| 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 |