[PATCH] D140627: [orc] Pass big JITTargetMachineBuilder parameters by reference to avoid unnecessary copies

[Feng Zou via Phabricator via llvm-commits]

fzou1 added a comment.

In D140627#4075812 <https://reviews.llvm.org/D140627#4075812>, @lhames wrote:

> Hi @fzou1,
>
> JITTargetMachineBuilders are only moved around at startup at the moment, and they're only ~0.5kb. Have they been observed to have a performance impact? If so we should probably transfer them via `unique_ptr` to avoid the copies, but I'm not sure it's necessary yet.

Sorry. No performance impact observed. They're nice-to-have changes. If needed, I'll update the patch with `unique_ptr`.



================
Comment at: llvm/docs/tutorial/BuildingAJIT1.rst:195-197
+    auto EPC = SelfExecutorProcessControl::Create();
+    if (!EPC)
+      return EPC.takeError();
----------------
lhames wrote:
> The introduction of EPC here seems unrelated to the other changes?
Yes. But the example code is out of date and should be same as in KaleidoscopeJIT.h header file.


================
Comment at: llvm/docs/tutorial/BuildingAJIT2.rst:61
   private:
-    ExecutionSession ES;
-    RTDyldObjectLinkingLayer ObjectLayer;
-    IRCompileLayer CompileLayer;
-    IRTransformLayer TransformLayer;
+    std::unique_ptr<ExecutionSession> ES;
 
----------------
lhames wrote:
> Is this change related to the rest of the patch?
Partly yes. This example code is out of date. I updated it together with the code of passing argument by reference.


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