On 09/22/11 16:40, Alan Modra wrote:
> The bootstrap breakage happens on libmudflap/mf-hooks1.c, compiling
> __wrap_malloc. Eliding some detail, this function starts off as
>
> void *__wrap_malloc (size_t c)
> {
> if (__mf_starting_p)
> return __real_malloc (c);
>
> The "if" is bb2, the sibling call bb3, and shrink wrap rather nicely
> puts the prologue for the rest of the function in bb4. A great
> example of shrink wrap doing as it should, if you ignore the fact that
> optimizing for startup isn't so clever. However, bb-reorder inverts
> the "if" and moves the sibling call past other blocks in the function.
> That's wrong, because the dwarf unwind info for the prologue is not
> applicable for the sibling call block: The prologue hasn't been
> executed for that block. (The unwinder sequentially executes all
> unwind opcodes from the start of the function to find the unwind state
> at any instruction address.) Exactly the same sort of problem is
> generated by your "unconverted_simple_returns" code.
dwarf2cfi should be able to figure this out. I'd need to see RTL dumps
to get an idea what's going on.
Bernd
