[PATCH] D77952: [TLI] Reduce copies for TLI and TLA

[Teresa Johnson via Phabricator via cfe-commits]

tejohnson added inline comments.


================
Comment at: clang/lib/CodeGen/BackendUtil.cpp:689
   // Set up the per-function pass manager.
-  FPM.add(new TargetLibraryInfoWrapperPass(*TLII));
+  FPM.add(new TargetLibraryInfoWrapperPass(TargetTriple));
   if (CodeGenOpts.VerifyModule)
----------------
wenlei wrote:
> tejohnson wrote:
> > These changes mean we now construct a new TLII multiple times (e.g. both when we add the TargetLibraryInfoWrapperPass to the MPM earlier and to the FPM here, rather that just copying. Is this actually faster? It seems like it would be slower overall.
> Oops, this one isn't intentional... changed it back. Though for other instances where TLII isn't reused, similar change turns extra copy into move.
I suppose you could std::move the TLII here to avoid this second copy.

Do you know how much difference this patch makes on the compile time instruction count regressions seen with the original patch? It seems like it shouldn't be huge given that this is just during the pipeline setup for the module. But if it does explain the instruction count increases that's probably why it didn't regress the actual wall time measurements.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D77952/new/

https://reviews.llvm.org/D77952