From 1fb24fe85a19ae71b00875ff6c96ef1831dcf7e3 Mon Sep 17 00:00:00 2001 From: Arthur Eubanks Date: Wed, 6 Oct 2021 13:57:29 -0700 Subject: [PATCH] Reland [clang] Pass -clear-ast-before-backend in Clang::ConstructJob() This clears the memory used for the Clang AST before we run LLVM passes. https://llvm-compile-time-tracker.com/compare.php?from=d0a5f61c4f6fccec87fd5207e3fcd9502dd59854&to=b7437fee79e04464dd968e1a29185495f3590481&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. Turn this off for the interpreter since it does codegen multiple times. Relanding with fix for -print-stats: D111973 Differential Revision: https://reviews.llvm.org/D111270 --- clang/lib/Driver/ToolChains/Clang.cpp | 1 + clang/lib/Interpreter/Interpreter.cpp | 4 ++++ 2 files changed, 5 insertions(+) diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp index d2c08412d593..83afbc3952d8 100644 --- a/clang/lib/Driver/ToolChains/Clang.cpp +++ b/clang/lib/Driver/ToolChains/Clang.cpp @@ -4660,6 +4660,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA, // cleanup. if (!C.isForDiagnostics()) CmdArgs.push_back("-disable-free"); + CmdArgs.push_back("-clear-ast-before-backend"); #ifdef NDEBUG const bool IsAssertBuild = false; diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp index 02b3025297b6..d14940d2e132 100644 --- a/clang/lib/Interpreter/Interpreter.cpp +++ b/clang/lib/Interpreter/Interpreter.cpp @@ -113,6 +113,10 @@ CreateCI(const llvm::opt::ArgStringList &Argv) { Clang->getTarget().adjust(Clang->getDiagnostics(), Clang->getLangOpts()); + // Don't clear the AST before backend codegen since we do codegen multiple + // times, reusing the same AST. + Clang->getCodeGenOpts().ClearASTBeforeBackend = false; + return std::move(Clang); }