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.syntax unified
.cpu cortex-m0plus
.thumb
.type statement, %function
.global statement
// R4 input buffer
// R2 output buffer
statement:PUSH {LR}
MOVS R3, R2 // save output buffer
BL whitespace // skip leading whitespace
BL label
CMP R0, 3 // only exit for code 3 (no colon at end of label)
BEQ exit
MOVS R1, R0
1: BL whitespace
MOVS R2, 0 // reset output buffer
STRB R2, [R3]
MOVS R2, R3
BL opcode // TODO opcodes longer than 4
ADD R0, R1
BNE exit
2: MOVS R0, R3
PUSH {R3}
BL putstrln
POP {R3}
LDR R0, [R3]
BL lookup
BNE exit
BL whitespace // TODO new return code for expected whitespace
BNE exit
ADR R0, parsers
LSLS R2, 2 // multiply by 4 to get byte offset
LDR R2, [R0, R2] // get address of parser
BLX R2
BNE exit
BL whitespace
LDRB R0, [R4] // get a byte from the input stream
TST R0, R0 // check if zero
BEQ exit // if it's zero then success
MOVS R0, 0x0B // return code 0B (extra input at end)
exit: POP {PC}
.align 4
parsers: .word regreg
.word regregimm
.word regimm
.word regregreg
.word imm
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