2823a4c8 |
1 | #include <stdio.h>\r |
2 | \r |
3 | typedef unsigned int u32;\r |
4 | \r |
5 | u32 arm_imm_find_nonzero(u32 imm, u32 start_bit)\r |
6 | {\r |
7 | u32 i;\r |
8 | \r |
9 | for(i = start_bit; i < 32; i += 2)\r |
10 | {\r |
11 | if((imm >> i) & 0x03)\r |
12 | break;\r |
13 | }\r |
14 | \r |
15 | return i;\r |
16 | }\r |
17 | \r |
18 | u32 arm_disect_imm_32bit(u32 imm, u32 *stores, u32 *rotations)\r |
19 | {\r |
20 | u32 store_count = 0;\r |
21 | u32 left_shift = 0;\r |
22 | \r |
23 | // Otherwise it'll return 0 things to store because it'll never\r |
24 | // find anything.\r |
25 | if(imm == 0)\r |
26 | {\r |
27 | rotations[0] = 0;\r |
28 | stores[0] = 0;\r |
29 | return 1;\r |
30 | }\r |
31 | \r |
32 | // Find chunks of non-zero data at 2 bit alignments.\r |
33 | while(1)\r |
34 | {\r |
35 | left_shift = arm_imm_find_nonzero(imm, left_shift);\r |
36 | \r |
37 | if(left_shift == 32)\r |
38 | {\r |
39 | // We've hit the end of the useful data.\r |
40 | return store_count;\r |
41 | }\r |
42 | \r |
43 | // Hit the end, it might wrap back around to the beginning.\r |
44 | if(left_shift >= 24)\r |
45 | {\r |
46 | // Make a mask for the residual bits. IE, if we have\r |
47 | // 5 bits of data at the end we can wrap around to 3\r |
48 | // bits of data in the beginning. Thus the first\r |
49 | // thing, after being shifted left, has to be less\r |
50 | // than 111b, 0x7, or (1 << 3) - 1.\r |
51 | u32 top_bits = 32 - left_shift;\r |
52 | u32 residual_bits = 8 - top_bits;\r |
53 | u32 residual_mask = (1 << residual_bits) - 1;\r |
54 | \r |
55 | if((store_count > 1) && (left_shift > 24) &&\r |
56 | ((stores[0] << (32 - rotations[0])) < residual_mask))\r |
57 | {\r |
58 | // Then we can throw out the last bit and tack it on\r |
59 | // to the first bit.\r |
60 | u32 initial_bits = rotations[0];\r |
61 | stores[0] = (stores[0] << (top_bits + (32 - rotations[0]))) |\r |
62 | ((imm >> left_shift) & 0xFF);\r |
63 | rotations[0] = top_bits;\r |
64 | \r |
65 | return store_count;\r |
66 | }\r |
67 | else\r |
68 | {\r |
69 | // There's nothing to wrap over to in the beginning\r |
70 | stores[store_count] = (imm >> left_shift) & 0xFF;\r |
71 | rotations[store_count] = (32 - left_shift) & 0x1F;\r |
72 | return store_count + 1;\r |
73 | }\r |
74 | break;\r |
75 | }\r |
76 | \r |
77 | stores[store_count] = (imm >> left_shift) & 0xFF;\r |
78 | rotations[store_count] = (32 - left_shift) & 0x1F;\r |
79 | \r |
80 | store_count++;\r |
81 | left_shift += 8;\r |
82 | }\r |
83 | }\r |
84 | \r |
85 | #define ror(value, shift) \\r |
86 | ((value) >> shift) | ((value) << (32 - shift)) \\r |
87 | \r |
88 | u32 arm_assemble_imm_32bit(u32 *stores, u32 *rotations, u32 store_count)\r |
89 | {\r |
90 | u32 n = ror(stores[0], rotations[0]);\r |
91 | u32 i;\r |
92 | printf("%x : %x\n", stores[0], rotations[0]);\r |
93 | \r |
94 | for(i = 1; i < store_count; i++)\r |
95 | {\r |
96 | printf("%x : %x\n", stores[i], rotations[i]);\r |
97 | n |= ror(stores[i], rotations[i]);\r |
98 | }\r |
99 | \r |
100 | return n;\r |
101 | }\r |
102 | \r |
103 | \r |
104 | int main(int argc, char *argv[])\r |
105 | {\r |
106 | u32 n = 0;\r |
107 | u32 stores[4];\r |
108 | u32 rotations[4];\r |
109 | u32 store_count;\r |
110 | u32 n2;\r |
111 | \r |
112 | if(argc != 1)\r |
113 | {\r |
114 | n = strtoul(argv[1], NULL, 16);\r |
115 | store_count = arm_disect_imm_32bit(n, stores, rotations);\r |
116 | n2 = arm_assemble_imm_32bit(stores, rotations, store_count);\r |
117 | printf("%08x -> %08x (%d stores)\n", n, n2, store_count);\r |
118 | return 0;\r |
119 | }\r |
120 | \r |
121 | do\r |
122 | {\r |
123 | store_count = arm_disect_imm_32bit(n, stores, rotations);\r |
124 | n2 = arm_assemble_imm_32bit(stores, rotations, store_count);\r |
125 | if(n != n2)\r |
126 | {\r |
127 | printf("Failure: %08x -/-> %08x\n", n, n2);\r |
128 | return -1;\r |
129 | }\r |
130 | n++;\r |
131 | } while(n != 0);\r |
132 | \r |
133 | printf("Done!\n");\r |
134 | return 0;\r |
135 | }\r |