Indirection vs. in-place update of closures

Simon Marlow simonmarhaskell at
Fri Jun 8 04:45:18 EDT 2007

Stefan Holdermans wrote:

> Is there any data available on how often, in GHC-generated code, 
> closures are being updated in-place as opposed to and in comparison with 
> being replaced by indirections to their results?
> How is it decided whether an in-place or an indirecting update is 
> performed?

The anser to these questions is easy.  Closures are never updated in place :-)

GHC used to have selective update-in-place in the past (pre-4.00), but it had 
highly complex interactions with various other aspects of the execution model, 
so we removed it, or rather, didn't re-implement it in the big runtime rewrite 
of 4.00.


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