[PATCH] D17792: Initialize much of AssemblyWriter lazily.

[Justin Lebar via llvm-commits]

jlebar added inline comments.

================
Comment at: lib/IR/AsmWriter.cpp:82
@@ +81,3 @@
+
+  std::function<T()> Initializer;
+  Optional<T> Obj;
----------------
timshen wrote:
> Man, by last time I looked at libstdc++, it's like 48 bytes on 64-bit machines...
> 
> Even if Lazy keeps track of the raw lambda, the lambda may still capture stuff and have memory footprint.
> 
> Now I think it's a bad idea. It's as bad as that dtor doesn't have parameters so each container, which may be in a parent container, needs to keep its allocator.
> 
> Sorry, I think the Optional version is better. :(
> 
> BTW, how hard is it to make the user side lazy, rather the library side?
> Man, by last time I looked at libstdc++, it's like 48 bytes on 64-bit machines...

Eh, I don't think this is a big deal, compared to all the other work we're doing here.  :)

> Even if Lazy keeps track of the raw lambda, the lambda may still capture stuff and have memory footprint.

Indeed, but these lambdas don't, so we're ok in that respect!

> It's as bad as that dtor doesn't have parameters so each container, which may be in a parent container, needs to keep its allocator.

:)  Here I'm much more concerned about readability.  Like, we're making this *way* faster in any case; the extra few bytes or whatever isn't a big deal.

> BTW, how hard is it to make the user side lazy, rather the library side?

I'm not sure what you mean; can you give me an example?


http://reviews.llvm.org/D17792