.text
    .global classify
classify:
    ldr r1, [r0]
    ldr r2, [r0, #4]

    push {r4-r7}

    mov r4, #1
    lsl r4, r4, #31 // s
    and r4, r4, r2
    lsr r4, r4, #31

    ldr r5, =2047
    lsl r5, r5, #20
    and r5, r5, r2 // e
    lsr r5, r5, #20

    ldr r7, =1048575
    and r6, r2, r7
    cmp r1, #0
    movne r6, #1 // m

    cmp r4, #0
    bne signed_classify
unsigned_classify:
    cmp r5, #0
    bne unsigned_else

    cmp r6, #0
    moveq r0, #0 // PlusZero
    movne r0, #32 // PlusDenormal

    b exit_classify
unsigned_else:
    ldr r7, =2047
    cmp r5, r7

    movne r0, #16 // PlusRegular
    bne exit_classify

    cmp r6, #0
    moveq r0, #240 // PlusInf
    movne r0, #48 // SignalingNaN

    b exit_classify
signed_classify:
    cmp r5, #0
    bne signed_else

    cmp r6, #0
    moveq r0, #1 // MinusZero
    movne r0, #33 // MinusDenormal

    b exit_classify
signed_else:
    ldr r7, =2047
    cmp r5, r7

    movne r0, #17 // MinusRegular
    bne exit_classify

    cmp r6, #0
    moveq r0, #241 // MinusInf
    movne r0, #49 // QuietNaN

    b exit_classify
exit_classify:
    pop {r4-r7}
    bx lr