diff options
Diffstat (limited to 'assembler/assemble.s')
| -rw-r--r-- | assembler/assemble.s | 147 |
1 files changed, 88 insertions, 59 deletions
diff --git a/assembler/assemble.s b/assembler/assemble.s index bf31edf..ef3893d 100644 --- a/assembler/assemble.s +++ b/assembler/assemble.s @@ -1,71 +1,100 @@ +.syntax unified +.cpu cortex-m0plus +.thumb + +.type assemble, %function +.global assemble + +// TODO: +// - implement opcode parser +// - test each instruction (do this later -- much easier) +// - test 4-bit reg instructions +// - test BEQ overlaps +// - decide on additional push or pops + assemble: - BL receive_op - LDR R5, =0x20002000 // opcode table - LDR R1, =0x20001000 // opcode buffer base addr -loop: - LDR R0, [R5, 0] // load the string addr - BL string_compare - BEQ match - ADDS R5, 8 // next row of table - LDR R0, =0x20002080 // opcode table end - CMP R5, R0 - BLO loop // Keep going if lower than end - B redo_line // redo line if opcode was not found -match: - LDR R6, [R5, 4] // load the parse instructions + // LDR R3, [SP, 20] + MOVS R6, 0 + LDR R7, =0x00C8E893 + // LDR R7, =0xE0E3A588 + MOVS R0, ' + MOV R8, R0 main_loop: - MOVS R0, 0xFF // lsb mask - ANDS R0, R6 // store in R0 - MOVS R1, 0x80 // bit 7 mask - TST R0, R1 // compare (AND) to R0 byte - BNE handle_imm // if IMM (== 1) - LSRS R0, 4 // R0 hold 3 or 4 (or 0) - BEQ handle_brackets // if BRACKETS (== 0) -handle_reg: - BL register // result is put in R4 - MOVS R0, 0x0F // lower nibble mask - ANDS R0, R6 // store shift amount in R0 - LSLS R4, R0 // shift the result by the shift amount - ORRS R5, R4 // OR the register code into the word under construction + LSRS R0, R7, 8 // just peek + BNE skip // if more stuff then skip + MOVS R0, '\r + MOV R8, R0 //set end char to carriage return +skip: + // MOVS R0, 0xFF // lsb mask + // ANDS R0, R7 // store in R0 + UXTB R0, R7 // store lsb in R0 + LSRS R1, R0, 4 // upper nibble + CMP R1, 0xC // if 0xxxxxxx or 10xxxxxx + BLO opcode + CMP R1, 0xE // if 110xyyyy + BLO handle_imm +handle_reg: // if 111xyyyy + MOVS R1, (1<<4) // bit 4 mask + ANDS R0, R1 // get bit 4 + ADDS R0, 3 // add 3 to it (now 3 or 4) + BL register // result is put in R4 + MOVS R0, 0x0F // lower nibble mask + ANDS R0, R7 // store shift amount in R0 + LSLS R4, R0 // shift the result by the shift amount + ORRS R6, R4 // OR the register code into the word under construction B done_stuff +opcode: + MOVS R2, 9 // shift amount for 7-bit opcode + MOVS R1, (1<<7) // bit 7 mask + TST R0, R1 // check bit 7 + BEQ fin // if zero done + BICS R0, R1 // clear bit 7 + MOVS R2, 11 // shift amount for 5-bit opcode high + MOVS R1, (1<<5) // bit 5 mask + TST R0, R1 // check bit 5 + BEQ fin // if zero done + BICS R0, R1 // clear bit 5 + MOVS R2, 6 // shift amount for 5-bit opcode low +fin: + LSLS R0, R2 + ORRS R6, R0 + B here handle_imm: MOVS R1, 0x0F // lower nibble mask ANDS R0, R1 // store immediate width in R0 BL octal // result is put in R4 - MOVS R0, 0x7F // least significant 7 bits mask - ANDS R0, R6 // store ls 7 bits in R0 - LSRS R0, 4 // shift right to get shift amount + LSLS R0, R7, 27 + LSRS R0, 31 + MOVS R2, 6 + MULS R0, R2 // R0 has shift amount (0 or 6) LSLS R4, R0 // shift the result by the shift amount + ORRS R6, R4 // OR the immediate into the word under construction done_stuff: - LSRS R6, 0x8 // get next parse instruction - BEQ done // if it's zero there are no more things to parse - MOVS R0, 0 // copy the end_char into R0 - ORRS R0, R9 - BL uart_send // echo the comma (or bracket) -10: - BL get_char - MOVS R1, ' // space char - CMP R0, R1 - BNE 10b // keep trying if not space - BL uart_send // echo the space - B main_loop -handle_brackets: - BL get_char // char in R0 - MOVS R1, '[ // open bracket - CMP R0, R1 - BNE handle_brackets // keep trying if not bracket - BL uart_send // echo bracket - MOVS R8, 1 // 1 means we are now in brackets - LSRS R6, 0x8 // get next parse instruction - BNE main_loop + MOV R0, R8 // copy the end_char into R0 + BL uart_send // echo the space (or carriage return) +here: + LSRS R7, 0x8 // get next parse instruction + BNE main_loop // if it's nonzero there are more things to parse done: - TST R8, R8 // R8 == whether we are in bracket or not - BEQ no_brackets - MOVS R0, '] // echo bracket - BL uart_send -no_bracket: - MOVS R0, '\r // send carriage return - BL uart_send MOVS R0, '\n // send newline BL uart_send - B next_instr + MOVS R0, R6 + BL send_hex + B assemble + +.type get_char, %function +.global get_char + +// R8: end_char +get_char: + PUSH {LR} + BL uart_recv + CMP R0, 025 // ^U (NAK) + BEQ redo_line + // CMP R0, 004 // ^D (EOT) + // BEQ done_for_real + CMP R0, R8 + POP {PC} +redo_line: + POP {R0} + B done |