A small ARM assembler

I made a small ARM assembler in Dart!

It just takes a string, like mov r0, #69 and emits the equivalent machine code: e3a00045. Initial tests with dissasemblers show it works pretty well though this isn't a full assembler, you can't do linking, macros, labels or even psudo-ops like push. It also has very little safeguards for incorrect flags on some instructions for example a pre-indexed ldrt.

Example output:

e3a00045 mov r0, #69
e12fff1e bx lr
09bc3ffc ldmedeq ip!, {a3-sp}
87e5d1ce strbhi r13, [v2, lr, asr #3]!
96992a4d ldrls a3, [sb], sp, asr #0x14

Live demo: https://dartpad.dartlang.org/9a4bb914d3d0d640061564517cf2e1ac

The following instructions are fully supported:

Data processing:
    AND{S}, EOR{S}, SUB{S}, RSB{S}
    ADD{S}, ADC{S}, SBC{S}, SRC{S}
    TST{S}, TEQ{S}, CMP{S}, CMN{S}
    ORR{S}, MOV{S}, BIC{S}, MVN{S}
Multiply:
    MUL{S}, MLA{S}
    UMULL{S}, UMLAL{S}, SMULL{S}, SMLAL{S}
Branching:
    BX, BL, B
Load/Store:
    STR{B}{T}, LDR{B}{T}
    LDM{FD|ED|FA|EA|IA|IB|DA|DB}
    STM{FD|ED|FA|EA|IA|IB|DA|DB}
    SWP{B}
Syscall:
    SWI, SVC
Condition codes:
    EQ, NE, CS, CC
    MI, PL, VS, VC,
    HI, LS, GE, LT
    GT, LE, AL