round_xsig.s

内核linux2.4.20,可跟rtlinux3.2打补丁 组成实时linux系统,编译内核

/*---------------------------------------------------------------------------+
 |  round_Xsig.S                                                             |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1995                                         |
 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
 |                       Australia.  E-mail [e-mail] |
 |                                                                           |
 | Normalize and round a 12 byte quantity.                                   |
 | Call from C as:                                                           |
 |   int round_Xsig(Xsig *n)                                                 |
 |                                                                           |
 | Normalize a 12 byte quantity.                                             |
 | Call from C as:                                                           |
 |   int norm_Xsig(Xsig *n)                                                  |
 |                                                                           |
 | Each function returns the size of the shift (nr of bits).                 |
 |                                                                           |
 +---------------------------------------------------------------------------*/
	.file	"round_Xsig.S"

#include "fpu_emu.h"


.text
ENTRY(round_Xsig)
	pushl	%ebp
	movl	%esp,%ebp
	pushl	%ebx		/* Reserve some space */
	pushl	%ebx
	pushl	%esi

	movl	PARAM1,%esi

	movl	8(%esi),%edx
	movl	4(%esi),%ebx
	movl	(%esi),%eax

	movl	$0,-4(%ebp)

	orl	%edx,%edx	/* ms bits */
	js	L_round		/* Already normalized */
	jnz	L_shift_1	/* Shift left 1 - 31 bits */

	movl	%ebx,%edx
	movl	%eax,%ebx
	xorl	%eax,%eax
	movl	$-32,-4(%ebp)

/* We need to shift left by 1 - 31 bits */
L_shift_1:
	bsrl	%edx,%ecx	/* get the required shift in %ecx */
	subl	$31,%ecx
	negl	%ecx
	subl	%ecx,-4(%ebp)
	shld	%cl,%ebx,%edx
	shld	%cl,%eax,%ebx
	shl	%cl,%eax

L_round:
	testl	$0x80000000,%eax
	jz	L_exit

	addl	$1,%ebx
	adcl	$0,%edx
	jnz	L_exit

	movl	$0x80000000,%edx
	incl	-4(%ebp)

L_exit:
	movl	%edx,8(%esi)
	movl	%ebx,4(%esi)
	movl	%eax,(%esi)

	movl	-4(%ebp),%eax

	popl	%esi
	popl	%ebx
	leave
	ret




ENTRY(norm_Xsig)
	pushl	%ebp
	movl	%esp,%ebp
	pushl	%ebx		/* Reserve some space */
	pushl	%ebx
	pushl	%esi

	movl	PARAM1,%esi

	movl	8(%esi),%edx
	movl	4(%esi),%ebx
	movl	(%esi),%eax

	movl	$0,-4(%ebp)

	orl	%edx,%edx	/* ms bits */
	js	L_n_exit		/* Already normalized */
	jnz	L_n_shift_1	/* Shift left 1 - 31 bits */

	movl	%ebx,%edx
	movl	%eax,%ebx
	xorl	%eax,%eax
	movl	$-32,-4(%ebp)

	orl	%edx,%edx	/* ms bits */
	js	L_n_exit	/* Normalized now */
	jnz	L_n_shift_1	/* Shift left 1 - 31 bits */

	movl	%ebx,%edx
	movl	%eax,%ebx
	xorl	%eax,%eax
	addl	$-32,-4(%ebp)
	jmp	L_n_exit	/* Might not be normalized,
	                           but shift no more. */

/* We need to shift left by 1 - 31 bits */
L_n_shift_1:
	bsrl	%edx,%ecx	/* get the required shift in %ecx */
	subl	$31,%ecx
	negl	%ecx
	subl	%ecx,-4(%ebp)
	shld	%cl,%ebx,%edx
	shld	%cl,%eax,%ebx
	shl	%cl,%eax

L_n_exit:
	movl	%edx,8(%esi)
	movl	%ebx,4(%esi)
	movl	%eax,(%esi)

	movl	-4(%ebp),%eax

	popl	%esi
	popl	%ebx
	leave
	ret