Witch of Git - jade-rose/blob - isa.txt

   1 ROSE-8 v0.2
   2 ISA by Jordan Rose
   3
   4 Eight completely symmetric general-purpose registers (r0-7)
   5 Special registers: pc (16-bit address), it (accumulator), data1 (segment), data2 (segment), code (segment)
   6
   7 7654_3210
   8
   9 0000_0000          TRAP (invalid)
  10      0001          NOPE "no operation" (with a more fun mnemonic)
  11      0010          PRNT print it (for debugging or toy programs)
  12      0011
  13      010x
  14      0110          CABA call absolute code[it], it <- return addr, code <- return segment
  15      0111          COFA call offset pc ± it, it <- return offset (-it + 1)
  16
  17 0000_1ooo          ALU1 it <- {zero, lsl1, lsr1, asr1, incr, decr, comp, negt} it
  18
  19 0001_0000          GET1 it <- data1
  20      0001          GET2 it <- data2
  21      0010          GETC it <- code
  22      0011               (reserved for another special register)
  23      01xx
  24      1000          SET1 data1 <- it
  25      1001          SET2 data2 <- it
  26      1010          SETC code  <- it
  27      1011               (reserved for another special register)
  28      11xx
  29
  30 0010_0aaa          GETR it <- it
  31    0_1aaa          SETR ra <- it
  32    1_0aaa          SWAP ra <- it, it <- ra
  33    1_1aaa          ISLT "is less than", for testing overflow / carries: it <- (it < ra) ? 1 : 0
  34
  35 01oo_oaaa          ALUR it <- it {addr, subr, andr, iorr, xorr, lslr, lsrr, asrr} ra
  36
  37 100i_0aaa          LD1U it <- data1[ra], then ra += i
  38   0i_1aaa          ST1U data1[ra] <- it, then ra += i
  39   1i_0aaa          LD2U it <- data2[ra], then ra += i
  40   1i_1aaa          ST2U data2[ra] <- it, then ra += i
  41
  42 110x_xaaa               (reserved w/ register)
  43 1110_xaaa               (reserved w/ register)
  44
  45 1111_00oo iiiiiiii ALUI it <- it {andi, iori, xori, (see below)} i
  46      0011 0iiiiiii ADDI it <- it + i
  47      0011 10oooiii BITI it <- it {roli, lsli, lsri, asri, clri, insi, togi, exti} i
  48      0011 11iiiiii ADDI it <- it + (whole field, thus allowing many negative numbers)
  49      0100 iiiiiiii BEZI branch pc ± i if it == 0
  50      0101 iiiiiiii JOFI jump offset to pc ± i
  51      0110 iiiiiiii CABI call absolute code[i], it <- return addr, code <- return segment
  52      0111 iiiiiiii COFI call offset pc ± i, it <- return offset (-i + 2)
  53      10xx iiiiiiii      (reserved w/ immediate)
  54      110x iiiiiiii      (reserved w/ immediate)
  55      1110 iiiiiiii GETI it <- i
  56      1111 xxxxxxxx EXT1 extended encoding for "future-proofing"
  57
  58 11 free no-argument encodings
  59 6 free register encodings - possibly load-then-decrement? possibly 16-bit ADD and SUB with register pairs?
  60 6 free immediate encodings
  61
  62 Some dubiously "nice" properties:
  63 - 0 is invalid
  64 - 1111_xxxx takes immediate
  65 - Register instructions are all consecutive (0010_0aaa through 1110_1aaa)
  66 - No reg/imm ops, so data line can be the immediate
  67 - Two data segments, because I'm generous like that
  68 - get/set pairs consistently differentiated by bit 5
  69 - Future-proofing! Because that's definitely a thing that this set needs
  70 - The nicest instruction is "ADDR r5"
  71 - Near and far calls (okay, this is not nice)