[PATCH] D111270: [clang] Pass -clear-ast-before-backend in Clang::ConstructJob()

[Arthur Eubanks via Phabricator via cfe-commits]

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aeubanks updated this revision to Diff 378327.
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aeubanks retitled this revision from "[clang] Always pass -clear-ast-before-backend" to "[clang] Pass -clear-ast-before-backend".
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aeubanks retitled this revision from "[clang] Pass -clear-ast-before-backend" to "[clang] Pass -clear-ast-before-backend in Clang::ConstructJob()".
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update


This clears the memory used for the Clang AST before we run LLVM passes.

https://llvm-compile-time-tracker.com/compare.php?from=b6a8c695542b2987eb9a203d5663a0740cb4725f&to=05aa5c451dd87b6a8d6c2410eaccb25edf15a16f&stat=max-rss
shows significant memory savings with no slowdown (in fact -O0 slightly speeds up).

For more background, see
https://lists.llvm.org/pipermail/cfe-dev/2021-September/068930.html.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D111270

Files:
  clang/lib/Driver/ToolChains/Clang.cpp


Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -4661,6 +4661,7 @@
   // cleanup.
   if (!C.isForDiagnostics())
     CmdArgs.push_back("-disable-free");
+  CmdArgs.push_back("-clear-ast-before-backend");
 
 #ifdef NDEBUG
   const bool IsAssertBuild = false;


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