Re: [Tinycc-devel] Questions about commit 5b28165: Fix test 131 for 32 bits targets

[Ziyao]

On 2023-07-08 01:25, grischka wrote:
> Hi,
>
> well, problem is simply that with 32-bit longs your data
>    0x1234567890abcd
> would be truncated to
>    0x7890abcd
> and the output from %lx would not match the .expect file.

Thanks for explanation. But replacing 0x1234567890abcd with
0x12345678 (32-bit length) may be better?

> Btw is your fix incorrect.  The code that you "fixed" is about
> alignment but there was no alignment problem in your case.
>
> The real problem is below at "vtop->c.i += regsize;" which can
> advance the location to load the 2nd register only for local or
> global/static memory.

If the struct is not aligned, it will be copied to an aligned
address on stack. With this fix, returned structs without
VT_LVAL | VT_LLOCAL will also be copied onto stack as the same way
in which unaligned ones are copied, thus code below could handle it.

> For pointers it would need to emit an 'add r, regsize' instruction
> You can see such code in gv():
>
>     gaddrof();
>     vpushs(PTR_SIZE);
>     gen_op('+');
>     vtop->r |= VT_LVAL;
>
> -- gr
>
>
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--
Ziyao