[PATCH] D80957: [LiveDebugValues] Cache LexicalScopes::getMachineBasicBlocks, NFCI

[Orlando Cazalet-Hyams via Phabricator via llvm-commits]

Orlando marked an inline comment as done.
Orlando added inline comments.


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Comment at: llvm/lib/CodeGen/LexicalScopes.cpp:328
+  return Set->count(MBB) != 0;
 }
 
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vsk wrote:
> Orlando wrote:
> > I'm not familiar with the extent of the usage of `LexicalScopes` throughout llvm, so I wonder if there's ever a case where we don't want the caching behaviour. i.e. is it conceivable that the result of `dominates` should change for the same inputs between calls?
> > 
> > Given this unfamiliarity I probably shouldn't be the one to give the final LGTM on this.
> LexicalScopes is used by LiveDebugValues and the debug info generators (it's referenced by DebugHandlerBase). A LexicalScopes instance can't be used to describe a changing MachineFunction, so the result of `dominates` can't change for the same inputs between calls. Also, the `dominates` method is currently only used by LiveDebugValues, where the caching seems to be useful.
That makes sense, thanks!


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https://reviews.llvm.org/D80957