xref: /openbmc/linux/arch/x86/math-emu/reg_u_mul.S (revision 14b476e0)
1/* SPDX-License-Identifier: GPL-2.0 */
2	.file	"reg_u_mul.S"
3/*---------------------------------------------------------------------------+
4 |  reg_u_mul.S                                                              |
5 |                                                                           |
6 | Core multiplication routine                                               |
7 |                                                                           |
8 | Copyright (C) 1992,1993,1995,1997                                         |
9 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
10 |                  E-mail   billm@suburbia.net                              |
11 |                                                                           |
12 |                                                                           |
13 +---------------------------------------------------------------------------*/
14
15/*---------------------------------------------------------------------------+
16 |   Basic multiplication routine.                                           |
17 |   Does not check the resulting exponent for overflow/underflow            |
18 |                                                                           |
19 |   FPU_u_mul(FPU_REG *a, FPU_REG *b, FPU_REG *c, unsigned int cw);         |
20 |                                                                           |
21 |   Internal working is at approx 128 bits.                                 |
22 |   Result is rounded to nearest 53 or 64 bits, using "nearest or even".    |
23 +---------------------------------------------------------------------------*/
24
25#include "exception.h"
26#include "fpu_emu.h"
27#include "control_w.h"
28
29
30
31#ifndef NON_REENTRANT_FPU
32/*  Local storage on the stack: */
33#define FPU_accum_0	-4(%ebp)	/* ms word */
34#define FPU_accum_1	-8(%ebp)
35
36#else
37/*  Local storage in a static area: */
38.data
39	.align 4,0
40FPU_accum_0:
41	.long	0
42FPU_accum_1:
43	.long	0
44#endif /* NON_REENTRANT_FPU */
45
46
47.text
48SYM_FUNC_START(FPU_u_mul)
49	pushl	%ebp
50	movl	%esp,%ebp
51#ifndef NON_REENTRANT_FPU
52	subl	$8,%esp
53#endif /* NON_REENTRANT_FPU */
54
55	pushl	%esi
56	pushl	%edi
57	pushl	%ebx
58
59	movl	PARAM1,%esi
60	movl	PARAM2,%edi
61
62#ifdef PARANOID
63	testl	$0x80000000,SIGH(%esi)
64	jz	L_bugged
65	testl	$0x80000000,SIGH(%edi)
66	jz	L_bugged
67#endif /* PARANOID */
68
69	xorl	%ecx,%ecx
70	xorl	%ebx,%ebx
71
72	movl	SIGL(%esi),%eax
73	mull	SIGL(%edi)
74	movl	%eax,FPU_accum_0
75	movl	%edx,FPU_accum_1
76
77	movl	SIGL(%esi),%eax
78	mull	SIGH(%edi)
79	addl	%eax,FPU_accum_1
80	adcl	%edx,%ebx
81/*	adcl	$0,%ecx		// overflow here is not possible */
82
83	movl	SIGH(%esi),%eax
84	mull	SIGL(%edi)
85	addl	%eax,FPU_accum_1
86	adcl	%edx,%ebx
87	adcl	$0,%ecx
88
89	movl	SIGH(%esi),%eax
90	mull	SIGH(%edi)
91	addl	%eax,%ebx
92	adcl	%edx,%ecx
93
94	/* Get the sum of the exponents. */
95	movl	PARAM6,%eax
96	subl	EXP_BIAS-1,%eax
97
98	/* Two denormals can cause an exponent underflow */
99	cmpl	EXP_WAY_UNDER,%eax
100	jg	Exp_not_underflow
101
102	/* Set to a really low value allow correct handling */
103	movl	EXP_WAY_UNDER,%eax
104
105Exp_not_underflow:
106
107/*  Have now finished with the sources */
108	movl	PARAM3,%edi	/* Point to the destination */
109	movw	%ax,EXP(%edi)
110
111/*  Now make sure that the result is normalized */
112	testl	$0x80000000,%ecx
113	jnz	LResult_Normalised
114
115	/* Normalize by shifting left one bit */
116	shll	$1,FPU_accum_0
117	rcll	$1,FPU_accum_1
118	rcll	$1,%ebx
119	rcll	$1,%ecx
120	decw	EXP(%edi)
121
122LResult_Normalised:
123	movl	FPU_accum_0,%eax
124	movl	FPU_accum_1,%edx
125	orl	%eax,%eax
126	jz	L_extent_zero
127
128	orl	$1,%edx
129
130L_extent_zero:
131	movl	%ecx,%eax
132	jmp	fpu_reg_round
133
134
135#ifdef PARANOID
136L_bugged:
137	pushl	EX_INTERNAL|0x205
138	call	EXCEPTION
139	pop	%ebx
140	jmp	L_exit
141
142L_exit:
143	popl	%ebx
144	popl	%edi
145	popl	%esi
146	leave
147	RET
148#endif /* PARANOID */
149
150SYM_FUNC_END(FPU_u_mul)
151