Help getting amd64 assembly patch into wine?

Joerg-Cyril.Hoehle at Joerg-Cyril.Hoehle at
Fri Oct 5 09:27:24 CDT 2012


I found your message very unclear.
>The patch adds support for OpenMP programs like this:
And then you start talking about vcomp_fork without telling us where
it comes from and what it should do.  So I'll guess from the names.
- vcomp_for_static/sections_init sound like startup code
  initialisation of BSS and DATA segments.
- fork sounds like running code with thread-local copies to BSS and DATA
  I guess vcomp eats up one register or parameter to keep a pointer to
  the thread-local storage.

>    p_vcomp_fork(0, 1, _test_vcomp_fork_worker1, &ncalls);
Your code does not explain what the first parameter is.

I believe that va_list etc. is not going to lead you anywhere.

First, va_* is only one side.
E.g. include/wine/test.h uses va_list and __builtin_ms_va_list

You need the other side too, namely, given a va_* structure, call a
function X with the parameters given in that structure.

The GNU ffcall library
distinguishes both.  One half is called vacall, the other one avcall :-)

Your tests show that you need 2 different va_lists:
>    p_vcomp_fork(0, 5, _test_vcomp_fork_worker5, 1, 2, 3, 4, 5);

1. On the receiver side, va_start would create a va_list for the parameter set
   (0, 5, function pointer, 1, 2, 3, 4, 5)

2. But now you need to call something with the apparent parameter set
   (1, 2, 3, 4, 5)
   (I say apparent because you don't explain the vcomp execution model.
    Is a hidden parameter added somewhere? What's that first parameter 0 to fork?)

Obviously, if you don't know the internals of a va_list, you'll not be
able to transform one structure into the other.

So bad, now what is actually needed?

Think assembly.

Using your test example:
+    p_vcomp_fork(0, 5, _test_worker5, 1, 2, 3, 4, 5);

_vcomp_fork finds data:
1. on the stack
2. in registers
3. in FP registers
The C stack layout is (topmost first):
  0, then 5, &_test_worker5, 1, 2, etc.

What you obviously need to do is, supposing the first parameters are
duplicated in registers:

- Save registers and possibly FP registers into a structure
- Remember the stack pointer and number of elements,
  -- hereby creating a va_args structure whose layout you know.
- CreateThread?? etc.
- Restore registers
- Shift register parameters by 3 items: (assuming 5 such registers)
  register-for-param-1 (1) <- register-for-param-4
  register-for-param-2 (2) <- register-for-param-5
- Copy from stack into registers
  register-for-param-3 (3) <- from stack
  register-for-param-4 (4) <- from stack
  register-for-param-5 (5) <- from stack
- POP 0 and 5
- POP &_test_worker5 into scratch register
- JMPTO _test_worker5 via scratch register

This assumes there's nothing like CreateThread so you can run from the original stack.
If there were, you'd need to copy the 5 elements from the stack to the new one
(which is presumably why vcomp_fork receives their number as parameter).

Does this help?
	Jörg Höhle

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