xref: /openbmc/linux/arch/x86/math-emu/reg_norm.S (revision dd21bfa4) 
1/* SPDX-License-Identifier: GPL-2.0 */
2/*---------------------------------------------------------------------------+
3 |  reg_norm.S                                                               |
4 |                                                                           |
5 | Copyright (C) 1992,1993,1994,1995,1997                                    |
6 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
7 |                       Australia.  E-mail billm@suburbia.net               |
8 |                                                                           |
9 | Normalize the value in a FPU_REG.                                         |
10 |                                                                           |
11 | Call from C as:                                                           |
12 |    int FPU_normalize(FPU_REG *n)                                          |
13 |                                                                           |
14 |    int FPU_normalize_nuo(FPU_REG *n)                                      |
15 |                                                                           |
16 |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
17 |    one was raised, or -1 on internal error.                               |
18 |                                                                           |
19 +---------------------------------------------------------------------------*/
20
21#include "fpu_emu.h"
22
23
24.text
25SYM_FUNC_START(FPU_normalize)
26	pushl	%ebp
27	movl	%esp,%ebp
28	pushl	%ebx
29
30	movl	PARAM1,%ebx
31
32	movl	SIGH(%ebx),%edx
33	movl	SIGL(%ebx),%eax
34
35	orl	%edx,%edx	/* ms bits */
36	js	L_done		/* Already normalized */
37	jnz	L_shift_1	/* Shift left 1 - 31 bits */
38
39	orl	%eax,%eax
40	jz	L_zero		/* The contents are zero */
41
42	movl	%eax,%edx
43	xorl	%eax,%eax
44	subw	$32,EXP(%ebx)	/* This can cause an underflow */
45
46/* We need to shift left by 1 - 31 bits */
47L_shift_1:
48	bsrl	%edx,%ecx	/* get the required shift in %ecx */
49	subl	$31,%ecx
50	negl	%ecx
51	shld	%cl,%eax,%edx
52	shl	%cl,%eax
53	subw	%cx,EXP(%ebx)	/* This can cause an underflow */
54
55	movl	%edx,SIGH(%ebx)
56	movl	%eax,SIGL(%ebx)
57
58L_done:
59	cmpw	EXP_OVER,EXP(%ebx)
60	jge	L_overflow
61
62	cmpw	EXP_UNDER,EXP(%ebx)
63	jle	L_underflow
64
65L_exit_valid:
66	movl	TAG_Valid,%eax
67
68	/* Convert the exponent to 80x87 form. */
69	addw	EXTENDED_Ebias,EXP(%ebx)
70	andw	$0x7fff,EXP(%ebx)
71
72L_exit:
73	popl	%ebx
74	leave
75	RET
76
77
78L_zero:
79	movw	$0,EXP(%ebx)
80	movl	TAG_Zero,%eax
81	jmp	L_exit
82
83L_underflow:
84	/* Convert the exponent to 80x87 form. */
85	addw	EXTENDED_Ebias,EXP(%ebx)
86	push	%ebx
87	call	arith_underflow
88	pop	%ebx
89	jmp	L_exit
90
91L_overflow:
92	/* Convert the exponent to 80x87 form. */
93	addw	EXTENDED_Ebias,EXP(%ebx)
94	push	%ebx
95	call	arith_overflow
96	pop	%ebx
97	jmp	L_exit
98SYM_FUNC_END(FPU_normalize)
99
100
101
102/* Normalise without reporting underflow or overflow */
103SYM_FUNC_START(FPU_normalize_nuo)
104	pushl	%ebp
105	movl	%esp,%ebp
106	pushl	%ebx
107
108	movl	PARAM1,%ebx
109
110	movl	SIGH(%ebx),%edx
111	movl	SIGL(%ebx),%eax
112
113	orl	%edx,%edx	/* ms bits */
114	js	L_exit_nuo_valid	/* Already normalized */
115	jnz	L_nuo_shift_1	/* Shift left 1 - 31 bits */
116
117	orl	%eax,%eax
118	jz	L_exit_nuo_zero		/* The contents are zero */
119
120	movl	%eax,%edx
121	xorl	%eax,%eax
122	subw	$32,EXP(%ebx)	/* This can cause an underflow */
123
124/* We need to shift left by 1 - 31 bits */
125L_nuo_shift_1:
126	bsrl	%edx,%ecx	/* get the required shift in %ecx */
127	subl	$31,%ecx
128	negl	%ecx
129	shld	%cl,%eax,%edx
130	shl	%cl,%eax
131	subw	%cx,EXP(%ebx)	/* This can cause an underflow */
132
133	movl	%edx,SIGH(%ebx)
134	movl	%eax,SIGL(%ebx)
135
136L_exit_nuo_valid:
137	movl	TAG_Valid,%eax
138
139	popl	%ebx
140	leave
141	RET
142
143L_exit_nuo_zero:
144	movl	TAG_Zero,%eax
145	movw	EXP_UNDER,EXP(%ebx)
146
147	popl	%ebx
148	leave
149	RET
150SYM_FUNC_END(FPU_normalize_nuo)
151