 * is second operand a signaling NaN? 
+			 */
+			else if (Dbl_is_signalingnan(opnd2p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd2p1);
+				Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
+				return(NOEXCEPTION);
+			}
+			/* 
+			 * is third operand a signaling NaN? 
+			 */
+			else if (Dbl_is_signalingnan(opnd3p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd3p1);
+				Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+				return(NOEXCEPTION);
+			}
+			/*
+		 	 * return quiet NaN
+		 	 */
+			Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
+			return(NOEXCEPTION);
+		}
+	}
+
+	/*
+	 * check second operand for NaN's or infinity
+	 */
+	if (Dbl_isinfinity_exponent(opnd2p1)) {
+		if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
+			if (Dbl_isnotnan(opnd3p1,opnd3p2)) {
+				if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
+					/* 
+					 * invalid since multiply operands are
+					 * zero & infinity
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Dbl_makequietnan(opnd2p1,opnd2p2);
+					Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+				 * Check third operand for infinity with a
+				 *  sign opposite of the multiply result
+				 */
+				if (Dbl_isinfinity(opnd3p1,opnd3p2) &&
+				    (Dbl_sign(resultp1) ^ Dbl_sign(opnd3p1))) {
+					/* 
+					 * invalid since attempting a magnitude
+					 * subtraction of infinities
+					 */
+					if (Is_invalidtrap_enabled())
+				       		return(OPC_2E_INVALIDEXCEPTION);
+				       	Set_invalidflag();
+				       	Dbl_makequietnan(resultp1,resultp2);
+					Dbl_copytoptr(resultp1,resultp2,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+				 * return infinity
+				 */
+				Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
+				Dbl_copytoptr(resultp1,resultp2,dstptr);
+				return(NOEXCEPTION);
+			}
+		}
+		else {
+			/*
+			 * is NaN; signaling or quiet?
+			 */
+			if (Dbl_isone_signaling(opnd2p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+					return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd2p1);
+			}
+			/* 
+			 * is third operand a signaling NaN? 
+			 */
+			else if (Dbl_is_signalingnan(opnd3p1)) {
+			       	/* trap if INVALIDTRAP enabled */
+			       	if (Is_invalidtrap_enabled())
+				   		return(OPC_2E_INVALIDEXCEPTION);
+			       	/* make NaN quiet */
+			       	Set_invalidflag();
+			       	Dbl_set_quiet(opnd3p1);
+				Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+		       		return(NOEXCEPTION);
+			}
+			/*
+			 * return quiet NaN
+			 */
+			Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
+			return(NOEXCEPTION);
+		}
+	}
+
+	/*
+	 * check third operand for NaN's or infinity
+	 */
+	if (Dbl_isinfinity_exponent(opnd3p1)) {
+		if (Dbl_iszero_mantissa(opnd3p1,opnd3p2)) {
+			/* return infinity */
+			Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+			return(NOEXCEPTION);
+		} else {
+			/*
+			 * is NaN; signaling or quiet?
+			 */
+			if (Dbl_isone_signaling(opnd3p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+					return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd3p1);
+			}
+			/*
+			 * return quiet NaN
+ 			 */
+			Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+			return(NOEXCEPTION);
+		}
+    	}
+
+	/*
+	 * Generate multiply mantissa
+	 */
+	if (Dbl_isnotzero_exponent(opnd1p1)) {
+		/* set hidden bit */
+		Dbl_clear_signexponent_set_hidden(opnd1p1);
+	}
+	else {
+		/* check for zero */
+		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
+			/*
+			 * Perform the add opnd3 with zero here.
+			 */
+			if (Dbl_iszero_exponentmantissa(opnd3p1,opnd3p2)) {
+				if (Is_rounding_mode(ROUNDMINUS)) {
+					Dbl_or_signs(opnd3p1,resultp1);
+				} else {
+					Dbl_and_signs(opnd3p1,resultp1);
+				}
+			}
+			/*
+			 * Now let's check for trapped underflow case.
+			 */
+			else if (Dbl_iszero_exponent(opnd3p1) &&
+			         Is_underflowtrap_enabled()) {
+                    		/* need to normalize results mantissa */
+                    		sign_save = Dbl_signextendedsign(opnd3p1);
+				result_exponent = 0;
+                    		Dbl_leftshiftby1(opnd3p1,opnd3p2);
+                    		Dbl_normalize(opnd3p1,opnd3p2,result_exponent);
+                    		Dbl_set_sign(opnd3p1,/*using*/sign_save);
+                    		Dbl_setwrapped_exponent(opnd3p1,result_exponent,
+							unfl);
+                    		Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+                    		/* inexact = FALSE */
+                    		return(OPC_2E_UNDERFLOWEXCEPTION);
+			}
+			Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+			return(NOEXCEPTION);
+		}
+		/* is denormalized, adjust exponent */
+		Dbl_clear_signexponent(opnd1p1);
+		Dbl_leftshiftby1(opnd1p1,opnd1p2);
+		Dbl_normalize(opnd1p1,opnd1p2,mpy_exponent);
+	}
+	/* opnd2 needs to have hidden bit set with msb in hidden bit */
+	if (Dbl_isnotzero_exponent(opnd2p1)) {
+		Dbl_clear_signexponent_set_hidden(opnd2p1);
+	}
+	else {
+		/* check for zero */
+		if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
+			/*
+			 * Perform the add opnd3 with zero here.
+			 */
+			if (Dbl_iszero_exponentmantissa(opnd3p1,opnd3p2)) {
+				if (Is_rounding_mode(ROUNDMINUS)) {
+					Dbl_or_signs(opnd3p1,resultp1);
+				} else {
+					Dbl_and_signs(opnd3p1,resultp1);
+				}
+			}
+			/*
+			 * Now let's check for trapped underflow case.
+			 */
+			else if (Dbl_iszero_exponent(opnd3p1) &&
+			    Is_underflowtrap_enabled()) {
+                    		/* need to normalize results mantissa */
+                    		sign_save = Dbl_signextendedsign(opnd3p1);
+				result_exponent = 0;
+                    		Dbl_leftshiftby1(opnd3p1,opnd3p2);
+                    		Dbl_normalize(opnd3p1,opnd3p2,result_exponent);
+                    		Dbl_set_sign(opnd3p1,/*using*/sign_save);
+                    		Dbl_setwrapped_exponent(opnd3p1,result_exponent,
+							unfl);
+                    		Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+                    		/* inexact = FALSE */
+				return(OPC_2E_UNDERFLOWEXCEPTION);
+			}
+			Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+			return(NOEXCEPTION);
+		}
+		/* is denormalized; want to normalize */
+		Dbl_clear_signexponent(opnd2p1);
+		Dbl_leftshiftby1(opnd2p1,opnd2p2);
+		Dbl_normalize(opnd2p1,opnd2p2,mpy_exponent);
+	}
+
+	/* Multiply the first two source mantissas together */
+
+	/* 
+	 * The intermediate result will be kept in tmpres,
+	 * which needs enough room for 106 bits of mantissa,
+	 * so lets call it a Double extended.
+	 */
+	Dblext_setzero(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
+
+	/* 
+	 * Four bits at a time are inspected in each loop, and a 
+	 * simple shift and add multiply algorithm is used. 
+	 */ 
+	for (count = DBL_P-1; count >= 0; count -= 4) {
+		Dblext_rightshiftby4(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
+		if (Dbit28p2(opnd1p2)) {
+	 		/* Fourword_add should be an ADD followed by 3 ADDC's */
+			Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4, 
+			 opnd2p1<<3 | opnd2p2>>29, opnd2p2<<3, 0, 0);
+		}
+		if (Dbit29p2(opnd1p2)) {
+			Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
+			 opnd2p1<<2 | opnd2p2>>30, opnd2p2<<2, 0, 0);
+		}
+		if (Dbit30p2(opnd1p2)) {
+			Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
+			 opnd2p1<<1 | opnd2p2>>31, opnd2p2<<1, 0, 0);
+		}
+		if (Dbit31p2(opnd1p2)) {
+			Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
+			 opnd2p1, opnd2p2, 0, 0);
+		}
+		Dbl_rightshiftby4(opnd1p1,opnd1p2);
+	}
+	if (Is_dexthiddenoverflow(tmpresp1)) {
+		/* result mantissa >= 2 (mantissa overflow) */
+		mpy_exponent++;
+		Dblext_rightshiftby1(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
+	}
+
+	/*
+	 * Restore the sign of the mpy result which was saved in resultp1.
+	 * The exponent will continue to be kept in mpy_exponent.
+	 */
+	Dblext_set_sign(tmpresp1,Dbl_sign(resultp1));
+
+	/* 
+	 * No rounding is required, since the result of the multiply
+	 * is exact in the extended format.
+	 */
+
+	/*
+	 * Now we are ready to perform the add portion of the operation.
+	 *
+	 * The exponents need to be kept as integers for now, since the
+	 * multiply result might not fit into the exponent field.  We
+	 * can't overflow or underflow because of this yet, since the
+	 * add could bring the final result back into range.
+	 */
+	add_exponent = Dbl_exponent(opnd3p1);
+
+	/*
+	 * Check for denormalized or zero add operand.
+	 */
+	if (add_exponent == 0) {
+		/* check for zero */
+		if (Dbl_iszero_mantissa(opnd3p1,opnd3p2)) {
+			/* right is zero */
+			/* Left can't be zero and must be result.
+			 *
+			 * The final result is now in tmpres and mpy_exponent,
+			 * and needs to be rounded and squeezed back into
+			 * double precision format from double extended.
+			 */
+			result_exponent = mpy_exponent;
+			Dblext_copy(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
+				resultp1,resultp2,resultp3,resultp4);
+			sign_save = Dbl_signextendedsign(resultp1);/*save sign*/
+			goto round;
+		}
+
+		/* 
+		 * Neither are zeroes.  
+		 * Adjust exponent and normalize add operand.
+		 */
+		sign_save = Dbl_signextendedsign(opnd3p1);	/* save sign */
+		Dbl_clear_signexponent(opnd3p1);
+		Dbl_leftshiftby1(opnd3p1,opnd3p2);
+		Dbl_normalize(opnd3p1,opnd3p2,add_exponent);
+		Dbl_set_sign(opnd3p1,sign_save);	/* restore sign */
+	} else {
+		Dbl_clear_exponent_set_hidden(opnd3p1);
+	}
+	/*
+	 * Copy opnd3 to the double extended variable called right.
+	 */
+	Dbl_copyto_dblext(opnd3p1,opnd3p2,rightp1,rightp2,rightp3,rightp4);
+
+	/*
+	 * A zero "save" helps discover equal operands (for later),
+	 * and is used in swapping operands (if needed).
+	 */
+	Dblext_xortointp1(tmpresp1,rightp1,/*to*/save);
+
+	/*
+	 * Compare magnitude of operands.
+	 */
+	Dblext_copytoint_exponentmantissap1(tmpresp1,signlessleft1);
+	Dblext_copytoint_exponentmantissap1(rightp1,signlessright1);
+	if (mpy_exponent < add_exponent || mpy_exponent == add_exponent &&
+	    Dblext_ismagnitudeless(tmpresp2,rightp2,signlessleft1,signlessright1)){
+		/*
+		 * Set the left operand to the larger one by XOR swap.
+		 * First finish the first word "save".
+		 */
+		Dblext_xorfromintp1(save,rightp1,/*to*/rightp1);
+		Dblext_xorfromintp1(save,tmpresp1,/*to*/tmpresp1);
+		Dblext_swap_lower(tmpresp2,tmpresp3,tmpresp4,
+			rightp2,rightp3,rightp4);
+		/* also setup exponents used in rest of routine */
+		diff_exponent = add_exponent - mpy_exponent;
+		result_exponent = add_exponent;
+	} else {
+		/* also setup exponents used in rest of routine */
+		diff_exponent = mpy_exponent - add_exponent;
+		result_exponent = mpy_exponent;
+	}
+	/* Invariant: left is not smaller than right. */
+
+	/*
+	 * 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 > DBLEXT_THRESHOLD) {
+		diff_exponent = DBLEXT_THRESHOLD;
+	}
+
+	/* Align right operand by shifting it to the right */
+	Dblext_clear_sign(rightp1);
+	Dblext_right_align(rightp1,rightp2,rightp3,rightp4,
+		/*shifted by*/diff_exponent);
+	
+	/* Treat sum and difference of the operands separately. */
+	if ((int)save < 0) {
+		/*
+		 * Difference of the two operands.  Overflow can occur if the
+		 * multiply overflowed.  A borrow can occur out of the hidden
+		 * bit and force a post normalization phase.
+		 */
+		Dblext_subtract(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
+			rightp1,rightp2,rightp3,rightp4,
+			resultp1,resultp2,resultp3,resultp4);
+		sign_save = Dbl_signextendedsign(resultp1);
+		if (Dbl_iszero_hidden(resultp1)) {
+			/* 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. */
+			Dblext_leftshiftby1(resultp1,resultp2,resultp3,
+				resultp4);
+
+			/* 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(Dblext_iszero(resultp1,resultp2,resultp3,resultp4)){
+				/* Must have been "x-x" or "x+(-x)". */
+				if (Is_rounding_mode(ROUNDMINUS))
+					Dbl_setone_sign(resultp1);
+				Dbl_copytoptr(resultp1,resultp2,dstptr);
+				return(NOEXCEPTION);
+			}
+			result_exponent--;
+
+			/* Look to see if normalization is finished. */
+			if (Dbl_isone_hidden(resultp1)) {
+				/* No further normalization is needed */
+				goto round;
+			}
+
+			/* 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 (Dbl_iszero_hiddenhigh7mantissa(resultp1)) {
+				Dblext_leftshiftby8(resultp1,resultp2,resultp3,resultp4);
+				result_exponent -= 8;
+			}
+			/* Now narrow it down to the nibble */
+			if (Dbl_iszero_hiddenhigh3mantissa(resultp1)) {
+				/* The lower nibble contains the
+				 * normalizing one */
+				Dblext_leftshiftby4(resultp1,resultp2,resultp3,resultp4);
+				result_exponent -= 4;
+			}
+			/* Select case where first bit is set (already
+			 * normalized) otherwise select the proper shift. */
+			jumpsize = Dbl_hiddenhigh3mantissa(resultp1);
+			if (jumpsize <= 7) switch(jumpsize) {
+			case 1:
+				Dblext_leftshiftby3(resultp1,resultp2,resultp3,
+					resultp4);
+				result_exponent -= 3;
+				break;
+			case 2:
+			case 3:
+				Dblext_leftshiftby2(resultp1,resultp2,resultp3,
+					resultp4);
+				result_exponent -= 2;
+				break;
+			case 4:
+			case 5:
+			case 6:
+			case 7:
+				Dblext_leftshiftby1(resultp1,resultp2,resultp3,
+					resultp4);
+				result_exponent -= 1;
+				break;
+			}
+		} /* end if (hidden...)... */
+	/* Fall through and round */
+	} /* end if (save < 0)... */
+	else {
+		/* Add magnitudes */
+		Dblext_addition(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
+			rightp1,rightp2,rightp3,rightp4,
+			/*to*/resultp1,resultp2,resultp3,resultp4);
+		sign_save = Dbl_signextendedsign(resultp1);
+		if (Dbl_isone_hiddenoverflow(resultp1)) {
+	    		/* Prenormalization required. */
+	    		Dblext_arithrightshiftby1(resultp1,resultp2,resultp3,
+				resultp4);
+	    		result_exponent++;
+		} /* end if hiddenoverflow... */
+	} /* end else ...add magnitudes... */
+
+	/* Round the result.  If the extension and lower two words are
+	 * all zeros, then the result is exact.  Otherwise round in the
+	 * correct direction.  Underflow is possible. If a postnormalization
+	 * is necessary, then the mantissa is all zeros so no shift is needed.
+	 */
+  round:
+	if (result_exponent <= 0 && !Is_underflowtrap_enabled()) {
+		Dblext_denormalize(resultp1,resultp2,resultp3,resultp4,
+			result_exponent,is_tiny);
+	}
+	Dbl_set_sign(resultp1,/*using*/sign_save);
+	if (Dblext_isnotzero_mantissap3(resultp3) || 
+	    Dblext_isnotzero_mantissap4(resultp4)) {
+		inexact = TRUE;
+		switch(Rounding_mode()) {
+		case ROUNDNEAREST: /* The default. */
+			if (Dblext_isone_highp3(resultp3)) {
+				/* at least 1/2 ulp */
+				if (Dblext_isnotzero_low31p3(resultp3) ||
+				    Dblext_isnotzero_mantissap4(resultp4) ||
+				    Dblext_isone_lowp2(resultp2)) {
+					/* either exactly half way and odd or
+					 * more than 1/2ulp */
+					Dbl_increment(resultp1,resultp2);
+				}
+			}
+	    		break;
+
+		case ROUNDPLUS:
+	    		if (Dbl_iszero_sign(resultp1)) {
+				/* Round up positive results */
+				Dbl_increment(resultp1,resultp2);
+			}
+			break;
+	    
+		case ROUNDMINUS:
+	    		if (Dbl_isone_sign(resultp1)) {
+				/* Round down negative results */
+				Dbl_increment(resultp1,resultp2);
+			}
+	    
+		case ROUNDZERO:;
+			/* truncate is simple */
+		} /* end switch... */
+		if (Dbl_isone_hiddenoverflow(resultp1)) result_exponent++;
+	}
+	if (result_exponent >= DBL_INFINITY_EXPONENT) {
+                /* trap if OVERFLOWTRAP enabled */
+                if (Is_overflowtrap_enabled()) {
+                        /*
+                         * Adjust bias of result
+                         */
+                        Dbl_setwrapped_exponent(resultp1,result_exponent,ovfl);
+                        Dbl_copytoptr(resultp1,resultp2,dstptr);
+                        if (inexact)
+                            if (Is_inexacttrap_enabled())
+                                return (OPC_2E_OVERFLOWEXCEPTION |
+					OPC_2E_INEXACTEXCEPTION);
+                            else Set_inexactflag();
+                        return (OPC_2E_OVERFLOWEXCEPTION);
+                }
+                inexact = TRUE;
+                Set_overflowflag();
+                /* set result to infinity or largest number */
+                Dbl_setoverflow(resultp1,resultp2);
+
+	} else if (result_exponent <= 0) {	/* underflow case */
+		if (Is_underflowtrap_enabled()) {
+                        /*
+                         * Adjust bias of result
+                         */
+                	Dbl_setwrapped_exponent(resultp1,result_exponent,unfl);
+			Dbl_copytoptr(resultp1,resultp2,dstptr);
+                        if (inexact)
+                            if (Is_inexacttrap_enabled())
+                                return (OPC_2E_UNDERFLOWEXCEPTION |
+					OPC_2E_INEXACTEXCEPTION);
+                            else Set_inexactflag();
+	    		return(OPC_2E_UNDERFLOWEXCEPTION);
+		}
+		else if (inexact && is_tiny) Set_underflowflag();
+	}
+	else Dbl_set_exponent(resultp1,result_exponent);
+	Dbl_copytoptr(resultp1,resultp2,dstptr);
+	if (inexact) 
+		if (Is_inexacttrap_enabled()) return(OPC_2E_INEXACTEXCEPTION);
+		else Set_inexactflag();
+    	return(NOEXCEPTION);
+}
+
+/*
+ *  Double Floating-point Multiply Negate Fused Add
+ */
+
+dbl_fmpynfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
+
+dbl_floating_point *src1ptr, *src2ptr, *src3ptr, *dstptr;
+unsigned int *status;
+{
+	unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2, opnd3p1, opnd3p2;
+	register unsigned int tmpresp1, tmpresp2, tmpresp3, tmpresp4;
+	unsigned int rightp1, rightp2, rightp3, rightp4;
+	unsigned int resultp1, resultp2 = 0, resultp3 = 0, resultp4 = 0;
+	register int mpy_exponent, add_exponent, count;
+	boolean inexact = FALSE, is_tiny = FALSE;
+
+	unsigned int signlessleft1, signlessright1, save;
+	register int result_exponent, diff_exponent;
+	int sign_save, jumpsize;
+	
+	Dbl_copyfromptr(src1ptr,opnd1p1,opnd1p2);
+	Dbl_copyfromptr(src2ptr,opnd2p1,opnd2p2);
+	Dbl_copyfromptr(src3ptr,opnd3p1,opnd3p2);
+
+	/* 
+	 * set sign bit of result of multiply
+	 */
+	if (Dbl_sign(opnd1p1) ^ Dbl_sign(opnd2p1)) 
+		Dbl_setzerop1(resultp1);
+	else
+		Dbl_setnegativezerop1(resultp1); 
+
+	/*
+	 * Generate multiply exponent 
+	 */
+	mpy_exponent = Dbl_exponent(opnd1p1) + Dbl_exponent(opnd2p1) - DBL_BIAS;
+
+	/*
+	 * check first operand for NaN's or infinity
+	 */
+	if (Dbl_isinfinity_exponent(opnd1p1)) {
+		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
+			if (Dbl_isnotnan(opnd2p1,opnd2p2) &&
+			    Dbl_isnotnan(opnd3p1,opnd3p2)) {
+				if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
+					/* 
+					 * invalid since operands are infinity 
+					 * and zero 
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Dbl_makequietnan(resultp1,resultp2);
+					Dbl_copytoptr(resultp1,resultp2,dstptr);
+					return(NOEXCEPTION);
+				}
+				/*
+				 * Check third operand for infinity with a
+				 *  sign opposite of the multiply result
+				 */
+				if (Dbl_isinfinity(opnd3p1,opnd3p2) &&
+				    (Dbl_sign(resultp1) ^ Dbl_sign(opnd3p1))) {
+					/* 
+					 * invalid since attempting a magnitude
+					 * subtraction of infinities
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Dbl_makequietnan(resultp1,resultp2);
+					Dbl_copytoptr(resultp1,resultp2,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+			 	 * return infinity
+			 	 */
+				Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
+				Dbl_copytoptr(resultp1,resultp2,dstptr);
+				return(NOEXCEPTION);
+			}
+		}
+		else {
+			/*
+		 	 * is NaN; signaling or quiet?
+		 	 */
+			if (Dbl_isone_signaling(opnd1p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled()) 
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd1p1);
+			}
+			/* 
+			 * is second operand a signaling NaN? 
+			 */
+			else if (Dbl_is_signalingnan(opnd2p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd2p1);
+				Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
+				return(NOEXCEPTION);
+			}
+			/* 
+			 * is third operand a signaling NaN? 
+			 */
+			else if (Dbl_is_signalingnan(opnd3p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd3p1);
+				Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+				return(NOEXCEPTION);
+			}
+			/*
+		 	 * return quiet NaN
+		 	 */
+			Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
+			return(NOEXCEPTION);
+		}
+	}
+
+	/*
+	 * check second operand for NaN's or infinity
+	 */
+	if (Dbl_isinfinity_exponent(opnd2p1)) {
+		if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
+			if (Dbl_isnotnan(opnd3p1,opnd3p2)) {
+				if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
+					/* 
+					 * invalid since multiply operands are
+					 * zero & infinity
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Dbl_makequietnan(opnd2p1,opnd2p2);
+					Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+				 * Check third operand for infinity with a
+				 *  sign opposite of the multiply result
+				 */
+				if (Dbl_isinfinity(opnd3p1,opnd3p2) &&
+				    (Dbl_sign(resultp1) ^ Dbl_sign(opnd3p1))) {
+					/* 
+					 * invalid since attempting a magnitude
+					 * subtraction of infinities
+					 */
+					if (Is_invalidtrap_enabled())
+				       		return(OPC_2E_INVALIDEXCEPTION);
+				       	Set_invalidflag();
+				       	Dbl_makequietnan(resultp1,resultp2);
+					Dbl_copytoptr(resultp1,resultp2,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+				 * return infinity
+				 */
+				Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
+				Dbl_copytoptr(resultp1,resultp2,dstptr);
+				return(NOEXCEPTION);
+			}
+		}
+		else {
+			/*
+			 * is NaN; signaling or quiet?
+			 */
+			if (Dbl_isone_signaling(opnd2p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+					return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd2p1);
+			}
+			/* 
+			 * is third operand a signaling NaN? 
+			 */
+			else if (Dbl_is_signalingnan(opnd3p1)) {
+			       	/* trap if INVALIDTRAP enabled */
+			       	if (Is_invalidtrap_enabled())
+				   		return(OPC_2E_INVALIDEXCEPTION);
+			       	/* make NaN quiet */
+			       	Set_invalidflag();
+			       	Dbl_set_quiet(opnd3p1);
+				Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+		       		return(NOEXCEPTION);
+			}
+			/*
+			 * return quiet NaN
+			 */
+			Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
+			return(NOEXCEPTION);
+		}
+	}
+
+	/*
+	 * check third operand for NaN's or infinity
+	 */
+	if (Dbl_isinfinity_exponent(opnd3p1)) {
+		if (Dbl_iszero_mantissa(opnd3p1,opnd3p2)) {
+			/* return infinity */
+			Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+			return(NOEXCEPTION);
+		} else {
+			/*
+			 * is NaN; signaling or quiet?
+			 */
+			if (Dbl_isone_signaling(opnd3p1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+					return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Dbl_set_quiet(opnd3p1);
+			}
+			/*
+			 * return quiet NaN
+ 			 */
+			Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+			return(NOEXCEPTION);
+		}
+    	}
+
+	/*
+	 * Generate multiply mantissa
+	 */
+	if (Dbl_isnotzero_exponent(opnd1p1)) {
+		/* set hidden bit */
+		Dbl_clear_signexponent_set_hidden(opnd1p1);
+	}
+	else {
+		/* check for zero */
+		if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
+			/*
+			 * Perform the add opnd3 with zero here.
+			 */
+			if (Dbl_iszero_exponentmantissa(opnd3p1,opnd3p2)) {
+				if (Is_rounding_mode(ROUNDMINUS)) {
+					Dbl_or_signs(opnd3p1,resultp1);
+				} else {
+					Dbl_and_signs(opnd3p1,resultp1);
+				}
+			}
+			/*
+			 * Now let's check for trapped underflow case.
+			 */
+			else if (Dbl_iszero_exponent(opnd3p1) &&
+			         Is_underflowtrap_enabled()) {
+                    		/* need to normalize results mantissa */
+                    		sign_save = Dbl_signextendedsign(opnd3p1);
+				result_exponent = 0;
+                    		Dbl_leftshiftby1(opnd3p1,opnd3p2);
+                    		Dbl_normalize(opnd3p1,opnd3p2,result_exponent);
+                    		Dbl_set_sign(opnd3p1,/*using*/sign_save);
+                    		Dbl_setwrapped_exponent(opnd3p1,result_exponent,
+							unfl);
+                    		Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+                    		/* inexact = FALSE */
+                    		return(OPC_2E_UNDERFLOWEXCEPTION);
+			}
+			Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+			return(NOEXCEPTION);
+		}
+		/* is denormalized, adjust exponent */
+		Dbl_clear_signexponent(opnd1p1);
+		Dbl_leftshiftby1(opnd1p1,opnd1p2);
+		Dbl_normalize(opnd1p1,opnd1p2,mpy_exponent);
+	}
+	/* opnd2 needs to have hidden bit set with msb in hidden bit */
+	if (Dbl_isnotzero_exponent(opnd2p1)) {
+		Dbl_clear_signexponent_set_hidden(opnd2p1);
+	}
+	else {
+		/* check for zero */
+		if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
+			/*
+			 * Perform the add opnd3 with zero here.
+			 */
+			if (Dbl_iszero_exponentmantissa(opnd3p1,opnd3p2)) {
+				if (Is_rounding_mode(ROUNDMINUS)) {
+					Dbl_or_signs(opnd3p1,resultp1);
+				} else {
+					Dbl_and_signs(opnd3p1,resultp1);
+				}
+			}
+			/*
+			 * Now let's check for trapped underflow case.
+			 */
+			else if (Dbl_iszero_exponent(opnd3p1) &&
+			    Is_underflowtrap_enabled()) {
+                    		/* need to normalize results mantissa */
+                    		sign_save = Dbl_signextendedsign(opnd3p1);
+				result_exponent = 0;
+                    		Dbl_leftshiftby1(opnd3p1,opnd3p2);
+                    		Dbl_normalize(opnd3p1,opnd3p2,result_exponent);
+                    		Dbl_set_sign(opnd3p1,/*using*/sign_save);
+                    		Dbl_setwrapped_exponent(opnd3p1,result_exponent,
+							unfl);
+                    		Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+                    		/* inexact = FALSE */
+                    		return(OPC_2E_UNDERFLOWEXCEPTION);
+			}
+			Dbl_copytoptr(opnd3p1,opnd3p2,dstptr);
+			return(NOEXCEPTION);
+		}
+		/* is denormalized; want to normalize */
+		Dbl_clear_signexponent(opnd2p1);
+		Dbl_leftshiftby1(opnd2p1,opnd2p2);
+		Dbl_normalize(opnd2p1,opnd2p2,mpy_exponent);
+	}
+
+	/* Multiply the first two source mantissas together */
+
+	/* 
+	 * The intermediate result will be kept in tmpres,
+	 * which needs enough room for 106 bits of mantissa,
+	 * so lets call it a Double extended.
+	 */
+	Dblext_setzero(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
+
+	/* 
+	 * Four bits at a time are inspected in each loop, and a 
+	 * simple shift and add multiply algorithm is used. 
+	 */ 
+	for (count = DBL_P-1; count >= 0; count -= 4) {
+		Dblext_rightshiftby4(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
+		if (Dbit28p2(opnd1p2)) {
+	 		/* Fourword_add should be an ADD followed by 3 ADDC's */
+			Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4, 
+			 opnd2p1<<3 | opnd2p2>>29, opnd2p2<<3, 0, 0);
+		}
+		if (Dbit29p2(opnd1p2)) {
+			Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
+			 opnd2p1<<2 | opnd2p2>>30, opnd2p2<<2, 0, 0);
+		}
+		if (Dbit30p2(opnd1p2)) {
+			Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
+			 opnd2p1<<1 | opnd2p2>>31, opnd2p2<<1, 0, 0);
+		}
+		if (Dbit31p2(opnd1p2)) {
+			Fourword_add(tmpresp1, tmpresp2, tmpresp3, tmpresp4,
+			 opnd2p1, opnd2p2, 0, 0);
+		}
+		Dbl_rightshiftby4(opnd1p1,opnd1p2);
+	}
+	if (Is_dexthiddenoverflow(tmpresp1)) {
+		/* result mantissa >= 2 (mantissa overflow) */
+		mpy_exponent++;
+		Dblext_rightshiftby1(tmpresp1,tmpresp2,tmpresp3,tmpresp4);
+	}
+
+	/*
+	 * Restore the sign of the mpy result which was saved in resultp1.
+	 * The exponent will continue to be kept in mpy_exponent.
+	 */
+	Dblext_set_sign(tmpresp1,Dbl_sign(resultp1));
+
+	/* 
+	 * No rounding is required, since the result of the multiply
+	 * is exact in the extended format.
+	 */
+
+	/*
+	 * Now we are ready to perform the add portion of the operation.
+	 *
+	 * The exponents need to be kept as integers for now, since the
+	 * multiply result might not fit into the exponent field.  We
+	 * can't overflow or underflow because of this yet, since the
+	 * add could bring the final result back into range.
+	 */
+	add_exponent = Dbl_exponent(opnd3p1);
+
+	/*
+	 * Check for denormalized or zero add operand.
+	 */
+	if (add_exponent == 0) {
+		/* check for zero */
+		if (Dbl_iszero_mantissa(opnd3p1,opnd3p2)) {
+			/* right is zero */
+			/* Left can't be zero and must be result.
+			 *
+			 * The final result is now in tmpres and mpy_exponent,
+			 * and needs to be rounded and squeezed back into
+			 * double precision format from double extended.
+			 */
+			result_exponent = mpy_exponent;
+			Dblext_copy(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
+				resultp1,resultp2,resultp3,resultp4);
+			sign_save = Dbl_signextendedsign(resultp1);/*save sign*/
+			goto round;
+		}
+
+		/* 
+		 * Neither are zeroes.  
+		 * Adjust exponent and normalize add operand.
+		 */
+		sign_save = Dbl_signextendedsign(opnd3p1);	/* save sign */
+		Dbl_clear_signexponent(opnd3p1);
+		Dbl_leftshiftby1(opnd3p1,opnd3p2);
+		Dbl_normalize(opnd3p1,opnd3p2,add_exponent);
+		Dbl_set_sign(opnd3p1,sign_save);	/* restore sign */
+	} else {
+		Dbl_clear_exponent_set_hidden(opnd3p1);
+	}
+	/*
+	 * Copy opnd3 to the double extended variable called right.
+	 */
+	Dbl_copyto_dblext(opnd3p1,opnd3p2,rightp1,rightp2,rightp3,rightp4);
+
+	/*
+	 * A zero "save" helps discover equal operands (for later),
+	 * and is used in swapping operands (if needed).
+	 */
+	Dblext_xortointp1(tmpresp1,rightp1,/*to*/save);
+
+	/*
+	 * Compare magnitude of operands.
+	 */
+	Dblext_copytoint_exponentmantissap1(tmpresp1,signlessleft1);
+	Dblext_copytoint_exponentmantissap1(rightp1,signlessright1);
+	if (mpy_exponent < add_exponent || mpy_exponent == add_exponent &&
+	    Dblext_ismagnitudeless(tmpresp2,rightp2,signlessleft1,signlessright1)){
+		/*
+		 * Set the left operand to the larger one by XOR swap.
+		 * First finish the first word "save".
+		 */
+		Dblext_xorfromintp1(save,rightp1,/*to*/rightp1);
+		Dblext_xorfromintp1(save,tmpresp1,/*to*/tmpresp1);
+		Dblext_swap_lower(tmpresp2,tmpresp3,tmpresp4,
+			rightp2,rightp3,rightp4);
+		/* also setup exponents used in rest of routine */
+		diff_exponent = add_exponent - mpy_exponent;
+		result_exponent = add_exponent;
+	} else {
+		/* also setup exponents used in rest of routine */
+		diff_exponent = mpy_exponent - add_exponent;
+		result_exponent = mpy_exponent;
+	}
+	/* Invariant: left is not smaller than right. */
+
+	/*
+	 * 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 > DBLEXT_THRESHOLD) {
+		diff_exponent = DBLEXT_THRESHOLD;
+	}
+
+	/* Align right operand by shifting it to the right */
+	Dblext_clear_sign(rightp1);
+	Dblext_right_align(rightp1,rightp2,rightp3,rightp4,
+		/*shifted by*/diff_exponent);
+	
+	/* Treat sum and difference of the operands separately. */
+	if ((int)save < 0) {
+		/*
+		 * Difference of the two operands.  Overflow can occur if the
+		 * multiply overflowed.  A borrow can occur out of the hidden
+		 * bit and force a post normalization phase.
+		 */
+		Dblext_subtract(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
+			rightp1,rightp2,rightp3,rightp4,
+			resultp1,resultp2,resultp3,resultp4);
+		sign_save = Dbl_signextendedsign(resultp1);
+		if (Dbl_iszero_hidden(resultp1)) {
+			/* 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. */
+			Dblext_leftshiftby1(resultp1,resultp2,resultp3,
+				resultp4);
+
+			/* 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 (Dblext_iszero(resultp1,resultp2,resultp3,resultp4)) {
+				/* Must have been "x-x" or "x+(-x)". */
+				if (Is_rounding_mode(ROUNDMINUS))
+					Dbl_setone_sign(resultp1);
+				Dbl_copytoptr(resultp1,resultp2,dstptr);
+				return(NOEXCEPTION);
+			}
+			result_exponent--;
+
+			/* Look to see if normalization is finished. */
+			if (Dbl_isone_hidden(resultp1)) {
+				/* No further normalization is needed */
+				goto round;
+			}
+
+			/* 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 (Dbl_iszero_hiddenhigh7mantissa(resultp1)) {
+				Dblext_leftshiftby8(resultp1,resultp2,resultp3,resultp4);
+				result_exponent -= 8;
+			}
+			/* Now narrow it down to the nibble */
+			if (Dbl_iszero_hiddenhigh3mantissa(resultp1)) {
+				/* The lower nibble contains the
+				 * normalizing one */
+				Dblext_leftshiftby4(resultp1,resultp2,resultp3,resultp4);
+				result_exponent -= 4;
+			}
+			/* Select case where first bit is set (already
+			 * normalized) otherwise select the proper shift. */
+			jumpsize = Dbl_hiddenhigh3mantissa(resultp1);
+			if (jumpsize <= 7) switch(jumpsize) {
+			case 1:
+				Dblext_leftshiftby3(resultp1,resultp2,resultp3,
+					resultp4);
+				result_exponent -= 3;
+				break;
+			case 2:
+			case 3:
+				Dblext_leftshiftby2(resultp1,resultp2,resultp3,
+					resultp4);
+				result_exponent -= 2;
+				break;
+			case 4:
+			case 5:
+			case 6:
+			case 7:
+				Dblext_leftshiftby1(resultp1,resultp2,resultp3,
+					resultp4);
+				result_exponent -= 1;
+				break;
+			}
+		} /* end if (hidden...)... */
+	/* Fall through and round */
+	} /* end if (save < 0)... */
+	else {
+		/* Add magnitudes */
+		Dblext_addition(tmpresp1,tmpresp2,tmpresp3,tmpresp4,
+			rightp1,rightp2,rightp3,rightp4,
+			/*to*/resultp1,resultp2,resultp3,resultp4);
+		sign_save = Dbl_signextendedsign(resultp1);
+		if (Dbl_isone_hiddenoverflow(resultp1)) {
+	    		/* Prenormalization required. */
+	    		Dblext_arithrightshiftby1(resultp1,resultp2,resultp3,
+				resultp4);
+	    		result_exponent++;
+		} /* end if hiddenoverflow... */
+	} /* end else ...add magnitudes... */
+
+	/* Round the result.  If the extension and lower two words are
+	 * all zeros, then the result is exact.  Otherwise round in the
+	 * correct direction.  Underflow is possible. If a postnormalization
+	 * is necessary, then the mantissa is all zeros so no shift is needed.
+	 */
+  round:
+	if (result_exponent <= 0 && !Is_underflowtrap_enabled()) {
+		Dblext_denormalize(resultp1,resultp2,resultp3,resultp4,
+			result_exponent,is_tiny);
+	}
+	Dbl_set_sign(resultp1,/*using*/sign_save);
+	if (Dblext_isnotzero_mantissap3(resultp3) || 
+	    Dblext_isnotzero_mantissap4(resultp4)) {
+		inexact = TRUE;
+		switch(Rounding_mode()) {
+		case ROUNDNEAREST: /* The default. */
+			if (Dblext_isone_highp3(resultp3)) {
+				/* at least 1/2 ulp */
+				if (Dblext_isnotzero_low31p3(resultp3) ||
+				    Dblext_isnotzero_mantissap4(resultp4) ||
+				    Dblext_isone_lowp2(resultp2)) {
+					/* either exactly half way and odd or
+					 * more than 1/2ulp */
+					Dbl_increment(resultp1,resultp2);
+				}
+			}
+	    		break;
+
+		case ROUNDPLUS:
+	    		if (Dbl_iszero_sign(resultp1)) {
+				/* Round up positive results */
+				Dbl_increment(resultp1,resultp2);
+			}
+			break;
+	    
+		case ROUNDMINUS:
+	    		if (Dbl_isone_sign(resultp1)) {
+				/* Round down negative results */
+				Dbl_increment(resultp1,resultp2);
+			}
+	    
+		case ROUNDZERO:;
+			/* truncate is simple */
+		} /* end switch... */
+		if (Dbl_isone_hiddenoverflow(resultp1)) result_exponent++;
+	}
+	if (result_exponent >= DBL_INFINITY_EXPONENT) {
+		/* Overflow */
+		if (Is_overflowtrap_enabled()) {
+                        /*
+                         * Adjust bias of result
+                         */
+                        Dbl_setwrapped_exponent(resultp1,result_exponent,ovfl);
+                        Dbl_copytoptr(resultp1,resultp2,dstptr);
+                        if (inexact)
+                            if (Is_inexacttrap_enabled())
+                                return (OPC_2E_OVERFLOWEXCEPTION |
+					OPC_2E_INEXACTEXCEPTION);
+                            else Set_inexactflag();
+                        return (OPC_2E_OVERFLOWEXCEPTION);
+		}
+		inexact = TRUE;
+		Set_overflowflag();
+		Dbl_setoverflow(resultp1,resultp2);
+	} else if (result_exponent <= 0) {	/* underflow case */
+		if (Is_underflowtrap_enabled()) {
+                        /*
+                         * Adjust bias of result
+                         */
+                	Dbl_setwrapped_exponent(resultp1,result_exponent,unfl);
+			Dbl_copytoptr(resultp1,resultp2,dstptr);
+                        if (inexact)
+                            if (Is_inexacttrap_enabled())
+                                return (OPC_2E_UNDERFLOWEXCEPTION |
+					OPC_2E_INEXACTEXCEPTION);
+                            else Set_inexactflag();
+	    		return(OPC_2E_UNDERFLOWEXCEPTION);
+		}
+		else if (inexact && is_tiny) Set_underflowflag();
+	}
+	else Dbl_set_exponent(resultp1,result_exponent);
+	Dbl_copytoptr(resultp1,resultp2,dstptr);
+	if (inexact) 
+		if (Is_inexacttrap_enabled()) return(OPC_2E_INEXACTEXCEPTION);
+		else Set_inexactflag();
+    	return(NOEXCEPTION);
+}
+
+/*
+ *  Single Floating-point Multiply Fused Add
+ */
+
+sgl_fmpyfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
+
+sgl_floating_point *src1ptr, *src2ptr, *src3ptr, *dstptr;
+unsigned int *status;
+{
+	unsigned int opnd1, opnd2, opnd3;
+	register unsigned int tmpresp1, tmpresp2;
+	unsigned int rightp1, rightp2;
+	unsigned int resultp1, resultp2 = 0;
+	register int mpy_exponent, add_exponent, count;
+	boolean inexact = FALSE, is_tiny = FALSE;
+
+	unsigned int signlessleft1, signlessright1, save;
+	register int result_exponent, diff_exponent;
+	int sign_save, jumpsize;
+	
+	Sgl_copyfromptr(src1ptr,opnd1);
+	Sgl_copyfromptr(src2ptr,opnd2);
+	Sgl_copyfromptr(src3ptr,opnd3);
+
+	/* 
+	 * set sign bit of result of multiply
+	 */
+	if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) 
+		Sgl_setnegativezero(resultp1); 
+	else Sgl_setzero(resultp1);
+
+	/*
+	 * Generate multiply exponent 
+	 */
+	mpy_exponent = Sgl_exponent(opnd1) + Sgl_exponent(opnd2) - SGL_BIAS;
+
+	/*
+	 * check first operand for NaN's or infinity
+	 */
+	if (Sgl_isinfinity_exponent(opnd1)) {
+		if (Sgl_iszero_mantissa(opnd1)) {
+			if (Sgl_isnotnan(opnd2) && Sgl_isnotnan(opnd3)) {
+				if (Sgl_iszero_exponentmantissa(opnd2)) {
+					/* 
+					 * invalid since operands are infinity 
+					 * and zero 
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Sgl_makequietnan(resultp1);
+					Sgl_copytoptr(resultp1,dstptr);
+					return(NOEXCEPTION);
+				}
+				/*
+				 * Check third operand for infinity with a
+				 *  sign opposite of the multiply result
+				 */
+				if (Sgl_isinfinity(opnd3) &&
+				    (Sgl_sign(resultp1) ^ Sgl_sign(opnd3))) {
+					/* 
+					 * invalid since attempting a magnitude
+					 * subtraction of infinities
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Sgl_makequietnan(resultp1);
+					Sgl_copytoptr(resultp1,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+			 	 * return infinity
+			 	 */
+				Sgl_setinfinity_exponentmantissa(resultp1);
+				Sgl_copytoptr(resultp1,dstptr);
+				return(NOEXCEPTION);
+			}
+		}
+		else {
+			/*
+		 	 * is NaN; signaling or quiet?
+		 	 */
+			if (Sgl_isone_signaling(opnd1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled()) 
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd1);
+			}
+			/* 
+			 * is second operand a signaling NaN? 
+			 */
+			else if (Sgl_is_signalingnan(opnd2)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd2);
+				Sgl_copytoptr(opnd2,dstptr);
+				return(NOEXCEPTION);
+			}
+			/* 
+			 * is third operand a signaling NaN? 
+			 */
+			else if (Sgl_is_signalingnan(opnd3)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd3);
+				Sgl_copytoptr(opnd3,dstptr);
+				return(NOEXCEPTION);
+			}
+			/*
+		 	 * return quiet NaN
+		 	 */
+			Sgl_copytoptr(opnd1,dstptr);
+			return(NOEXCEPTION);
+		}
+	}
+
+	/*
+	 * check second operand for NaN's or infinity
+	 */
+	if (Sgl_isinfinity_exponent(opnd2)) {
+		if (Sgl_iszero_mantissa(opnd2)) {
+			if (Sgl_isnotnan(opnd3)) {
+				if (Sgl_iszero_exponentmantissa(opnd1)) {
+					/* 
+					 * invalid since multiply operands are
+					 * zero & infinity
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Sgl_makequietnan(opnd2);
+					Sgl_copytoptr(opnd2,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+				 * Check third operand for infinity with a
+				 *  sign opposite of the multiply result
+				 */
+				if (Sgl_isinfinity(opnd3) &&
+				    (Sgl_sign(resultp1) ^ Sgl_sign(opnd3))) {
+					/* 
+					 * invalid since attempting a magnitude
+					 * subtraction of infinities
+					 */
+					if (Is_invalidtrap_enabled())
+				       		return(OPC_2E_INVALIDEXCEPTION);
+				       	Set_invalidflag();
+				       	Sgl_makequietnan(resultp1);
+					Sgl_copytoptr(resultp1,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+				 * return infinity
+				 */
+				Sgl_setinfinity_exponentmantissa(resultp1);
+				Sgl_copytoptr(resultp1,dstptr);
+				return(NOEXCEPTION);
+			}
+		}
+		else {
+			/*
+			 * is NaN; signaling or quiet?
+			 */
+			if (Sgl_isone_signaling(opnd2)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+					return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd2);
+			}
+			/* 
+			 * is third operand a signaling NaN? 
+			 */
+			else if (Sgl_is_signalingnan(opnd3)) {
+			       	/* trap if INVALIDTRAP enabled */
+			       	if (Is_invalidtrap_enabled())
+				   		return(OPC_2E_INVALIDEXCEPTION);
+			       	/* make NaN quiet */
+			       	Set_invalidflag();
+			       	Sgl_set_quiet(opnd3);
+				Sgl_copytoptr(opnd3,dstptr);
+		       		return(NOEXCEPTION);
+			}
+			/*
+			 * return quiet NaN
+			 */
+			Sgl_copytoptr(opnd2,dstptr);
+			return(NOEXCEPTION);
+		}
+	}
+
+	/*
+	 * check third operand for NaN's or infinity
+	 */
+	if (Sgl_isinfinity_exponent(opnd3)) {
+		if (Sgl_iszero_mantissa(opnd3)) {
+			/* return infinity */
+			Sgl_copytoptr(opnd3,dstptr);
+			return(NOEXCEPTION);
+		} else {
+			/*
+			 * is NaN; signaling or quiet?
+			 */
+			if (Sgl_isone_signaling(opnd3)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+					return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd3);
+			}
+			/*
+			 * return quiet NaN
+ 			 */
+			Sgl_copytoptr(opnd3,dstptr);
+			return(NOEXCEPTION);
+		}
+    	}
+
+	/*
+	 * Generate multiply mantissa
+	 */
+	if (Sgl_isnotzero_exponent(opnd1)) {
+		/* set hidden bit */
+		Sgl_clear_signexponent_set_hidden(opnd1);
+	}
+	else {
+		/* check for zero */
+		if (Sgl_iszero_mantissa(opnd1)) {
+			/*
+			 * Perform the add opnd3 with zero here.
+			 */
+			if (Sgl_iszero_exponentmantissa(opnd3)) {
+				if (Is_rounding_mode(ROUNDMINUS)) {
+					Sgl_or_signs(opnd3,resultp1);
+				} else {
+					Sgl_and_signs(opnd3,resultp1);
+				}
+			}
+			/*
+			 * Now let's check for trapped underflow case.
+			 */
+			else if (Sgl_iszero_exponent(opnd3) &&
+			         Is_underflowtrap_enabled()) {
+                    		/* need to normalize results mantissa */
+                    		sign_save = Sgl_signextendedsign(opnd3);
+				result_exponent = 0;
+                    		Sgl_leftshiftby1(opnd3);
+                    		Sgl_normalize(opnd3,result_exponent);
+                    		Sgl_set_sign(opnd3,/*using*/sign_save);
+                    		Sgl_setwrapped_exponent(opnd3,result_exponent,
+							unfl);
+                    		Sgl_copytoptr(opnd3,dstptr);
+                    		/* inexact = FALSE */
+                    		return(OPC_2E_UNDERFLOWEXCEPTION);
+			}
+			Sgl_copytoptr(opnd3,dstptr);
+			return(NOEXCEPTION);
+		}
+		/* is denormalized, adjust exponent */
+		Sgl_clear_signexponent(opnd1);
+		Sgl_leftshiftby1(opnd1);
+		Sgl_normalize(opnd1,mpy_exponent);
+	}
+	/* opnd2 needs to have hidden bit set with msb in hidden bit */
+	if (Sgl_isnotzero_exponent(opnd2)) {
+		Sgl_clear_signexponent_set_hidden(opnd2);
+	}
+	else {
+		/* check for zero */
+		if (Sgl_iszero_mantissa(opnd2)) {
+			/*
+			 * Perform the add opnd3 with zero here.
+			 */
+			if (Sgl_iszero_exponentmantissa(opnd3)) {
+				if (Is_rounding_mode(ROUNDMINUS)) {
+					Sgl_or_signs(opnd3,resultp1);
+				} else {
+					Sgl_and_signs(opnd3,resultp1);
+				}
+			}
+			/*
+			 * Now let's check for trapped underflow case.
+			 */
+			else if (Sgl_iszero_exponent(opnd3) &&
+			    Is_underflowtrap_enabled()) {
+                    		/* need to normalize results mantissa */
+                    		sign_save = Sgl_signextendedsign(opnd3);
+				result_exponent = 0;
+                    		Sgl_leftshiftby1(opnd3);
+                    		Sgl_normalize(opnd3,result_exponent);
+                    		Sgl_set_sign(opnd3,/*using*/sign_save);
+                    		Sgl_setwrapped_exponent(opnd3,result_exponent,
+							unfl);
+                    		Sgl_copytoptr(opnd3,dstptr);
+                    		/* inexact = FALSE */
+                    		return(OPC_2E_UNDERFLOWEXCEPTION);
+			}
+			Sgl_copytoptr(opnd3,dstptr);
+			return(NOEXCEPTION);
+		}
+		/* is denormalized; want to normalize */
+		Sgl_clear_signexponent(opnd2);
+		Sgl_leftshiftby1(opnd2);
+		Sgl_normalize(opnd2,mpy_exponent);
+	}
+
+	/* Multiply the first two source mantissas together */
+
+	/* 
+	 * The intermediate result will be kept in tmpres,
+	 * which needs enough room for 106 bits of mantissa,
+	 * so lets call it a Double extended.
+	 */
+	Sglext_setzero(tmpresp1,tmpresp2);
+
+	/* 
+	 * Four bits at a time are inspected in each loop, and a 
+	 * simple shift and add multiply algorithm is used. 
+	 */ 
+	for (count = SGL_P-1; count >= 0; count -= 4) {
+		Sglext_rightshiftby4(tmpresp1,tmpresp2);
+		if (Sbit28(opnd1)) {
+	 		/* Twoword_add should be an ADD followed by 2 ADDC's */
+			Twoword_add(tmpresp1, tmpresp2, opnd2<<3, 0);
+		}
+		if (Sbit29(opnd1)) {
+			Twoword_add(tmpresp1, tmpresp2, opnd2<<2, 0);
+		}
+		if (Sbit30(opnd1)) {
+			Twoword_add(tmpresp1, tmpresp2, opnd2<<1, 0);
+		}
+		if (Sbit31(opnd1)) {
+			Twoword_add(tmpresp1, tmpresp2, opnd2, 0);
+		}
+		Sgl_rightshiftby4(opnd1);
+	}
+	if (Is_sexthiddenoverflow(tmpresp1)) {
+		/* result mantissa >= 2 (mantissa overflow) */
+		mpy_exponent++;
+		Sglext_rightshiftby4(tmpresp1,tmpresp2);
+	} else {
+		Sglext_rightshiftby3(tmpresp1,tmpresp2);
+	}
+
+	/*
+	 * Restore the sign of the mpy result which was saved in resultp1.
+	 * The exponent will continue to be kept in mpy_exponent.
+	 */
+	Sglext_set_sign(tmpresp1,Sgl_sign(resultp1));
+
+	/* 
+	 * No rounding is required, since the result of the multiply
+	 * is exact in the extended format.
+	 */
+
+	/*
+	 * Now we are ready to perform the add portion of the operation.
+	 *
+	 * The exponents need to be kept as integers for now, since the
+	 * multiply result might not fit into the exponent field.  We
+	 * can't overflow or underflow because of this yet, since the
+	 * add could bring the final result back into range.
+	 */
+	add_exponent = Sgl_exponent(opnd3);
+
+	/*
+	 * Check for denormalized or zero add operand.
+	 */
+	if (add_exponent == 0) {
+		/* check for zero */
+		if (Sgl_iszero_mantissa(opnd3)) {
+			/* right is zero */
+			/* Left can't be zero and must be result.
+			 *
+			 * The final result is now in tmpres and mpy_exponent,
+			 * and needs to be rounded and squeezed back into
+			 * double precision format from double extended.
+			 */
+			result_exponent = mpy_exponent;
+			Sglext_copy(tmpresp1,tmpresp2,resultp1,resultp2);
+			sign_save = Sgl_signextendedsign(resultp1);/*save sign*/
+			goto round;
+		}
+
+		/* 
+		 * Neither are zeroes.  
+		 * Adjust exponent and normalize add operand.
+		 */
+		sign_save = Sgl_signextendedsign(opnd3);	/* save sign */
+		Sgl_clear_signexponent(opnd3);
+		Sgl_leftshiftby1(opnd3);
+		Sgl_normalize(opnd3,add_exponent);
+		Sgl_set_sign(opnd3,sign_save);		/* restore sign */
+	} else {
+		Sgl_clear_exponent_set_hidden(opnd3);
+	}
+	/*
+	 * Copy opnd3 to the double extended variable called right.
+	 */
+	Sgl_copyto_sglext(opnd3,rightp1,rightp2);
+
+	/*
+	 * A zero "save" helps discover equal operands (for later),
+	 * and is used in swapping operands (if needed).
+	 */
+	Sglext_xortointp1(tmpresp1,rightp1,/*to*/save);
+
+	/*
+	 * Compare magnitude of operands.
+	 */
+	Sglext_copytoint_exponentmantissa(tmpresp1,signlessleft1);
+	Sglext_copytoint_exponentmantissa(rightp1,signlessright1);
+	if (mpy_exponent < add_exponent || mpy_exponent == add_exponent &&
+	    Sglext_ismagnitudeless(signlessleft1,signlessright1)) {
+		/*
+		 * Set the left operand to the larger one by XOR swap.
+		 * First finish the first word "save".
+		 */
+		Sglext_xorfromintp1(save,rightp1,/*to*/rightp1);
+		Sglext_xorfromintp1(save,tmpresp1,/*to*/tmpresp1);
+		Sglext_swap_lower(tmpresp2,rightp2);
+		/* also setup exponents used in rest of routine */
+		diff_exponent = add_exponent - mpy_exponent;
+		result_exponent = add_exponent;
+	} else {
+		/* also setup exponents used in rest of routine */
+		diff_exponent = mpy_exponent - add_exponent;
+		result_exponent = mpy_exponent;
+	}
+	/* Invariant: left is not smaller than right. */
+
+	/*
+	 * 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 > SGLEXT_THRESHOLD) {
+		diff_exponent = SGLEXT_THRESHOLD;
+	}
+
+	/* Align right operand by shifting it to the right */
+	Sglext_clear_sign(rightp1);
+	Sglext_right_align(rightp1,rightp2,/*shifted by*/diff_exponent);
+	
+	/* Treat sum and difference of the operands separately. */
+	if ((int)save < 0) {
+		/*
+		 * Difference of the two operands.  Overflow can occur if the
+		 * multiply overflowed.  A borrow can occur out of the hidden
+		 * bit and force a post normalization phase.
+		 */
+		Sglext_subtract(tmpresp1,tmpresp2, rightp1,rightp2,
+			resultp1,resultp2);
+		sign_save = Sgl_signextendedsign(resultp1);
+		if (Sgl_iszero_hidden(resultp1)) {
+			/* 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. */
+			Sglext_leftshiftby1(resultp1,resultp2);
+
+			/* 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 (Sglext_iszero(resultp1,resultp2)) {
+				/* Must have been "x-x" or "x+(-x)". */
+				if (Is_rounding_mode(ROUNDMINUS))
+					Sgl_setone_sign(resultp1);
+				Sgl_copytoptr(resultp1,dstptr);
+				return(NOEXCEPTION);
+			}
+			result_exponent--;
+
+			/* Look to see if normalization is finished. */
+			if (Sgl_isone_hidden(resultp1)) {
+				/* No further normalization is needed */
+				goto round;
+			}
+
+			/* 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(resultp1)) {
+				Sglext_leftshiftby8(resultp1,resultp2);
+				result_exponent -= 8;
+			}
+			/* Now narrow it down to the nibble */
+			if (Sgl_iszero_hiddenhigh3mantissa(resultp1)) {
+				/* The lower nibble contains the
+				 * normalizing one */
+				Sglext_leftshiftby4(resultp1,resultp2);
+				result_exponent -= 4;
+			}
+			/* Select case where first bit is set (already
+			 * normalized) otherwise select the proper shift. */
+			jumpsize = Sgl_hiddenhigh3mantissa(resultp1);
+			if (jumpsize <= 7) switch(jumpsize) {
+			case 1:
+				Sglext_leftshiftby3(resultp1,resultp2);
+				result_exponent -= 3;
+				break;
+			case 2:
+			case 3:
+				Sglext_leftshiftby2(resultp1,resultp2);
+				result_exponent -= 2;
+				break;
+			case 4:
+			case 5:
+			case 6:
+			case 7:
+				Sglext_leftshiftby1(resultp1,resultp2);
+				result_exponent -= 1;
+				break;
+			}
+		} /* end if (hidden...)... */
+	/* Fall through and round */
+	} /* end if (save < 0)... */
+	else {
+		/* Add magnitudes */
+		Sglext_addition(tmpresp1,tmpresp2,
+			rightp1,rightp2, /*to*/resultp1,resultp2);
+		sign_save = Sgl_signextendedsign(resultp1);
+		if (Sgl_isone_hiddenoverflow(resultp1)) {
+	    		/* Prenormalization required. */
+	    		Sglext_arithrightshiftby1(resultp1,resultp2);
+	    		result_exponent++;
+		} /* end if hiddenoverflow... */
+	} /* end else ...add magnitudes... */
+
+	/* Round the result.  If the extension and lower two words are
+	 * all zeros, then the result is exact.  Otherwise round in the
+	 * correct direction.  Underflow is possible. If a postnormalization
+	 * is necessary, then the mantissa is all zeros so no shift is needed.
+	 */
+  round:
+	if (result_exponent <= 0 && !Is_underflowtrap_enabled()) {
+		Sglext_denormalize(resultp1,resultp2,result_exponent,is_tiny);
+	}
+	Sgl_set_sign(resultp1,/*using*/sign_save);
+	if (Sglext_isnotzero_mantissap2(resultp2)) {
+		inexact = TRUE;
+		switch(Rounding_mode()) {
+		case ROUNDNEAREST: /* The default. */
+			if (Sglext_isone_highp2(resultp2)) {
+				/* at least 1/2 ulp */
+				if (Sglext_isnotzero_low31p2(resultp2) ||
+				    Sglext_isone_lowp1(resultp1)) {
+					/* either exactly half way and odd or
+					 * more than 1/2ulp */
+					Sgl_increment(resultp1);
+				}
+			}
+	    		break;
+
+		case ROUNDPLUS:
+	    		if (Sgl_iszero_sign(resultp1)) {
+				/* Round up positive results */
+				Sgl_increment(resultp1);
+			}
+			break;
+	    
+		case ROUNDMINUS:
+	    		if (Sgl_isone_sign(resultp1)) {
+				/* Round down negative results */
+				Sgl_increment(resultp1);
+			}
+	    
+		case ROUNDZERO:;
+			/* truncate is simple */
+		} /* end switch... */
+		if (Sgl_isone_hiddenoverflow(resultp1)) result_exponent++;
+	}
+	if (result_exponent >= SGL_INFINITY_EXPONENT) {
+		/* Overflow */
+		if (Is_overflowtrap_enabled()) {
+                        /*
+                         * Adjust bias of result
+                         */
+                        Sgl_setwrapped_exponent(resultp1,result_exponent,ovfl);
+                        Sgl_copytoptr(resultp1,dstptr);
+                        if (inexact)
+                            if (Is_inexacttrap_enabled())
+                                return (OPC_2E_OVERFLOWEXCEPTION |
+					OPC_2E_INEXACTEXCEPTION);
+                            else Set_inexactflag();
+                        return (OPC_2E_OVERFLOWEXCEPTION);
+		}
+		inexact = TRUE;
+		Set_overflowflag();
+		Sgl_setoverflow(resultp1);
+	} else if (result_exponent <= 0) {	/* underflow case */
+		if (Is_underflowtrap_enabled()) {
+                        /*
+                         * Adjust bias of result
+                         */
+                	Sgl_setwrapped_exponent(resultp1,result_exponent,unfl);
+			Sgl_copytoptr(resultp1,dstptr);
+                        if (inexact)
+                            if (Is_inexacttrap_enabled())
+                                return (OPC_2E_UNDERFLOWEXCEPTION |
+					OPC_2E_INEXACTEXCEPTION);
+                            else Set_inexactflag();
+	    		return(OPC_2E_UNDERFLOWEXCEPTION);
+		}
+		else if (inexact && is_tiny) Set_underflowflag();
+	}
+	else Sgl_set_exponent(resultp1,result_exponent);
+	Sgl_copytoptr(resultp1,dstptr);
+	if (inexact) 
+		if (Is_inexacttrap_enabled()) return(OPC_2E_INEXACTEXCEPTION);
+		else Set_inexactflag();
+    	return(NOEXCEPTION);
+}
+
+/*
+ *  Single Floating-point Multiply Negate Fused Add
+ */
+
+sgl_fmpynfadd(src1ptr,src2ptr,src3ptr,status,dstptr)
+
+sgl_floating_point *src1ptr, *src2ptr, *src3ptr, *dstptr;
+unsigned int *status;
+{
+	unsigned int opnd1, opnd2, opnd3;
+	register unsigned int tmpresp1, tmpresp2;
+	unsigned int rightp1, rightp2;
+	unsigned int resultp1, resultp2 = 0;
+	register int mpy_exponent, add_exponent, count;
+	boolean inexact = FALSE, is_tiny = FALSE;
+
+	unsigned int signlessleft1, signlessright1, save;
+	register int result_exponent, diff_exponent;
+	int sign_save, jumpsize;
+	
+	Sgl_copyfromptr(src1ptr,opnd1);
+	Sgl_copyfromptr(src2ptr,opnd2);
+	Sgl_copyfromptr(src3ptr,opnd3);
+
+	/* 
+	 * set sign bit of result of multiply
+	 */
+	if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) 
+		Sgl_setzero(resultp1);
+	else 
+		Sgl_setnegativezero(resultp1); 
+
+	/*
+	 * Generate multiply exponent 
+	 */
+	mpy_exponent = Sgl_exponent(opnd1) + Sgl_exponent(opnd2) - SGL_BIAS;
+
+	/*
+	 * check first operand for NaN's or infinity
+	 */
+	if (Sgl_isinfinity_exponent(opnd1)) {
+		if (Sgl_iszero_mantissa(opnd1)) {
+			if (Sgl_isnotnan(opnd2) && Sgl_isnotnan(opnd3)) {
+				if (Sgl_iszero_exponentmantissa(opnd2)) {
+					/* 
+					 * invalid since operands are infinity 
+					 * and zero 
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Sgl_makequietnan(resultp1);
+					Sgl_copytoptr(resultp1,dstptr);
+					return(NOEXCEPTION);
+				}
+				/*
+				 * Check third operand for infinity with a
+				 *  sign opposite of the multiply result
+				 */
+				if (Sgl_isinfinity(opnd3) &&
+				    (Sgl_sign(resultp1) ^ Sgl_sign(opnd3))) {
+					/* 
+					 * invalid since attempting a magnitude
+					 * subtraction of infinities
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Sgl_makequietnan(resultp1);
+					Sgl_copytoptr(resultp1,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+			 	 * return infinity
+			 	 */
+				Sgl_setinfinity_exponentmantissa(resultp1);
+				Sgl_copytoptr(resultp1,dstptr);
+				return(NOEXCEPTION);
+			}
+		}
+		else {
+			/*
+		 	 * is NaN; signaling or quiet?
+		 	 */
+			if (Sgl_isone_signaling(opnd1)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled()) 
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd1);
+			}
+			/* 
+			 * is second operand a signaling NaN? 
+			 */
+			else if (Sgl_is_signalingnan(opnd2)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd2);
+				Sgl_copytoptr(opnd2,dstptr);
+				return(NOEXCEPTION);
+			}
+			/* 
+			 * is third operand a signaling NaN? 
+			 */
+			else if (Sgl_is_signalingnan(opnd3)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+			    		return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd3);
+				Sgl_copytoptr(opnd3,dstptr);
+				return(NOEXCEPTION);
+			}
+			/*
+		 	 * return quiet NaN
+		 	 */
+			Sgl_copytoptr(opnd1,dstptr);
+			return(NOEXCEPTION);
+		}
+	}
+
+	/*
+	 * check second operand for NaN's or infinity
+	 */
+	if (Sgl_isinfinity_exponent(opnd2)) {
+		if (Sgl_iszero_mantissa(opnd2)) {
+			if (Sgl_isnotnan(opnd3)) {
+				if (Sgl_iszero_exponentmantissa(opnd1)) {
+					/* 
+					 * invalid since multiply operands are
+					 * zero & infinity
+					 */
+					if (Is_invalidtrap_enabled())
+						return(OPC_2E_INVALIDEXCEPTION);
+					Set_invalidflag();
+					Sgl_makequietnan(opnd2);
+					Sgl_copytoptr(opnd2,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+				 * Check third operand for infinity with a
+				 *  sign opposite of the multiply result
+				 */
+				if (Sgl_isinfinity(opnd3) &&
+				    (Sgl_sign(resultp1) ^ Sgl_sign(opnd3))) {
+					/* 
+					 * invalid since attempting a magnitude
+					 * subtraction of infinities
+					 */
+					if (Is_invalidtrap_enabled())
+				       		return(OPC_2E_INVALIDEXCEPTION);
+				       	Set_invalidflag();
+				       	Sgl_makequietnan(resultp1);
+					Sgl_copytoptr(resultp1,dstptr);
+					return(NOEXCEPTION);
+				}
+
+				/*
+				 * return infinity
+				 */
+				Sgl_setinfinity_exponentmantissa(resultp1);
+				Sgl_copytoptr(resultp1,dstptr);
+				return(NOEXCEPTION);
+			}
+		}
+		else {
+			/*
+			 * is NaN; signaling or quiet?
+			 */
+			if (Sgl_isone_signaling(opnd2)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+					return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd2);
+			}
+			/* 
+			 * is third operand a signaling NaN? 
+			 */
+			else if (Sgl_is_signalingnan(opnd3)) {
+			       	/* trap if INVALIDTRAP enabled */
+			       	if (Is_invalidtrap_enabled())
+				   		return(OPC_2E_INVALIDEXCEPTION);
+			       	/* make NaN quiet */
+			       	Set_invalidflag();
+			       	Sgl_set_quiet(opnd3);
+				Sgl_copytoptr(opnd3,dstptr);
+		       		return(NOEXCEPTION);
+			}
+			/*
+			 * return quiet NaN
+			 */
+			Sgl_copytoptr(opnd2,dstptr);
+			return(NOEXCEPTION);
+		}
+	}
+
+	/*
+	 * check third operand for NaN's or infinity
+	 */
+	if (Sgl_isinfinity_exponent(opnd3)) {
+		if (Sgl_iszero_mantissa(opnd3)) {
+			/* return infinity */
+			Sgl_copytoptr(opnd3,dstptr);
+			return(NOEXCEPTION);
+		} else {
+			/*
+			 * is NaN; signaling or quiet?
+			 */
+			if (Sgl_isone_signaling(opnd3)) {
+				/* trap if INVALIDTRAP enabled */
+				if (Is_invalidtrap_enabled())
+					return(OPC_2E_INVALIDEXCEPTION);
+				/* make NaN quiet */
+				Set_invalidflag();
+				Sgl_set_quiet(opnd3);
+			}
+			/*
+			 * return quiet NaN
+ 			 */
+			Sgl_copytoptr(opnd3,dstptr);
+			return(NOEXCEPTION);
+		}
+    	}
+
+	/*
+	 * Generate multiply mantissa
+	 */
+	if (Sgl_isnotzero_exponent(opnd1)) {
+		/* set hidden bit */
+		Sgl_clear_signexponent_set_hidden(opnd1);
+	}
+	else {
+		/* check for zero */
+		if (Sgl_iszero_mantissa(opnd1)) {
+			/*
+			 * Perform the add opnd3 with zero here.
+			 */
+			if (Sgl_iszero_exponentmantissa(opnd3)) {
+				if (Is_rounding_mode(ROUNDMINUS)) {
+					Sgl_or_signs(opnd3,resultp1);
+				} else {
+					Sgl_and_signs(opnd3,resultp1);
+				}
+			}
+			/*
+			 * Now let's check for trapped underflow case.
+			 */
+			else if (Sgl_iszero_exponent(opnd3) &&
+			         Is_underflowtrap_enabled()) {
+                    		/* need to normalize results mantissa */
+                    		sign_save = Sgl_signextendedsign(opnd3);
+				result_exponent = 0;
+                    		Sgl_leftshiftby1(opnd3);
+                    		Sgl_normalize(opnd3,result_exponent);
+                    		Sgl_set_sign(opnd3,/*using*/sign_save);
+                    		Sgl_setwrapped_exponent(opnd3,result_exponent,
+							unfl);
+                    		Sgl_copytoptr(opnd3,dstptr);
+                    		/* inexact = FALSE */
+                    		return(OPC_2E_UNDERFLOWEXCEPTION);
+			}
+			Sgl_copytoptr(opnd3,dstptr);
+			return(NOEXCEPTION);
+		}
+		/* is denormalized, adjust exponent */
+		Sgl_clear_signexponent(opnd1);
+		Sgl_leftshiftby1(opnd1);
+		Sgl_normalize(opnd1,mpy_exponent);
+	}
+	/* opnd2 needs to have hidden bit set with msb in hidden bit */
+	if (Sgl_isnotzero_exponent(opnd2)) {
+		Sgl_clear_signexponent_set_hidden(opnd2);
+	}
+	else {
+		/* check for zero */
+		if (Sgl_iszero_mantissa(opnd2)) {
+			/*
+			 * Perform the add opnd3 with zero here.
+			 */
+			if (Sgl_iszero_exponentmantissa(opnd3)) {
+				if (Is_rounding_mode(ROUNDMINUS)) {
+					Sgl_or_signs(opnd3,resultp1);
+				} else {
+					Sgl_and_signs(opnd3,resultp1);
+				}
+			}
+			/*
+			 * Now let's check for trapped underflow case.
+			 */
+			else if (Sgl_iszero_exponent(opnd3) &&
+			    Is_underflowtrap_enabled()) {
+                    		/* need to normalize results mantissa */
+                    		sign_save = Sgl_signextendedsign(opnd3);
+				result_exponent = 0;
+                    		Sgl_leftshiftby1(opnd3);
+                    		Sgl_normalize(opnd3,result_exponent);
+                    		Sgl_set_sign(opnd3,/*using*/sign_save);
+                    		Sgl_setwrapped_exponent(opnd3,result_exponent,
+							unfl);
+                    		Sgl_copytoptr(opnd3,dstptr);
+                    		/* inexact = FALSE */
+                    		return(OPC_2E_UNDERFLOWEXCEPTION);
+			}
+			Sgl_copytoptr(opnd3,dstptr);
+			return(NOEXCEPTION);
+		}
+		/* is denormalized; want to normalize */
+		Sgl_clear_signexponent(opnd2);
+		Sgl_leftshiftby1(opnd2);
+		Sgl_normalize(opnd2,mpy_exponent);
+	}
+
+	/* Multiply the first two source mantissas together */
+
+	/* 
+	 * The intermediate result will be kept in tmpres,
+	 * which needs enough room for 106 bits of mantissa,
+	 * so lets call it a Double extended.
+	 */
+	Sglext_setzero(tmpresp1,tmpresp2);
+
+	/* 
+	 * Four bits at a time are inspected in each loop, and a 
+	 * simple shift and add multiply algorithm is used. 
+	 */ 
+	for (count = SGL_P-1; count >= 0; count -= 4) {
+		Sglext_rightshiftby4(tmpresp1,tmpresp2);
+		if (Sbit28(opnd1)) {
+	 		/* Twoword_add should be an ADD followed by 2 ADDC's */
+			Twoword_add(tmpresp1, tmpresp2, opnd2<<3, 0);
+		}
+		if (Sbit29(opnd1)) {
+			Twoword_add(tmpresp1, tmpresp2, opnd2<<2, 0);
+		}
+		if (Sbit30(opnd1)) {
+			Twoword_add(tmpresp1, tmpresp2, opnd2<<1, 0);
+		}
+		if (Sbit31(opnd1)) {
+			Twoword_add(tmpresp1, tmpresp2, opnd2, 0);
+		}
+		Sgl_rightshiftby4(opnd1);
+	}
+	if (Is_sexthiddenoverflow(tmpresp1)) {
+		/* result mantissa >= 2 (mantissa overflow) */
+		mpy_exponent++;
+		Sglext_rightshiftby4(tmpresp1,tmpresp2);
+	} else {
+		Sglext_rightshiftby3(tmpresp1,tmpresp2);
+	}
+
+	/*
+	 * Restore the sign of the mpy result which was saved in resultp1.
+	 * The exponent will continue to be kept in mpy_exponent.
+	 */
+	Sglext_set_sign(tmpresp1,Sgl_sign(resultp1));
+
+	/* 
+	 * No rounding is required, since the result of the multiply
+	 * is exact in the extended format.
+	 */
+
+	/*
+	 * Now we are ready to perform the add portion of the operation.
+	 *
+	 * The exponents need to be kept as integers for now, since the
+	 * multiply result might not fit into the exponent field.  We
+	 * can't overflow or underflow because of this yet, since the
+	 * add could bring the final result back into range.
+	 */
+	add_exponent = Sgl_exponent(opnd3);
+
+	/*
+	 * Check for denormalized or zero add operand.
+	 */
+	if (add_exponent == 0) {
+		/* check for zero */
+		if (Sgl_iszero_mantissa(opnd3)) {
+			/* right is zero */
+			/* Left can't be zero and must be result.
+			 *
+			 * The final result is now in tmpres and mpy_exponent,
+			 * and needs to be rounded and squeezed back into
+			 * double precision format from double extended.
+			 */
+			result_exponent = mpy_exponent;
+			Sglext_copy(tmpresp1,tmpresp2,resultp1,resultp2);
+			sign_save = Sgl_signextendedsign(resultp1);/*save sign*/
+			goto round;
+		}
+
+		/* 
+		 * Neither are zeroes.  
+		 * Adjust exponent and normalize add operand.
+		 */
+		sign_save = Sgl_signextendedsign(opnd3);	/* save sign */
+		Sgl_clear_signexponent(opnd3);
+		Sgl_leftshiftby1(opnd3);
+		Sgl_normalize(opnd3,add_exponent);
+		Sgl_set_sign(opnd3,sign_save);		/* restore sign */
+	} else {
+		Sgl_clear_exponent_set_hidden(opnd3);
+	}
+	/*
+	 * Copy opnd3 to the double extended variable called right.
+	 */
+	Sgl_copyto_sglext(opnd3,rightp1,rightp2);
+
+	/*
+	 * A zero "save" helps discover equal operands (for later),
+	 * and is used in swapping operands (if needed).
+	 */
+	Sglext_xortointp1(tmpresp1,rightp1,/*to*/save);
+
+	/*
+	 * Compare magnitude of operands.
+	 */
+	Sglext_copytoint_exponentmantissa(tmpresp1,signlessleft1);
+	Sglext_copytoint_exponentmantissa(rightp1,signlessright1);
+	if (mpy_exponent < add_exponent || mpy_exponent == add_exponent &&
+	    Sglext_ismagnitudeless(signlessleft1,signlessright1)) {
+		/*
+		 * Set the left operand to the larger one by XOR swap.
+		 * First finish the first word "save".
+		 */
+		Sglext_xorfromintp1(save,rightp1,/*to*/rightp1);
+		Sglext_xorfromintp1(save,tmpresp1,/*to*/tmpresp1);
+		Sglext_swap_lower(tmpresp2,rightp2);
+		/* also setup exponents used in rest of routine */
+		diff_exponent = add_exponent - mpy_exponent;
+		result_exponent = add_exponent;
+	} else {
+		/* also setup exponents used in rest of routine */
+		diff_exponent = mpy_exponent - add_exponent;
+		result_exponent = mpy_exponent;
+	}
+	/* Invariant: left is not smaller than right. */
+
+	/*
+	 * 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 > SGLEXT_THRESHOLD) {
+		diff_exponent = SGLEXT_THRESHOLD;
+	}
+
+	/* Align right operand by shifting it to the right */
+	Sglext_clear_sign(rightp1);
+	Sglext_right_align(rightp1,rightp2,/*shifted by*/diff_exponent);
+	
+	/* Treat sum and difference of the operands separately. */
+	if ((int)save < 0) {
+		/*
+		 * Difference of the two operands.  Overflow can occur if the
+		 * multiply overflowed.  A borrow can occur out of the hidden
+		 * bit and force a post normalization phase.
+		 */
+		Sglext_subtract(tmpresp1,tmpresp2, rightp1,rightp2,
+			resultp1,resultp2);
+		sign_save = Sgl_signextendedsign(resultp1);
+		if (Sgl_iszero_hidden(resultp1)) {
+			/* 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. */
+			Sglext_leftshiftby1(resultp1,resultp2);
+
+			/* 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 (Sglext_iszero(resultp1,resultp2)) {
+				/* Must have been "x-x" or "x+(-x)". */
+				if (Is_rounding_mode(ROUNDMINUS))
+					Sgl_setone_sign(resultp1);
+				Sgl_copytoptr(resultp1,dstptr);
+				return(NOEXCEPTION);
+			}
+			result_exponent--;
+
+			/* Look to see if normalization is finished. */
+			if (Sgl_isone_hidden(resultp1)) {
+				/* No further normalization is needed */
+				goto round;
+			}
+
+			/* 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(resultp1)) {
+				Sglext_leftshiftby8(resultp1,resultp2);
+				result_exponent -= 8;
+			}
+			/* Now narrow it down to the nibble */
+			if (Sgl_iszero_hiddenhigh3mantissa(resultp1)) {
+				/* The lower nibble contains the
+				 * normalizing one */
+				Sglext_leftshiftby4(resultp1,resultp2);
+				result_exponent -= 4;
+			}
+			/* Select case where first bit is set (already
+			 * normalized) otherwise select the proper shift. */
+			jumpsize = Sgl_hiddenhigh3mantissa(resultp1);
+			if (jumpsize <= 7) switch(jumpsize) {
+			case 1:
+				Sglext_leftshiftby3(resultp1,resultp2);
+				result_exponent -= 3;
+				break;
+			case 2:
+			case 3:
+				Sglext_leftshiftby2(resultp1,resultp2);
+				result_exponent -= 2;
+				break;
+			case 4:
+			case 5:
+			case 6:
+			case 7:
+				Sglext_leftshiftby1(resultp1,resultp2);
+				result_exponent -= 1;
+				break;
+			}
+		} /* end if (hidden...)... */
+	/* Fall through and round */
+	} /* end if (save < 0)... */
+	else {
+		/* Add magnitudes */
+		Sglext_addition(tmpresp1,tmpresp2,
+			rightp1,rightp2, /*to*/resultp1,resultp2);
+		sign_save = Sgl_signextendedsign(resultp1);
+		if (Sgl_isone_hiddenoverflow(resultp1)) {
+	    		/* Prenormalization required. */
+	    		Sglext_arithrightshiftby1(resultp1,resultp2);
+	    		result_exponent++;
+		} /* end if hiddenoverflow... */
+	} /* end else ...add magnitudes... */
+
+	/* Round the result.  If the extension and lower two words are
+	 * all zeros, then the result is exact.  Otherwise round in the
+	 * correct direction.  Underflow is possible. If a postnormalization
+	 * is necessary, then the mantissa is all zeros so no shift is needed.
+	 */
+  round:
+	if (result_exponent <= 0 && !Is_underflowtrap_enabled()) {
+		Sglext_denormalize(resultp1,resultp2,result_exponent,is_tiny);
+	}
+	Sgl_set_sign(resultp1,/*using*/sign_save);
+	if (Sglext_isnotzero_mantissap2(resultp2)) {
+		inexact = TRUE;
+		switch(Rounding_mode()) {
+		case ROUNDNEAREST: /* The default. */
+			if (Sglext_isone_highp2(resultp2)) {
+				/* at least 1/2 ulp */
+				if (Sglext_isnotzero_low31p2(resultp2) ||
+				    Sglext_isone_lowp1(resultp1)) {
+					/* either exactly half way and odd or
+					 * more than 1/2ulp */
+					Sgl_increment(resultp1);
+				}
+			}
+	    		break;
+
+		case ROUNDPLUS:
+	    		if (Sgl_iszero_sign(resultp1)) {
+				/* Round up positive results */
+				Sgl_increment(resultp1);
+			}
+			break;
+	    
+		case ROUNDMINUS:
+	    		if (Sgl_isone_sign(resultp1)) {
+				/* Round down negative results */
+				Sgl_increment(resultp1);
+			}
+	    
+		case ROUNDZERO:;
+			/* truncate is simple */
+		} /* end switch... */
+		if (Sgl_isone_hiddenoverflow(resultp1)) result_exponent++;
+	}
+	if (result_exponent >= SGL_INFINITY_EXPONENT) {
+		/* Overflow */
+		if (Is_overflowtrap_enabled()) {
+                        /*
+                         * Adjust bias of result
+                         */
+                        Sgl_setwrapped_exponent(resultp1,result_exponent,ovfl);
+                        Sgl_copytoptr(resultp1,dstptr);
+                        if (inexact)
+                            if (Is_inexacttrap_enabled())
+                                return (OPC_2E_OVERFLOWEXCEPTION |
+					OPC_2E_INEXACTEXCEPTION);
+                            else Set_inexactflag();
+                        return (OPC_2E_OVERFLOWEXCEPTION);
+		}
+		inexact = TRUE;
+		Set_overflowflag();
+		Sgl_setoverflow(resultp1);
+	} else if (result_exponent <= 0) {	/* underflow case */
+		if (Is_underflowtrap_enabled()) {
+                        /*
+                         * Adjust bias of result
+                         */
+                	Sgl_setwrapped_exponent(resultp1,result_exponent,unfl);
+			Sgl_copytoptr(resultp1,dstptr);
+                        if (inexact)
+                            if (Is_inexacttrap_enabled())
+                                return (OPC_2E_UNDERFLOWEXCEPTION |
+					OPC_2E_INEXACTEXCEPTION);
+                            else Set_inexactflag();
+	    		return(OPC_2E_UNDERFLOWEXCEPTION);
+		}
+		else if (inexact && is_tiny) Set_underflowflag();
+	}
+	else Sgl_set_exponent(resultp1,result_exponent);
+	Sgl_copytoptr(resultp1,dstptr);
+	if (inexact) 
+		if (Is_inexacttrap_enabled()) return(OPC_2E_INEXACTEXCEPTION);
+		else Set_inexactflag();
+    	return(NOEXCEPTION);
+}
+