From ace9429bb58fd418f0c81d4c2835699bddf6bde6 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Thu, 11 Apr 2024 10:27:49 +0200
Subject: Adding upstream version 6.6.15.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 arch/parisc/math-emu/dfsqrt.c | 182 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 182 insertions(+)
 create mode 100644 arch/parisc/math-emu/dfsqrt.c

(limited to 'arch/parisc/math-emu/dfsqrt.c')

diff --git a/arch/parisc/math-emu/dfsqrt.c b/arch/parisc/math-emu/dfsqrt.c
new file mode 100644
index 0000000000..63d339c81c
--- /dev/null
+++ b/arch/parisc/math-emu/dfsqrt.c
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Linux/PA-RISC Project (http://www.parisc-linux.org/)
+ *
+ * Floating-point emulation code
+ *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
+ */
+/*
+ * BEGIN_DESC
+ *
+ *  File:
+ *	@(#)	pa/spmath/dfsqrt.c		$Revision: 1.1 $
+ *
+ *  Purpose:
+ *	Double Floating-point Square Root
+ *
+ *  External Interfaces:
+ *	dbl_fsqrt(srcptr,nullptr,dstptr,status)
+ *
+ *  Internal Interfaces:
+ *
+ *  Theory:
+ *	<<please update with a overview of the operation of this file>>
+ *
+ * END_DESC
+*/
+
+
+#include "float.h"
+#include "dbl_float.h"
+
+/*
+ *  Double Floating-point Square Root
+ */
+
+/*ARGSUSED*/
+unsigned int
+dbl_fsqrt(
+	    dbl_floating_point *srcptr,
+	    unsigned int *nullptr,
+	    dbl_floating_point *dstptr,
+	    unsigned int *status)
+{
+	register unsigned int srcp1, srcp2, resultp1, resultp2;
+	register unsigned int newbitp1, newbitp2, sump1, sump2;
+	register int src_exponent;
+	register boolean guardbit = FALSE, even_exponent;
+
+	Dbl_copyfromptr(srcptr,srcp1,srcp2);
+        /*
+         * check source operand for NaN or infinity
+         */
+        if ((src_exponent = Dbl_exponent(srcp1)) == DBL_INFINITY_EXPONENT) {
+                /*
+                 * is signaling NaN?
+                 */
+                if (Dbl_isone_signaling(srcp1)) {
+                        /* trap if INVALIDTRAP enabled */
+                        if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
+                        /* make NaN quiet */
+                        Set_invalidflag();
+                        Dbl_set_quiet(srcp1);
+                }
+                /*
+                 * Return quiet NaN or positive infinity.
+		 *  Fall through to negative test if negative infinity.
+                 */
+		if (Dbl_iszero_sign(srcp1) || 
+		    Dbl_isnotzero_mantissa(srcp1,srcp2)) {
+                	Dbl_copytoptr(srcp1,srcp2,dstptr);
+                	return(NOEXCEPTION);
+		}
+        }
+
+        /*
+         * check for zero source operand
+         */
+	if (Dbl_iszero_exponentmantissa(srcp1,srcp2)) {
+		Dbl_copytoptr(srcp1,srcp2,dstptr);
+		return(NOEXCEPTION);
+	}
+
+        /*
+         * check for negative source operand 
+         */
+	if (Dbl_isone_sign(srcp1)) {
+		/* trap if INVALIDTRAP enabled */
+		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
+		/* make NaN quiet */
+		Set_invalidflag();
+		Dbl_makequietnan(srcp1,srcp2);
+		Dbl_copytoptr(srcp1,srcp2,dstptr);
+		return(NOEXCEPTION);
+	}
+
+	/*
+	 * Generate result
+	 */
+	if (src_exponent > 0) {
+		even_exponent = Dbl_hidden(srcp1);
+		Dbl_clear_signexponent_set_hidden(srcp1);
+	}
+	else {
+		/* normalize operand */
+		Dbl_clear_signexponent(srcp1);
+		src_exponent++;
+		Dbl_normalize(srcp1,srcp2,src_exponent);
+		even_exponent = src_exponent & 1;
+	}
+	if (even_exponent) {
+		/* exponent is even */
+		/* Add comment here.  Explain why odd exponent needs correction */
+		Dbl_leftshiftby1(srcp1,srcp2);
+	}
+	/*
+	 * Add comment here.  Explain following algorithm.
+	 * 
+	 * Trust me, it works.
+	 *
+	 */
+	Dbl_setzero(resultp1,resultp2);
+	Dbl_allp1(newbitp1) = 1 << (DBL_P - 32);
+	Dbl_setzero_mantissap2(newbitp2);
+	while (Dbl_isnotzero(newbitp1,newbitp2) && Dbl_isnotzero(srcp1,srcp2)) {
+		Dbl_addition(resultp1,resultp2,newbitp1,newbitp2,sump1,sump2);
+		if(Dbl_isnotgreaterthan(sump1,sump2,srcp1,srcp2)) {
+			Dbl_leftshiftby1(newbitp1,newbitp2);
+			/* update result */
+			Dbl_addition(resultp1,resultp2,newbitp1,newbitp2,
+			 resultp1,resultp2);  
+			Dbl_subtract(srcp1,srcp2,sump1,sump2,srcp1,srcp2);
+			Dbl_rightshiftby2(newbitp1,newbitp2);
+		}
+		else {
+			Dbl_rightshiftby1(newbitp1,newbitp2);
+		}
+		Dbl_leftshiftby1(srcp1,srcp2);
+	}
+	/* correct exponent for pre-shift */
+	if (even_exponent) {
+		Dbl_rightshiftby1(resultp1,resultp2);
+	}
+
+	/* check for inexact */
+	if (Dbl_isnotzero(srcp1,srcp2)) {
+		if (!even_exponent && Dbl_islessthan(resultp1,resultp2,srcp1,srcp2)) {
+			Dbl_increment(resultp1,resultp2);
+		}
+		guardbit = Dbl_lowmantissap2(resultp2);
+		Dbl_rightshiftby1(resultp1,resultp2);
+
+		/*  now round result  */
+		switch (Rounding_mode()) {
+		case ROUNDPLUS:
+		     Dbl_increment(resultp1,resultp2);
+		     break;
+		case ROUNDNEAREST:
+		     /* stickybit is always true, so guardbit 
+		      * is enough to determine rounding */
+		     if (guardbit) {
+			    Dbl_increment(resultp1,resultp2);
+		     }
+		     break;
+		}
+		/* increment result exponent by 1 if mantissa overflowed */
+		if (Dbl_isone_hiddenoverflow(resultp1)) src_exponent+=2;
+
+		if (Is_inexacttrap_enabled()) {
+			Dbl_set_exponent(resultp1,
+			 ((src_exponent-DBL_BIAS)>>1)+DBL_BIAS);
+			Dbl_copytoptr(resultp1,resultp2,dstptr);
+			return(INEXACTEXCEPTION);
+		}
+		else Set_inexactflag();
+	}
+	else {
+		Dbl_rightshiftby1(resultp1,resultp2);
+	}
+	Dbl_set_exponent(resultp1,((src_exponent-DBL_BIAS)>>1)+DBL_BIAS);
+	Dbl_copytoptr(resultp1,resultp2,dstptr);
+	return(NOEXCEPTION);
+}
-- 
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