[PATCH] D121643: [llvm-profgen] On-demand pseudo probe decoding

[Lei Wang via Phabricator via llvm-commits]

wlei added inline comments.


================
Comment at: llvm/tools/llvm-profgen/ProfileGenerator.cpp:374
 
+void ProfileGeneratorBase::collectProfiledFunctions() {
+  std::unordered_set<const BinaryFunction *> ProfiledFunctions;
----------------
wlei wrote:
> For CS profile,  the input contains CallStack + LBRStack, but here it only considers the addresses from LBRStack(Range + Branch) to compute profiledFunctions. Does it miss some functions whose address(frame) is only from CallStack?
> 
> For example, if we only have one following entry:
> [main @ foo] : {rangeFrom : rangeTo}
>  
> Supposing rangeFrom and rangeTo only belong to `foo`(foo is not inlined to main), then the result of ProfiledFunctions only contains `foo` and misses `main`, right?
> 
> From the term "ProfiledFunctions", it should be `foo`, but for CS inlining, I guess we still need the frame `main`?
> 
Sorry, I missed your notes on the summary. 
> "Note that in on-demand mode, a calling context may be truncated at a caller which does not have sample. This is a discrepancy from the complete mode. However, with the CS preinliner such context will always be truncated from the compiler inlining point of view." 

So in on-demand mode, it will implicitly trim some contexts, even before CS-preinliner or cold-context-trimming. 


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  https://reviews.llvm.org/D121643/new/

https://reviews.llvm.org/D121643