CoCalc -- reg_u

GitHub Repository: awilliam/linux-vfio
Path: blob/master/arch/x86/math-emu/reg_u_add.S
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	.file	"reg_u_add.S"
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/*---------------------------------------------------------------------------+
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 |  reg_u_add.S                                                              |
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 |                                                                           |
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 | Add two valid (TAG_Valid) FPU_REG numbers, of the same sign, and put the  |
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 |   result in a destination FPU_REG.                                        |
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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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 | Call from C as:                                                           |
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 |   int  FPU_u_add(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ,             |
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 |                                                int control_w)             |
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 |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
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 |    one was raised, or -1 on internal error.                               |
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 |                                                                           |
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 +---------------------------------------------------------------------------*/
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/*
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 |    Kernel addition routine FPU_u_add(reg *arg1, reg *arg2, reg *answ).
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 |    Takes two valid reg f.p. numbers (TAG_Valid), which are
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 |    treated as unsigned numbers,
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 |    and returns their sum as a TAG_Valid or TAG_Special f.p. number.
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 |    The returned number is normalized.
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 |    Basic checks are performed if PARANOID is defined.
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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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.text
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ENTRY(FPU_u_add)
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	pushl	%ebp
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	movl	%esp,%ebp
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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		/* source 1 */
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	movl	PARAM2,%edi		/* source 2 */
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	movl	PARAM6,%ecx
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	movl	%ecx,%edx
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	subl	PARAM7,%ecx			/* exp1 - exp2 */
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	jge	L_arg1_larger
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	/* num1 is smaller */
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	movl	SIGL(%esi),%ebx
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	movl	SIGH(%esi),%eax
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	movl	%edi,%esi
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	movl	PARAM7,%edx
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	negw	%cx
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	jmp	L_accum_loaded
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L_arg1_larger:
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	/* num1 has larger or equal exponent */
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	movl	SIGL(%edi),%ebx
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	movl	SIGH(%edi),%eax
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L_accum_loaded:
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	movl	PARAM3,%edi		/* destination */
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	movw	%dx,EXP(%edi)		/* Copy exponent to destination */
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	xorl	%edx,%edx		/* clear the extension */
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#ifdef PARANOID
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	testl	$0x80000000,%eax
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	je	L_bugged
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	testl	$0x80000000,SIGH(%esi)
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	je	L_bugged
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#endif /* PARANOID */
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/* The number to be shifted is in %eax:%ebx:%edx */
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	cmpw	$32,%cx		/* shrd only works for 0..31 bits */
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	jnc	L_more_than_31
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/* less than 32 bits */
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	shrd	%cl,%ebx,%edx
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	shrd	%cl,%eax,%ebx
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	shr	%cl,%eax
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	jmp	L_shift_done
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L_more_than_31:
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	cmpw	$64,%cx
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	jnc	L_more_than_63
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	subb	$32,%cl
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	jz	L_exactly_32
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	shrd	%cl,%eax,%edx
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	shr	%cl,%eax
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	orl	%ebx,%ebx
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	jz	L_more_31_no_low	/* none of the lowest bits is set */
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	orl	$1,%edx			/* record the fact in the extension */
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L_more_31_no_low:
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	movl	%eax,%ebx
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	xorl	%eax,%eax
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	jmp	L_shift_done
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L_exactly_32:
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	movl	%ebx,%edx
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	movl	%eax,%ebx
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	xorl	%eax,%eax
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	jmp	L_shift_done
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L_more_than_63:
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	cmpw	$65,%cx
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	jnc	L_more_than_64
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	movl	%eax,%edx
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	orl	%ebx,%ebx
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	jz	L_more_63_no_low
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	orl	$1,%edx
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	jmp	L_more_63_no_low
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L_more_than_64:
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	movl	$1,%edx		/* The shifted nr always at least one '1' */
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L_more_63_no_low:
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	xorl	%ebx,%ebx
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	xorl	%eax,%eax
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L_shift_done:
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	/* Now do the addition */
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	addl	SIGL(%esi),%ebx
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	adcl	SIGH(%esi),%eax
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	jnc	L_round_the_result
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	/* Overflow, adjust the result */
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	rcrl	$1,%eax
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	rcrl	$1,%ebx
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	rcrl	$1,%edx
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	jnc	L_no_bit_lost
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	orl	$1,%edx
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L_no_bit_lost:
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	incw	EXP(%edi)
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L_round_the_result:
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	jmp	fpu_reg_round	/* Round the result */
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#ifdef PARANOID
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/* If we ever get here then we have problems! */
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L_bugged:
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	pushl	EX_INTERNAL|0x201
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	call	EXCEPTION
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	pop	%ebx
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	movl	$-1,%eax
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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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