Permalink
Cannot retrieve contributors at this time
Join GitHub today
GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.
Sign up
Fetching contributors…
Cannot retrieve contributors at this time
| // for more details see | |
| // https://dhconnelly.com/advent-of-code-2019-commentary.html#intcode-reverse-engineering | |
| // set the stack pointer to after the program data | |
| [ 0] adjrel imm(424) | |
| // call procedure C with ret=11 and arg0=X | |
| // halt if X < 0 | |
| [ 2] read rel(1) | |
| [ 4] mul imm(11) imm(1) rel(0) | |
| [ 8] jmpnot imm(0) imm(282) | |
| // call procedure B with ret=18 and arg0=X | |
| // 221 <- abs(X) | |
| [ 11] add imm(18) imm(0) rel(0) | |
| [ 15] jmpnot imm(0) imm(259) | |
| [ 18] add imm(0) rel(1) pos(221) | |
| // call procedure C with ret=31 and arg0=Y | |
| // halt if Y < 0 | |
| [ 22] read rel(1) | |
| [ 24] mul imm(31) imm(1) rel(0) | |
| [ 28] jmpnot imm(0) imm(282) | |
| // call procedure B with ret=38 and arg0=Y | |
| // Y = abs(Y) | |
| [ 31] mul imm(1) imm(38) rel(0) | |
| [ 35] jmpif imm(1) imm(259) | |
| // call procedure D with ret=57 and arg0=1, arg1=1, arg2=abs(Y) | |
| // because pos(23) = 1 | |
| // = Y | |
| // 222 <- Y | |
| [ 38] mul imm(1) pos(23) rel(2) | |
| [ 42] add imm(0) rel(1) rel(3) | |
| [ 46] add imm(0) imm(1) rel(1) | |
| [ 50] add imm(0) imm(57) rel(0) | |
| [ 54] jmpnot imm(0) imm(303) | |
| [ 57] mul rel(1) imm(1) pos(222) | |
| // call procedure A with ret=80 and arg0=259, arg1=X, arg2=X, arg3=X | |
| // = 259(X, X, X) = abs(X) | |
| [ 61] add pos(221) imm(0) rel(3) | |
| [ 65] mul imm(1) pos(221) rel(2) | |
| [ 69] mul imm(259) imm(1) rel(1) | |
| [ 73] add imm(80) imm(0) rel(0) | |
| [ 77] jmpif imm(1) imm(225) | |
| // call procedure D with ret=91 and arg0=X, arg1=149, arg2=X | |
| // = 149x^2 | |
| // -> 223 | |
| [ 80] mul imm(1) imm(149) rel(2) | |
| [ 84] add imm(0) imm(91) rel(0) | |
| [ 88] jmpif imm(1) imm(303) | |
| [ 91] mul rel(1) imm(1) pos(223) | |
| // call procedure A | |
| // with ret=118, arg0=225, arg1=225, arg2=259, arg3=^ | |
| // call A(A, A, B, Y) | |
| // = A(A, B, Y) | |
| // = A(B, Y) | |
| // = B(Y) | |
| // = abs(Y) | |
| [ 95] mul pos(222) imm(1) rel(4) | |
| [ 99] mul imm(259) imm(1) rel(3) | |
| [ 103] mul imm(225) imm(1) rel(2) | |
| [ 107] mul imm(225) imm(1) rel(1) | |
| [ 111] add imm(118) imm(0) rel(0) | |
| [ 115] jmpif imm(1) imm(225) | |
| // call D with ret=133 and Y, 127, Y | |
| // = 127y^2 | |
| [ 118] mul imm(1) pos(222) rel(3) | |
| [ 122] add imm(0) imm(127) rel(2) | |
| [ 126] mul imm(133) imm(1) rel(0) | |
| [ 130] jmpif imm(1) imm(303) | |
| // x0 = -above = -127y^2 | |
| // += 149x^2 | |
| // 223 <- 149x^2 - 127y^2 | |
| [ 133] mul rel(1) imm(-1) rel(1) | |
| [ 137] add pos(223) rel(1) rel(1) | |
| [ 141] mul imm(1) imm(148) rel(0) | |
| [ 145] jmpnot imm(0) imm(259) | |
| [ 148] add rel(1) imm(0) pos(223) | |
| // call A with ret=195 and arg0=303, arg1=14, arg2=Y, arg3=X | |
| // = D(14, Y, X) | |
| // rel(4) = X | |
| // = 14yx | |
| [ 152] add pos(221) imm(0) rel(4) | |
| // rel(3) = Y | |
| [ 156] mul pos(222) imm(1) rel(3) | |
| // rel(2) = 14 | |
| [ 160] mul imm(14) imm(1) rel(2) | |
| // *224 <- *303-2 = 301 | |
| [ 164] add pos(132) imm(-2) pos(224) | |
| // *224 <- *224 * 2 = 602 | |
| [ 168] mul pos(224) imm(2) pos(224) | |
| // *224 <- *224 + 3 = 605 | |
| [ 172] add pos(224) imm(3) pos(224) | |
| // *132 <- *132 * -1 = -303 | |
| [ 176] mul pos(132) imm(-1) pos(132) | |
| // *224 <- *224 + *132 = 605 - 303 = 302 | |
| [ 180] add pos(224) pos(132) pos(224) | |
| // rel(1) = *224 + 1 = 303 | |
| [ 184] add pos(224) imm(1) rel(1) | |
| // rel(0) = 195 | |
| [ 188] add imm(195) imm(0) rel(0) | |
| [ 192] jmpnot imm(0) pos(108) | |
| // call D with ret=214 and arg0=1, arg1=(14yx < 149x^2-127y^2), arg2=-1 | |
| [ 195] lt rel(1) pos(223) rel(2) | |
| [ 199] mul imm(1) pos(23) rel(1) | |
| [ 203] add imm(0) imm(-1) rel(3) | |
| [ 207] mul imm(214) imm(1) rel(0) | |
| [ 211] jmpnot imm(0) imm(303) | |
| // maybe |149x^2-127y^2| < 14yx ? | |
| // print ret+1 | |
| [ 214] add imm(1) rel(1) rel(1) | |
| [ 218] print rel(1) | |
| [ 220] halt | |
| // data section for the above | |
| [ 221] [0] // X | |
| [ 222] [0] // Y | |
| [ 223] [0] // 149x^2 if x < 149 then 149x^2 - 127y^2 | |
| [ 224] [0] // 127y^2 if y < 127 then scratch | |
| // calling convention for procedure with N parameters: | |
| // push ret and arguments 1..N onto the stack, in that order. | |
| // retrieve return value from rel+1 | |
| // procedure will move stack pointer forward by N+K, where | |
| // K is the number of locals to be used, then pop the stack | |
| // by moving it back by N+K and jump to rel(=ret). the return | |
| // value will be at rel+1. | |
| // ========================================================== | |
| // procedure A (4 params): | |
| // pos(249) <- arg0 | |
| // push arg1 | |
| // push arg2 | |
| // push arg3 | |
| // call procedure arg0 with ret=250, arg1, arg2, arg3 | |
| // return the return value | |
| // => | |
| // return arg0(arg1, arg2, arg3) | |
| [ 225] adjrel imm(5) | |
| [ 227] mul rel(-4) imm(1) pos(249) | |
| [ 231] mul imm(1) rel(-3) rel(1) | |
| [ 235] add rel(-2) imm(0) rel(2) | |
| [ 239] add rel(-1) imm(0) rel(3) | |
| [ 243] mul imm(1) imm(250) rel(0) | |
| [ 247] jmpif imm(1) imm(225) // 225 -> arg0, see above | |
| [ 250] mul imm(1) rel(1) rel(-4) | |
| [ 254] adjrel imm(-5) | |
| [ 256] jmpnot imm(0) rel(0) | |
| // ========================================================== | |
| // procedure B (1 params, 1 local): | |
| // x0 = 2 * (arg0 > 0 ? 1 : 0) - 1 | |
| // return x0 * arg0 | |
| // => | |
| // return abs(arg0) | |
| [ 259] adjrel imm(3) | |
| [ 261] lt imm(0) rel(-2) rel(-1) | |
| [ 265] mul rel(-1) imm(2) rel(-1) | |
| [ 269] add rel(-1) imm(-1) rel(-1) | |
| [ 273] mul rel(-1) rel(-2) rel(-2) | |
| [ 277] adjrel imm(-3) | |
| [ 279] jmpif imm(1) rel(0) | |
| // ========================================================== | |
| // procedure C: | |
| // x0 = arg0 < 0 | |
| // if !x0: goto 294 | |
| // print(0) | |
| // halt | |
| // 294: arg0 *= 1 | |
| // return | |
| // => | |
| // if x0 < 0: | |
| // print(0) | |
| // halt | |
| // return x0 | |
| [ 282] adjrel imm(3) | |
| [ 284] lt rel(-2) imm(0) rel(-1) | |
| [ 288] jmpnot rel(-1) imm(294) | |
| [ 291] print imm(0) | |
| [ 293] halt | |
| [ 294] mul rel(-2) imm(1) rel(-2) | |
| [ 298] adjrel imm(-3) | |
| [ 300] jmpnot imm(0) rel(0) | |
| // procedure D (3 params, 1 local): | |
| // arg0, arg1, arg2: | |
| // if | |
| // if arg1 >= arg0: | |
| // goto 346 | |
| [ 303] adjrel imm(5) | |
| [ 305] lt rel(-3) rel(-4) rel(-1) | |
| [ 309] jmpnot rel(-1) imm(346) | |
| // if arg0 > arg1: | |
| [ 312] add rel(-4) rel(-3) rel(-4) | |
| [ 316] mul rel(-3) imm(-1) rel(-1) | |
| [ 320] add rel(-4) rel(-1) rel(2) | |
| [ 324] mul rel(2) imm(-1) rel(-1) | |
| [ 328] add rel(-4) rel(-1) rel(1) | |
| [ 332] add imm(0) rel(-2) rel(3) | |
| [ 336] add imm(343) imm(0) rel(0) | |
| [ 340] jmpnot imm(0) imm(303) | |
| [ 343] jmpnot imm(0) imm(415) | |
| // if arg0 <= arg1 | |
| // x0 = arg2 < arg1 | |
| // if !x0: goto 387 | |
| // => if arg1 <= arg2: goto 387 | |
| [ 346] lt rel(-2) rel(-3) rel(-1) | |
| [ 350] jmpnot rel(-1) imm(387) | |
| // if arg2 < arg1: | |
| // arg1 += arg2 (from 88: 199) | |
| [ 353] add rel(-3) rel(-2) rel(-3) | |
| // local0 = -arg2 | |
| [ 357] mul rel(-2) imm(-1) rel(-1) | |
| // call proc D with arg0, arg2, arg1 | |
| // third arg: arg1 + local0 = arg1+arg2-arg2 = arg1 | |
| [ 361] add rel(-3) rel(-1) rel(3) | |
| // local0 = third arg * -1 = -arg1 | |
| [ 365] mul rel(3) imm(-1) rel(-1) | |
| // second arg: arg1 + local0 = arg1+arg2 - arg1 = arg2 | |
| [ 369] add rel(-3) rel(-1) rel(2) | |
| // first arg: arg0 | |
| [ 373] add imm(0) rel(-4) rel(1) | |
| // set ret=384 | |
| [ 377] mul imm(1) imm(384) rel(0) | |
| [ 381] jmpnot imm(0) imm(303) | |
| // jump to 415 (return) | |
| [ 384] jmpif imm(1) imm(415) | |
| // if arg1 <= arg2: | |
| // arg0 *= -1 (from 27: -1) (from 88: -50) | |
| [ 387] mul rel(-4) imm(-1) rel(-4) | |
| // arg0 += arg1 (from 27: 0) (from 88: 0) | |
| [ 391] add rel(-4) rel(-3) rel(-4) | |
| // arg2 *= arg1 (from 27: Y) (from 88: x * 149 = 7450) | |
| [ 395] mul rel(-3) rel(-2) rel(-2) | |
| // arg0 *= arg2 (from 27: 0) (from 88: 0) | |
| [ 399] mul rel(-2) rel(-4) rel(-4) | |
| // arg1 *= arg2 (from 27: Y) (from 88: x * x * 149 = 149x^2) | |
| [ 403] mul rel(-3) rel(-2) rel(-3) | |
| // arg2 = -arg0 (from 27: 0) (from 88: 0) | |
| [ 407] mul rel(-4) imm(-1) rel(-2) | |
| // x0 = arg1 + arg2 (from 27: Y) (from 88: 149x^2) | |
| [ 411] add rel(-3) rel(-2) rel(1) | |
| // return x0 = arg1 + arg2 (from 27: Y) (from 88: 149x^2) | |
| [ 415] mul imm(1) rel(1) rel(-4) | |
| [ 419] adjrel imm(-5) | |
| [ 421] jmpnot imm(0) rel(0) |