Code which demonstrates strangely aligned stack arguments in ARM64.

main.s

_main:
    // Prologue
    stp     x29, x30, [sp, #-16]!
    mov     x29, sp
    
    sub     sp, sp, #96         // Space for stack paramters to +[Foo method::::::::]
    
    // First two implicit arguments to any Objc method call
    ldr     x0, #552            // Objc class ref: Foo
    ldr     x1, #536            // Objc selector ref: "method::::::::"
    
    // Same `Bar` struct used for all `Bar` args
    movz    w8, #0xbe
    movz    w9, #0xbf
    movz    w10, #0xaf
    
    
    stp     x8, x9, [x29, #-24] // Arg `f` storage (@ `[sp, #72]`)
    stur    x10, [x29, #-8]
    
    stp     x8, x9, [sp, #48]   // Arg `c` storage (@ `[sp, #48]`)
    str     x10, [sp, #64]
    
    stp     x8, x9, [sp, #24]   // Arg `a` storage (@ `[sp, #24]`)
    str     x10, [sp, #40]
    
    
    orr     w8, wzr, #0x2       // Arg `h` (@ `[sp, #8]`)
    str     x8, [sp, #8]
    
    orr     w8, wzr, #0x1       // Arg `g` (@ `[sp]`)
    str     x8, [sp]
    
    sub     x2, x29, #24        // Arg `a` ref
    movz    w3, #0x3            // Arg `b`
    add     x4, sp, #48         // Arg `c` ref
    movz    w5, #0x5            // Arg `d`
    movz    w6, #0x6            // Arg `e`
    add     x7, sp, #24         // Arg `f` ref
    
    // Method call
    bl      0x100007f24         // Objc message: +[Foo method::::::::]
    
    // Epilogue
    movz    w0, #0
    mov     sp, x29
    ldp     x29, x30, [sp], #16
    ret

Objc.m

typedef struct _Bar {
    long x;
    long y;
    long z;
} Bar;

@interface Foo : NSObject
+ (void)method:(Bar)a :(long)b :(Bar)c :(long)d :(long)e :(Bar)f :(long)g :(long)h;
    @end
@implementation Foo
+ (void)method:(Bar)a :(long)b :(Bar)c :(long)d :(long)e :(Bar)f :(long)g :(long)h {
    f.x = 0;
}
@end

int main() {
    Bar c;
    c.x = 0xbe;
    c.y = 0xbf;
    c.z = 0xaf;
    [Foo method:c:3:c:5:6:c:1:2];
}