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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/x86/math-emu/fpu_etc.c
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// SPDX-License-Identifier: GPL-2.0

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/*---------------------------------------------------------------------------+

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 |  fpu_etc.c                                                                |

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 |                                                                           |

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 | Implement a few FPU instructions.                                         |

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 |                                                                           |

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 | Copyright (C) 1992,1993,1994,1997                                         |

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 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |

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 |                       Australia.  E-mail   [email protected]             |

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 |                                                                           |

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 |                                                                           |

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 +---------------------------------------------------------------------------*/

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#include "fpu_system.h"

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#include "exception.h"

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#include "fpu_emu.h"

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#include "status_w.h"

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#include "reg_constant.h"

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static void fchs(FPU_REG *st0_ptr, u_char st0tag)

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{

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	if (st0tag ^ TAG_Empty) {

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		signbyte(st0_ptr) ^= SIGN_NEG;

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		clear_C1();

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	} else

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		FPU_stack_underflow();

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}

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static void fabs(FPU_REG *st0_ptr, u_char st0tag)

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{

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	if (st0tag ^ TAG_Empty) {

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		setpositive(st0_ptr);

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		clear_C1();

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	} else

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		FPU_stack_underflow();

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}

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static void ftst_(FPU_REG *st0_ptr, u_char st0tag)

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{

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	switch (st0tag) {

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	case TAG_Zero:

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		setcc(SW_C3);

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		break;

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	case TAG_Valid:

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		if (getsign(st0_ptr) == SIGN_POS)

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			setcc(0);

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		else

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			setcc(SW_C0);

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		break;

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	case TAG_Special:

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		switch (FPU_Special(st0_ptr)) {

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		case TW_Denormal:

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			if (getsign(st0_ptr) == SIGN_POS)

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				setcc(0);

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			else

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				setcc(SW_C0);

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			if (denormal_operand() < 0) {

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#ifdef PECULIAR_486

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				/* This is weird! */

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				if (getsign(st0_ptr) == SIGN_POS)

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					setcc(SW_C3);

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#endif /* PECULIAR_486 */

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				return;

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			}

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			break;

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		case TW_NaN:

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			setcc(SW_C0 | SW_C2 | SW_C3);	/* Operand is not comparable */

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			EXCEPTION(EX_Invalid);

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			break;

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		case TW_Infinity:

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			if (getsign(st0_ptr) == SIGN_POS)

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				setcc(0);

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			else

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				setcc(SW_C0);

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			break;

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		default:

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			setcc(SW_C0 | SW_C2 | SW_C3);	/* Operand is not comparable */

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			EXCEPTION(EX_INTERNAL | 0x14);

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			break;

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		}

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		break;

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	case TAG_Empty:

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		setcc(SW_C0 | SW_C2 | SW_C3);

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		EXCEPTION(EX_StackUnder);

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		break;

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	}

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}

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static void fxam(FPU_REG *st0_ptr, u_char st0tag)

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{

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	int c = 0;

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	switch (st0tag) {

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	case TAG_Empty:

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		c = SW_C3 | SW_C0;

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		break;

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	case TAG_Zero:

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		c = SW_C3;

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		break;

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	case TAG_Valid:

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		c = SW_C2;

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		break;

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	case TAG_Special:

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		switch (FPU_Special(st0_ptr)) {

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		case TW_Denormal:

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			c = SW_C2 | SW_C3;	/* Denormal */

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			break;

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		case TW_NaN:

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			/* We also use NaN for unsupported types. */

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			if ((st0_ptr->sigh & 0x80000000)

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			    && (exponent(st0_ptr) == EXP_OVER))

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				c = SW_C0;

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			break;

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		case TW_Infinity:

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			c = SW_C2 | SW_C0;

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			break;

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		}

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	}

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	if (getsign(st0_ptr) == SIGN_NEG)

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		c |= SW_C1;

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	setcc(c);

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}

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static void FPU_ST0_illegal(FPU_REG *st0_ptr, u_char st0_tag)

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{

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	FPU_illegal();

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}

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static FUNC_ST0 const fp_etc_table[] = {

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	fchs, fabs, FPU_ST0_illegal, FPU_ST0_illegal,

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	ftst_, fxam, FPU_ST0_illegal, FPU_ST0_illegal,

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};

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void FPU_etc(void)

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{

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	(fp_etc_table[FPU_rm]) (&st(0), FPU_gettag0());

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}

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