[LLVMdev] AliasAnalysis update interface - a tale of sorrow and woe

[Pete Cooper]

> On Jul 2, 2015, at 1:17 PM, Hal Finkel <hfinkel at anl.gov> wrote:
> 
> I should add that I'm somewhat afraid, however, of the compile-time implications of adding the necessary hook.
I was just going to say this myself.

In fact, even if you don’t add a hook for tracking new values, just using value handles in AA could prove to be expensive.  

A typical optimized piece of code has more load instructions than binary instructions.  If you only cached loads with value handles, you’re already creating a huge number of handles, and these are currently entries in a map (pImpl->ValueHandles[V] if you’re curious).

TL;DR: If we are going to create this many value handles, we should strongly consider finding a way to represent them more cheaply.

Cheers,
Pete

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