[LLVMdev] Nested functions
Vikram S. Adve
vadve at cs.uiuc.edu
Mon Nov 22 10:03:55 PST 2004
On Nov 22, 2004, at 12:05 PM, Chris Lattner wrote:
> On Sun, 21 Nov 2004, Dirk Muysers wrote:
>> Was there already some reflection about how to lower the concept of
>> functions (and the corresponding static links) into llvm?
> This was discussed back in August, which discusses it, provides a
> and an example:
That's a rather simplistic example. I wouldn't recommend doing it this
way -- I see at least 2 problems with it:
(1) With recursion, the inlining being assumed here would not happen.
This means the struct initialization won't be optimized away so nicely
and it can get really expensive. Even without recursion, inlining
would be impractical if you have many nested procedures and deep
(2) If you don't rely on inlining, initializing the structs you have to
pass around will get horrendously expensive with large numbers of local
variables. (Note that without inlining, the structs will *not* be
scalar-replaced because they have to passed as arguments.)
There's a reason why code generators use static links.
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