diff options
Diffstat (limited to 'assembler/octal.s')
| -rw-r--r-- | assembler/octal.s | 116 |
1 files changed, 48 insertions, 68 deletions
diff --git a/assembler/octal.s b/assembler/octal.s index 18abebd..62e2b1e 100644 --- a/assembler/octal.s +++ b/assembler/octal.s @@ -5,71 +5,51 @@ .type octal, %function .global octal -octal: - PUSH {LR} - MOVS R5, R0 - - // Handle bit-width = 0 - BNE 30f -10: - BL get_char - CMP R0, '0 - BNE 10b - BL uart_send - MOVS R4, 0 -20: - BL get_char - BNE 20b - POP {PC} -30: - - // R4 will become '1 or '3 or '7 - MOVS R0, 3 - CMP R5, 3 - BHS 40f - MOVS R0, R5 -40: - MOVS R4, 1 - LSLS R4, R0 - ADDS R4, ('0 - 1) - - // Get first char -50: - BL get_char - CMP R0, '0 - BLO 50b - CMP R0, R4 - BHI 50b - BL uart_send - SUBS R0, '0 - MOVS R4, R0 - - // Subtract 1, 2, or 3 from bit-width - MOVS R1, 0 -60: - ADDS R1, 1 - LSRS R0, 1 - BNE 60b - SUBS R5, R1 - - // Loop for remaining chars -70: - CMP R5, 3 - BLO 80f - BL get_char - BEQ 90f - CMP R0, '0 - BLO 70b - CMP R0, '7 - BHI 70b - BL uart_send - SUBS R0, '0 - LSLS R4, 3 - ADDS R4, R0 - SUBS R5, 3 - B 70b -80: - BL get_char - BNE 80b -90: - POP {PC} +octal: PUSH {LR} // 0c0000 0xB500 ; SAVE LINK REGISTER + MOVS R5, R0 // 0x0002 0x0005 ; SAVE BIT WIDTH + BNE 30f // 0x0004 0xD1 ; SKIP IF BIT WIDTH != 0 +10: BLX R10 // 0x0006 0x ; GET CHAR + CMP R0, '0 // 0x000A 0x2830 ; COMPARE TO '0 CHAR + BNE 10b // 0x000C 0xD1 ; GET ANOTHER CHAR IF NOT '0 + BLX R9 // 0x000E 0x ; OTHERWISE ECHO '0 CHAR + MOVS R4, 0 // 0x0012 0x2400 ; SET RESULT TO 0 +20: BLX R10 // 0x0014 0x ; GET CHAR + BNE 20b // 0x0018 0xD1 ; LOOP IF NOT END CHAR + POP {PC} // 0x001A 0xBD00 ; RETURN IF END CHAR +30: MOVS R0, 3 // 0x001C 0x2003 ; DEFAULT TO 3 + CMP R5, 3 // 0x001E 0x2D03 ; CHECK BIT WIDTH + BHS 40f // 0x0020 0xD2 ; IF BIT WIDTH >= 3 KEEP R0 == 3 + MOVS R0, R5 // 0x0022 0x0028 ; IF BIT WIDTH < 3 COPY TO R0 +40: MOVS R4, 1 // 0x0024 0x2401 ; 2^0 + LSLS R4, R0 // 0x0026 0x4084 ; 2^(MAX(BIT WIDTH, 3)) + ADDS R4, ('0 - 1) // 0x0028 0x342F ; '1 OR '3 or '7 +50: BLX R10 // 0x002A 0x ; GET FIRST CHAR + CMP R0, '0 // 0x002E 0x2830 ; COMPARE WITH '0 + BLO 50b // 0x0030 0xD3 ; RETRY IF BELOW OCTAL RANGE + CMP R0, R4 // 0x0032 0x42A0 ; COMPARE WITH END CHAR + BHI 50b // 0x0034 0xD8 ; RETRY IF ABOVE RANGE + BLX R9 // 0x0036 0x ; ECHO IF IN RANGE + SUBS R0, '0 // 0x003A 0x3830 ; GET VALUE FROM CHAR + MOVS R4, R0 // 0x003C 0x0004 ; STORE VALUE IN RESULT + MOVS R1, 0 // 0x003E 0x2100 ; BIT WIDTH FOR FIRST CHAR +60: ADDS R1, 1 // 0x0040 0x3101 ; INCREMENT FIRST CHAR WIDTH + LSRS R0, 1 // 0x0042 0x0840 ; SHIFT RIGHT ONE BIT + BNE 60b // 0x0044 0x ; IF NONZERO STAY IN LOOP + SUBS R5, R1 // 0x0046 0x1A6D ; SUBTRACT FIRST CHAR WIDTH FROM TOTAL +70: CMP R5, 3 // 0x0048 0x2D03 ; COMPARE BIT WIDTH TO 3 + BLO 80f // 0x004A 0xD3 ; EXIT LOOP IF LESS THAN 3 + BLX R10 // 0x004C 0x ; GET ANOTHER CHAR + BEQ 90f // 0x0050 0xD0 ; IF END CHAR EXIT LOOP + CMP R0, '0 // 0x0052 0x2830 ; BOTTOM OF OCTAL RANGE + BLO 70b // 0x0054 0xD3 ; RETRY IF BELOW + CMP R0, '7 // 0x0056 0x2837 ; TOP OF OCTAL RANGE + BHI 70b // 0x0058 0xD8 ; RETRY IF ABOVE + BLX R9 // 0x005A 0x ; ECHO IF IN RANGE + SUBS R0, '0 // 0x005E 0x3830 ; GET VALUE FROM CHAR + LSLS R4, 3 // 0x0060 0x00E4 ; SHIFT OLD VALUE BY ONE DIGIT + ADDS R4, R0 // 0x0062 0x1824 ; ACCUMULATE INTO VALUE + SUBS R5, 3 // 0x0064 0x3D03 ; DECREMENT BIT WIDTH BY 3 + B 70b // 0x0066 0xD0 ; LOOP FOR ANOTHER DIGIT +80: BLX R10 // 0x0068 0x ; GET A CHAR + BNE 80b // 0x006C 0xD1 ; LOOP UNTIL END CHAR +90: POP {PC} // 0x006E 0xBD00 ; RETURN |