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1da177e4 LT |
1 | /*---------------------------------------------------------------------------+ |
2 | | reg_norm.S | | |
3 | | | | |
4 | | Copyright (C) 1992,1993,1994,1995,1997 | | |
5 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, | | |
6 | | Australia. E-mail billm@suburbia.net | | |
7 | | | | |
8 | | Normalize the value in a FPU_REG. | | |
9 | | | | |
10 | | Call from C as: | | |
11 | | int FPU_normalize(FPU_REG *n) | | |
12 | | | | |
13 | | int FPU_normalize_nuo(FPU_REG *n) | | |
14 | | | | |
15 | | Return value is the tag of the answer, or-ed with FPU_Exception if | | |
16 | | one was raised, or -1 on internal error. | | |
17 | | | | |
18 | +---------------------------------------------------------------------------*/ | |
19 | ||
20 | #include "fpu_emu.h" | |
21 | ||
22 | ||
23 | .text | |
24 | ENTRY(FPU_normalize) | |
25 | pushl %ebp | |
26 | movl %esp,%ebp | |
27 | pushl %ebx | |
28 | ||
29 | movl PARAM1,%ebx | |
30 | ||
31 | movl SIGH(%ebx),%edx | |
32 | movl SIGL(%ebx),%eax | |
33 | ||
34 | orl %edx,%edx /* ms bits */ | |
35 | js L_done /* Already normalized */ | |
36 | jnz L_shift_1 /* Shift left 1 - 31 bits */ | |
37 | ||
38 | orl %eax,%eax | |
39 | jz L_zero /* The contents are zero */ | |
40 | ||
41 | movl %eax,%edx | |
42 | xorl %eax,%eax | |
43 | subw $32,EXP(%ebx) /* This can cause an underflow */ | |
44 | ||
45 | /* We need to shift left by 1 - 31 bits */ | |
46 | L_shift_1: | |
47 | bsrl %edx,%ecx /* get the required shift in %ecx */ | |
48 | subl $31,%ecx | |
49 | negl %ecx | |
50 | shld %cl,%eax,%edx | |
51 | shl %cl,%eax | |
52 | subw %cx,EXP(%ebx) /* This can cause an underflow */ | |
53 | ||
54 | movl %edx,SIGH(%ebx) | |
55 | movl %eax,SIGL(%ebx) | |
56 | ||
57 | L_done: | |
58 | cmpw EXP_OVER,EXP(%ebx) | |
59 | jge L_overflow | |
60 | ||
61 | cmpw EXP_UNDER,EXP(%ebx) | |
62 | jle L_underflow | |
63 | ||
64 | L_exit_valid: | |
65 | movl TAG_Valid,%eax | |
66 | ||
67 | /* Convert the exponent to 80x87 form. */ | |
68 | addw EXTENDED_Ebias,EXP(%ebx) | |
69 | andw $0x7fff,EXP(%ebx) | |
70 | ||
71 | L_exit: | |
72 | popl %ebx | |
73 | leave | |
74 | ret | |
75 | ||
76 | ||
77 | L_zero: | |
78 | movw $0,EXP(%ebx) | |
79 | movl TAG_Zero,%eax | |
80 | jmp L_exit | |
81 | ||
82 | L_underflow: | |
83 | /* Convert the exponent to 80x87 form. */ | |
84 | addw EXTENDED_Ebias,EXP(%ebx) | |
85 | push %ebx | |
86 | call arith_underflow | |
87 | pop %ebx | |
88 | jmp L_exit | |
89 | ||
90 | L_overflow: | |
91 | /* Convert the exponent to 80x87 form. */ | |
92 | addw EXTENDED_Ebias,EXP(%ebx) | |
93 | push %ebx | |
94 | call arith_overflow | |
95 | pop %ebx | |
96 | jmp L_exit | |
97 | ||
98 | ||
99 | ||
100 | /* Normalise without reporting underflow or overflow */ | |
101 | ENTRY(FPU_normalize_nuo) | |
102 | pushl %ebp | |
103 | movl %esp,%ebp | |
104 | pushl %ebx | |
105 | ||
106 | movl PARAM1,%ebx | |
107 | ||
108 | movl SIGH(%ebx),%edx | |
109 | movl SIGL(%ebx),%eax | |
110 | ||
111 | orl %edx,%edx /* ms bits */ | |
112 | js L_exit_nuo_valid /* Already normalized */ | |
113 | jnz L_nuo_shift_1 /* Shift left 1 - 31 bits */ | |
114 | ||
115 | orl %eax,%eax | |
116 | jz L_exit_nuo_zero /* The contents are zero */ | |
117 | ||
118 | movl %eax,%edx | |
119 | xorl %eax,%eax | |
120 | subw $32,EXP(%ebx) /* This can cause an underflow */ | |
121 | ||
122 | /* We need to shift left by 1 - 31 bits */ | |
123 | L_nuo_shift_1: | |
124 | bsrl %edx,%ecx /* get the required shift in %ecx */ | |
125 | subl $31,%ecx | |
126 | negl %ecx | |
127 | shld %cl,%eax,%edx | |
128 | shl %cl,%eax | |
129 | subw %cx,EXP(%ebx) /* This can cause an underflow */ | |
130 | ||
131 | movl %edx,SIGH(%ebx) | |
132 | movl %eax,SIGL(%ebx) | |
133 | ||
134 | L_exit_nuo_valid: | |
135 | movl TAG_Valid,%eax | |
136 | ||
137 | popl %ebx | |
138 | leave | |
139 | ret | |
140 | ||
141 | L_exit_nuo_zero: | |
142 | movl TAG_Zero,%eax | |
143 | movw EXP_UNDER,EXP(%ebx) | |
144 | ||
145 | popl %ebx | |
146 | leave | |
147 | ret |