Hi,

I’ve been hacking minic to try and add return types and variadic 
arguments - https://github.com/DangerMouseB/minc. So far I quite
like it however I’m hitting some snags with QBE:

 
I’ve compiled this C program with clang:

char LF3() {return 10;}


And compiled this QBE IR program:


export function uh $LF() {
@start
    %t =w mul 12, 256
    %t =w add %t, 10
    call $printf(l $gLF, ..., w %t, w %t, ub 10)
    ret %t
}

export function w $LF2() {
@start
    %t =w add 10, 0
    ret %t
}

export function w $main(w %.0, l %.1) {
@start
    # uh version
    %pA =l call $LF()
    call $printf(l $gpA, ..., l %pA, l %pA, ub 10)
        %A =w loaduh %pA
    call $printf(l $gA, ..., w %A, w %A, ub 10)
    call $printf(l $gA, ..., uh %A, uh %A, ub 10)
    call $printf(l $gA, ..., ub %A, ub %A, ub 10)

    %B =w extub %A
    call $printf(l $gB, ..., w %B, w %B, ub 10)

    %C =w call $LF2()
    call $printf(l $gC, ..., ub %C, ub %C, ub 10)

    # C version
    %D =ub call $LF3()
    call $printf(l $gD, ..., ub %D, ub %D, ub 10)

    ret 0
}

data $gLF = { b "LF: 0x%.8x %d %c", b 0 }
data $gpA = { b "pA: 0x%.16x %llu %c", b 0 }
data $gA  = { b "A:  0x%.8x %d %c", b 0 }
data $gB  = { b "B:  0x%.8x %d %c", b 0 }
data $gC  = { b "C:  0x%.8x %d %c", b 0 }
data $gD  = { b "D:  0x%.8x %d %c", b 0 }


If I make LF’s signature to be:

export function ub $LF


QBE gives me:

arm64/emit.c: dying: invalid class

So I can only get LF to work if I return a uh AND I treat
the result as a pointer to a uh. When I call LF3 (the C function) I can
treat the return value as a char rather than a char*.

1) is the error with ub a bug or my mistake?
2) is there a way to return a char from a QBE function as opposed to a
   char*?


For reference current output is:

LF: 0x00000c0a 3082
pA: 0x00000000041e3fa8 4364058536
A:  0x00000c0a 3082
A:  0x00000c0a 3082
A:  0x0000000a 10
B:  0x0000000a 10
C:  0x0000000a 10
D:  0x0000000a 10


This is on macOS with an M1.


Thanks for your help.

-- David