xref: /src/sys/arch/m68k/fpe/fpu_fscale.c

/*	$NetBSD: fpu_fscale.c,v 1.17 2025/01/06 07:34:24 isaki Exp $	*/

/*
 * Copyright (c) 1995 Ken Nakata
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 * 4. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Gordon Ross
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * FSCALE - separated from the other type0 arithmetic instructions
 * for performance reason; maybe unnecessary, but FSCALE assumes
 * the source operand be an integer.  It performs type conversion
 * only if the source operand is *not* an integer.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: fpu_fscale.c,v 1.17 2025/01/06 07:34:24 isaki Exp $");

#include <sys/types.h>
#include <sys/signal.h>
#include <sys/systm.h>
#include <machine/frame.h>

#include "fpu_emulate.h"

int
fpu_emul_fscale(struct fpemu *fe, struct instruction *insn)
{
	struct frame *frame;
	uint32_t *fpregs;
	int word1, sig;
	int regnum, format;
	int modreg;
	int scale, sign, exp;
	uint32_t m0, m1;
	uint32_t buf[3], fpsr;
#if DEBUG_FPE
	int flags;
	char regname;
#endif

	scale = sig = 0;
	frame = fe->fe_frame;
	fpregs = &(fe->fe_fpframe->fpf_regs[0]);
	/* clear all exceptions and conditions */
	fpsr = fe->fe_fpsr & ~FPSR_EXCP & ~FPSR_CCB;
#if DEBUG_FPE
	printf("fpu_emul_fscale: FPSR = %08x, FPCR = %08x\n", fpsr, fe->fe_fpcr);
#endif

	word1 = insn->is_word1;
	format = (word1 >> 10) & 7;
	regnum = (word1 >> 7) & 7;

	fe->fe_fpcr &= FPCR_ROUND;
	fe->fe_fpcr |= FPCR_ZERO;

	/* get the source operand */
	if ((word1 & 0x4000) == 0) {
#if DEBUG_FPE
		printf("fpu_emul_fscale: FP%d op FP%d => FP%d\n",
		    format, regnum, regnum);
		/* the operand is an FP reg */
		printf("fpu_emul_scale: src opr FP%d=%08x%08x%08x\n",
		    format, fpregs[format*3], fpregs[format*3+1],
		    fpregs[format*3+2]);
#endif
		fpu_explode(fe, &fe->fe_f2, FTYPE_EXT, &fpregs[format * 3]);
		fpu_implode(fe, &fe->fe_f2, FTYPE_LNG, buf);
		scale = buf[0];
	} else {
		/* the operand is in memory */
		if (format == FTYPE_DBL) {
			insn->is_datasize = 8;
		} else if (format == FTYPE_SNG || format == FTYPE_LNG) {
			insn->is_datasize = 4;
		} else if (format == FTYPE_WRD) {
			insn->is_datasize = 2;
		} else if (format == FTYPE_BYT) {
			insn->is_datasize = 1;
		} else if (format == FTYPE_EXT) {
			insn->is_datasize = 12;
		} else {
			/* invalid or unsupported operand format */
			sig = SIGFPE;
			return sig;
		}

		/* Check an illegal mod/reg. */
		modreg = insn->is_opcode & 077;
		if ((modreg >> 3) == 1/*An*/ || modreg >= 075) {
			return SIGILL;
		}

		/* Get effective address. (modreg=opcode&077) */
		sig = fpu_decode_ea(frame, insn, &insn->is_ea, insn->is_opcode);
		if (sig) {
#if DEBUG_FPE
			printf("fpu_emul_fscale: error in decode_ea\n");
#endif
			return sig;
		}

		if (insn->is_ea.ea_flags == EA_DIRECT &&
		    insn->is_datasize > 4) {
#if DEBUG_FPE
			printf("%s: attempted to fetch dbl/ext from reg\n",
			    __func__);
#endif
			return SIGILL;
		}

#if DEBUG_FPE
		printf("fpu_emul_fscale: addr mode = ");
		flags = insn->is_ea.ea_flags;
		regname = (insn->is_ea.ea_regnum & 8) ? 'a' : 'd';

		if (flags & EA_DIRECT) {
			printf("%c%d\n", regname, insn->is_ea.ea_regnum & 7);
		} else if (flags & EA_PREDECR) {
			printf("%c%d@-\n", regname, insn->is_ea.ea_regnum & 7);
		} else if (flags & EA_POSTINCR) {
			printf("%c%d@+\n", regname, insn->is_ea.ea_regnum & 7);
		} else if (flags & EA_OFFSET) {
			printf("%c%d@(%d)\n",
			    regname, insn->is_ea.ea_regnum & 7,
			    insn->is_ea.ea_offset);
		} else if (flags & EA_INDEXED) {
			printf("%c%d@(...)\n",
			    regname, insn->is_ea.ea_regnum & 7);
		} else if (flags & EA_ABS) {
			printf("0x%08x\n", insn->is_ea.ea_absaddr);
		} else if (flags & EA_PC_REL) {
			printf("pc@(%d)\n", insn->is_ea.ea_offset);
		} else if (flags & EA_IMMED) {
			printf("#0x%08x%08x%08x\n",
			    insn->is_ea.ea_immed[0],
			    insn->is_ea.ea_immed[1],
			    insn->is_ea.ea_immed[2]);
		} else {
			printf("%c%d@\n", regname, insn->is_ea.ea_regnum & 7);
		}
#endif
		fpu_load_ea(frame, insn, &insn->is_ea, (char*)buf);

#if DEBUG_FPE
		printf("fpu_emul_fscale: src = %08x%08x%08x, siz = %d\n",
		    buf[0], buf[1], buf[2], insn->is_datasize);
#endif
		if (format == FTYPE_LNG) {
			/* nothing */
			scale = buf[0];
		} else if (format == FTYPE_WRD) {
			/* sign-extend */
			scale = buf[0] & 0xffff;
			if (scale & 0x8000) {
				scale |= 0xffff0000;
			}
		} else if (format == FTYPE_BYT) {
			/* sign-extend */
			scale = buf[0] & 0xff;
			if (scale & 0x80) {
				scale |= 0xffffff00;
			}
		} else if (format == FTYPE_DBL || format == FTYPE_SNG ||
		           format == FTYPE_EXT) {
			fpu_explode(fe, &fe->fe_f2, format, buf);
			fpu_implode(fe, &fe->fe_f2, FTYPE_LNG, buf);
			scale = buf[0];
		}
		/* make it look like we've got an FP oprand */
		fe->fe_f2.fp_class = (buf[0] == 0) ? FPC_ZERO : FPC_NUM;
	}

	/* assume there's no exception */
	sig = 0;

	/*
	 * it's barbaric but we're going to operate directly on
	 * the dst operand's bit pattern
	 */
	sign = fpregs[regnum * 3] & 0x80000000;
	exp = (fpregs[regnum * 3] & 0x7fff0000) >> 16;
	m0 = fpregs[regnum * 3 + 1];
	m1 = fpregs[regnum * 3 + 2];

	switch (fe->fe_f2.fp_class) {
	case FPC_SNAN:
		fpsr |= FPSR_SNAN;
	case FPC_QNAN:
		/* dst = NaN */
		exp = 0x7fff;
		m0 = m1 = 0xffffffff;
		break;
	case FPC_ZERO:
	case FPC_NUM:
		if ((0 < exp && exp < 0x7fff) ||
		    (exp == 0 && (m0 | m1) != 0)) {
			/* normal or denormal */
			exp += scale;
			if (exp < 0) {
				/* underflow */
				uint32_t grs;	/* guard, round and sticky */

				exp = 0;
				grs = m1 << (32 + exp);
				m1 = m0 << (32 + exp) | m1 >> -exp;
				m0 >>= -exp;
				if (grs != 0) {
					fpsr |= FPSR_INEX2;

					switch (fe->fe_fpcr & 0x30) {
					case FPCR_MINF:
						if (sign != 0) {
							if (++m1 == 0 &&
							    ++m0 == 0) {
								m0 = 0x80000000;
								exp++;
							}
						}
						break;
					case FPCR_NEAR:
						if (grs == 0x80000000) {
							/* tie */
							if ((m1 & 1) &&
							    ++m1 == 0 &&
							    ++m0 == 0) {
								m0 = 0x80000000;
								exp++;
							}
						} else if (grs & 0x80000000) {
							if (++m1 == 0 &&
							    ++m0 == 0) {
								m0 = 0x80000000;
								exp++;
							}
						}
						break;
					case FPCR_PINF:
						if (sign == 0) {
							if (++m1 == 0 &&
							    ++m0 == 0) {
								m0 = 0x80000000;
								exp++;
							}
						}
						break;
					case FPCR_ZERO:
						break;
					}
				}
				if (exp == 0 && (m0 & 0x80000000) == 0) {
					fpsr |= FPSR_UNFL;
					if ((m0 | m1) == 0) {
						fpsr |= FPSR_ZERO;
					}
				}
			} else if (exp >= 0x7fff) {
				/* overflow --> result = Inf */
				/*
				 * but first, try to normalize in case it's an
				 * unnormalized
				 */
				while ((m0 & 0x80000000) == 0) {
					exp--;
					m0 = (m0 << 1) | (m1 >> 31);
					m1 = m1 << 1;
				}
				/* if it's still too large, then return Inf */
				if (exp >= 0x7fff) {
					exp = 0x7fff;
					m0 = m1 = 0;
					fpsr |= FPSR_OVFL | FPSR_INF;
				}
			} else if ((m0 & 0x80000000) == 0) {
				/*
				 * it's a denormal; we try to normalize but
				 * result may and may not be a normal.
				 */
				while (exp > 0 && (m0 & 0x80000000) == 0) {
					exp--;
					m0 = (m0 << 1) | (m1 >> 31);
					m1 = m1 << 1;
				}
				if ((m0 & 0x80000000) == 0) {
					fpsr |= FPSR_UNFL;
				}
			} /* exp in range and mantissa normalized */
		} else if (exp == 0 && m0 == 0 && m1 == 0) {
			/* dst is Zero */
			fpsr |= FPSR_ZERO;
		} /* else we know exp == 0x7fff */
		else if ((m0 | m1) == 0) {
			fpsr |= FPSR_INF;
		} else if ((m0 & 0x40000000) == 0) {
			/* a signaling NaN */
			fpsr |= FPSR_NAN | FPSR_SNAN;
		} else {
			/* a quiet NaN */
			fpsr |= FPSR_NAN;
		}
		break;
	case FPC_INF:
		/* dst = NaN */
		exp = 0x7fff;
		m0 = m1 = 0xffffffff;
		fpsr |= FPSR_OPERR | FPSR_NAN;
		break;
	default:
#ifdef DEBUG
		panic("fpu_emul_fscale: invalid fp class");
#endif
		break;
	}

	/* store the result */
	fpregs[regnum * 3] = sign | (exp << 16);
	fpregs[regnum * 3 + 1] = m0;
	fpregs[regnum * 3 + 2] = m1;

	if (sign) {
		fpsr |= FPSR_NEG;
	}

	/* update fpsr according to the result of operation */
	fe->fe_fpframe->fpf_fpsr = fe->fe_fpsr = fpsr;

#if DEBUG_FPE
	printf("fpu_emul_fscale: FPSR = %08x, FPCR = %08x\n",
	    fe->fe_fpsr, fe->fe_fpcr);
#endif

	return (fpsr & fe->fe_fpcr & FPSR_EXCP) ? SIGFPE : sig;
}