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      1 /*	$NetBSD: fpsetsticky.c,v 1.1 2014/09/03 19:34:25 matt Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1999 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Dan Winship.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 __RCSID("$NetBSD: fpsetsticky.c,v 1.1 2014/09/03 19:34:25 matt Exp $");
     35 #endif /* LIBC_SCCS and not lint */
     36 
     37 #include "namespace.h"
     38 
     39 #include <sys/types.h>
     40 #include <ieeefp.h>
     41 #include <powerpc/fpu.h>
     42 
     43 #define	STICKYBITS	(FPSCR_XX|FPSCR_ZX|FPSCR_UX|FPSCR_OX|FPSCR_VX)
     44 #define	INVBITS		(FPSCR_VXCVI|FPSCR_VXSQRT|FPSCR_VXSOFT|FPSCR_VXVC|\
     45 			 FPSCR_VXIMZ|FPSCR_VXZDZ|FPSCR_VXIDI|FPSCR_VXISI|\
     46 			 FPSCR_VXSNAN)
     47 #define	STICKYSHFT	25
     48 
     49 #ifdef __weak_alias
     50 __weak_alias(fpsetsticky,_fpsetsticky)
     51 #endif
     52 
     53 fp_except
     54 fpsetsticky(fp_except mask)
     55 {
     56 	union {
     57 		double u_d;
     58 		uint64_t u_fpscr;
     59 	} ud;
     60 	fp_except old;
     61 
     62 	__asm volatile("mffs %0" : "=f"(ud.u_d));
     63 	old = ((uint32_t)ud.u_fpscr & STICKYBITS) >> STICKYSHFT;
     64 	/*
     65 	 * FPSCR_VX (aka FP_X_INV) is not a sticky bit but a summary of the
     66 	 * all the FPSCR_VX* sticky bits.  So when FP_X_INV is cleared then
     67 	 * clear all of those bits, likewise when it's set, set them all.
     68 	 */
     69 	if ((mask & FP_X_INV) == 0)
     70 		ud.u_fpscr &= ~INVBITS;
     71 	else
     72 		ud.u_fpscr |= INVBITS;
     73 	ud.u_fpscr &= ~STICKYBITS;
     74 	ud.u_fpscr |= ((uint32_t)mask << STICKYSHFT) & STICKYBITS;
     75 	/*
     76 	 * Make FPSCR_FX reflect the presence of a set sticky bit (or not).
     77 	 */
     78 	if (ud.u_fpscr & (STICKYBITS|INVBITS))
     79 		ud.u_fpscr |= FPSCR_FX;
     80 	else
     81 		ud.u_fpscr &= ~FPSCR_FX;
     82 	/*
     83 	 * Write back the fpscr.
     84 	 */
     85 	__asm volatile("mtfsf 0xff,%0" :: "f"(ud.u_d));
     86 	return (old);
     87 }
     88