Re: [Valgrind-developers] allowing skins to instrument conditional jumps

[Nicholas N. <nj...@ca...>]

On 2 Oct 2002, Jeremy Fitzhardinge wrote:

> At present I'm using a single global, which means that I'll be creating
> spurious edges when there's context switches between threads.  The
> obvious place to store the information is in the baseBlock, and have it
> copied to/from the thread state on context switch.  I didn't see a
> mechanism for allocating variable space in the baseBlock, nor a way of
> conveniently addressing baseBlock offsets directly.  Should I add it?
> Or some other way of storing per-thread information?

Cachegrind stores variable-sized basic-block information.  It is pretty
low-level and dirty:  it allocates a flat array in which cost centres of
different sizes are all packed in together, with different cost centre
types distinguished by a tag.  The basic blocks' arrays are stored in a
hash table.

Josef's patch uses the same basic mechanisms, but does more complicated
stuff with the hash tables.

So there's not really any built-in mechanism, but you can certainly
allocate yourself some space for each basic block in SK_(instrument).  As
for addressing baseBlock offsets directly, I'm not sure what you mean --
the orig_addr is passed in to SK_(instrument);  is that not enough?  I'm
also not sure how threads ("per-thread information") relate to this.

N