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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/x86/math-emu/reg_u_mul.S
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	.file	"reg_u_mul.S"

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

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 |  reg_u_mul.S                                                              |

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 |                                                                           |

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 | Core multiplication routine                                               |

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 |                                                                           |

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 | Copyright (C) 1992,1993,1995,1997                                         |

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

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 |                  E-mail   [email protected]                              |

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 |                                                                           |

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 |                                                                           |

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

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

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 |   Basic multiplication routine.                                           |

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 |   Does not check the resulting exponent for overflow/underflow            |

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 |                                                                           |

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 |   FPU_u_mul(FPU_REG *a, FPU_REG *b, FPU_REG *c, unsigned int cw);         |

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 |                                                                           |

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 |   Internal working is at approx 128 bits.                                 |

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 |   Result is rounded to nearest 53 or 64 bits, using "nearest or even".    |

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

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#include "exception.h"

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#include "fpu_emu.h"

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#include "control_w.h"

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#ifndef NON_REENTRANT_FPU

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/*  Local storage on the stack: */

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#define FPU_accum_0	-4(%ebp)	/* ms word */

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#define FPU_accum_1	-8(%ebp)

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#else

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/*  Local storage in a static area: */

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.data

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	.align 4,0

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FPU_accum_0:

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	.long	0

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FPU_accum_1:

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	.long	0

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#endif /* NON_REENTRANT_FPU */

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.text

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ENTRY(FPU_u_mul)

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	pushl	%ebp

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	movl	%esp,%ebp

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#ifndef NON_REENTRANT_FPU

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	subl	$8,%esp

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#endif /* NON_REENTRANT_FPU */ 

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	pushl	%esi

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	pushl	%edi

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	pushl	%ebx

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	movl	PARAM1,%esi

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	movl	PARAM2,%edi

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#ifdef PARANOID

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	testl	$0x80000000,SIGH(%esi)

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	jz	L_bugged

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	testl	$0x80000000,SIGH(%edi)

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	jz	L_bugged

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#endif /* PARANOID */

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	xorl	%ecx,%ecx

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	xorl	%ebx,%ebx

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	movl	SIGL(%esi),%eax

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	mull	SIGL(%edi)

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	movl	%eax,FPU_accum_0

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	movl	%edx,FPU_accum_1

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	movl	SIGL(%esi),%eax

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	mull	SIGH(%edi)

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	addl	%eax,FPU_accum_1

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	adcl	%edx,%ebx

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/*	adcl	$0,%ecx		// overflow here is not possible */

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	movl	SIGH(%esi),%eax

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	mull	SIGL(%edi)

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	addl	%eax,FPU_accum_1

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	adcl	%edx,%ebx

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	adcl	$0,%ecx

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	movl	SIGH(%esi),%eax

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	mull	SIGH(%edi)

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	addl	%eax,%ebx

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	adcl	%edx,%ecx

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	/* Get the sum of the exponents. */

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	movl	PARAM6,%eax

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	subl	EXP_BIAS-1,%eax

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	/* Two denormals can cause an exponent underflow */

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	cmpl	EXP_WAY_UNDER,%eax

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	jg	Exp_not_underflow

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	/* Set to a really low value allow correct handling */

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	movl	EXP_WAY_UNDER,%eax

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Exp_not_underflow:

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/*  Have now finished with the sources */

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	movl	PARAM3,%edi	/* Point to the destination */

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	movw	%ax,EXP(%edi)

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/*  Now make sure that the result is normalized */

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	testl	$0x80000000,%ecx

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	jnz	LResult_Normalised

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	/* Normalize by shifting left one bit */

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	shll	$1,FPU_accum_0

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	rcll	$1,FPU_accum_1

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	rcll	$1,%ebx

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	rcll	$1,%ecx

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	decw	EXP(%edi)

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LResult_Normalised:

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	movl	FPU_accum_0,%eax

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	movl	FPU_accum_1,%edx

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	orl	%eax,%eax

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	jz	L_extent_zero

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	orl	$1,%edx

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L_extent_zero:

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	movl	%ecx,%eax

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	jmp	fpu_reg_round

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#ifdef PARANOID

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L_bugged:

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	pushl	EX_INTERNAL|0x205

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	call	EXCEPTION

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	pop	%ebx

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	jmp	L_exit

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L_exit:

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	popl	%ebx

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	popl	%edi

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	popl	%esi

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	leave

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	ret

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#endif /* PARANOID */ 

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