aeubanks created this revision.
Herald added subscribers: dexonsmith, dang.
aeubanks requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
This is to save memory for Clang compiles.
Measuring building PassBuilder.cpp under /usr/bin/time, max rss goes from
0.93GB to 0.7GB.
This does not turn it by default yet.
I've turned on the option locally and run it over a good amount of files
without any issues.
For more background, see
https://lists.llvm.org/pipermail/cfe-dev/2021-September/068930.html.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D111105
Files:
clang/include/clang/Basic/CodeGenOptions.def
clang/include/clang/Driver/Options.td
clang/lib/CodeGen/CodeGenAction.cpp
clang/test/Misc/clear-ast-before-backend.c
Index: clang/test/Misc/clear-ast-before-backend.c
===================================================================
--- /dev/null
+++ clang/test/Misc/clear-ast-before-backend.c
@@ -0,0 +1,3 @@
+// RUN: %clang -target x86_64-linux-gnu -c -Xclang -clear-ast-before-backend
%s -S
+// RUN: %clang -target x86_64-linux-gnu -c -Xclang -clear-ast-before-backend
%s -S -### 2>&1 | FileCheck %s
+// CHECK: "-clear-ast-before-backend"
Index: clang/lib/CodeGen/CodeGenAction.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenAction.cpp
+++ clang/lib/CodeGen/CodeGenAction.cpp
@@ -351,6 +351,11 @@
}
}
+ // FIXME: Fix cleanup issues with clearing the AST when we properly free
+ // things.
+ if (CodeGenOpts.DisableFree && CodeGenOpts.ClearASTBeforeBackend)
+ C.getAllocator().Reset();
+
EmbedBitcode(getModule(), CodeGenOpts, llvm::MemoryBufferRef());
EmitBackendOutput(Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts,
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -5297,6 +5297,9 @@
def disable_free : Flag<["-"], "disable-free">,
HelpText<"Disable freeing of memory on exit">,
MarshallingInfoFlag<FrontendOpts<"DisableFree">>;
+def clear_ast_before_backend : Flag<["-"], "clear-ast-before-backend">,
+ HelpText<"Clear the Clang AST before running backend code generation">,
+ MarshallingInfoFlag<CodeGenOpts<"ClearASTBeforeBackend">>;
def enable_noundef_analysis : Flag<["-"], "enable-noundef-analysis">,
Group<f_Group>,
HelpText<"Enable analyzing function argument and return types for mandatory
definedness">,
MarshallingInfoFlag<CodeGenOpts<"EnableNoundefAttrs">>;
Index: clang/include/clang/Basic/CodeGenOptions.def
===================================================================
--- clang/include/clang/Basic/CodeGenOptions.def
+++ clang/include/clang/Basic/CodeGenOptions.def
@@ -54,6 +54,7 @@
CODEGENOPT(EnableAIXExtendedAltivecABI, 1, 0) ///< Set for -mabi=vec-extabi.
Enables the extended Altivec ABI on AIX.
ENUM_CODEGENOPT(FramePointer, FramePointerKind, 2, FramePointerKind::None) ///
frame-pointer: all,non-leaf,none
+CODEGENOPT(ClearASTBeforeBackend , 1, 0) ///< Free the AST before running
backend code generation. Only works with -disable-free.
CODEGENOPT(DisableFree , 1, 0) ///< Don't free memory.
CODEGENOPT(DiscardValueNames , 1, 0) ///< Discard Value Names from the IR
(LLVMContext flag)
CODEGENOPT(DisableLLVMPasses , 1, 0) ///< Don't run any LLVM IR passes to get
Index: clang/test/Misc/clear-ast-before-backend.c
===================================================================
--- /dev/null
+++ clang/test/Misc/clear-ast-before-backend.c
@@ -0,0 +1,3 @@
+// RUN: %clang -target x86_64-linux-gnu -c -Xclang -clear-ast-before-backend %s -S
+// RUN: %clang -target x86_64-linux-gnu -c -Xclang -clear-ast-before-backend %s -S -### 2>&1 | FileCheck %s
+// CHECK: "-clear-ast-before-backend"
Index: clang/lib/CodeGen/CodeGenAction.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenAction.cpp
+++ clang/lib/CodeGen/CodeGenAction.cpp
@@ -351,6 +351,11 @@
}
}
+ // FIXME: Fix cleanup issues with clearing the AST when we properly free
+ // things.
+ if (CodeGenOpts.DisableFree && CodeGenOpts.ClearASTBeforeBackend)
+ C.getAllocator().Reset();
+
EmbedBitcode(getModule(), CodeGenOpts, llvm::MemoryBufferRef());
EmitBackendOutput(Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts,
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -5297,6 +5297,9 @@
def disable_free : Flag<["-"], "disable-free">,
HelpText<"Disable freeing of memory on exit">,
MarshallingInfoFlag<FrontendOpts<"DisableFree">>;
+def clear_ast_before_backend : Flag<["-"], "clear-ast-before-backend">,
+ HelpText<"Clear the Clang AST before running backend code generation">,
+ MarshallingInfoFlag<CodeGenOpts<"ClearASTBeforeBackend">>;
def enable_noundef_analysis : Flag<["-"], "enable-noundef-analysis">, Group<f_Group>,
HelpText<"Enable analyzing function argument and return types for mandatory definedness">,
MarshallingInfoFlag<CodeGenOpts<"EnableNoundefAttrs">>;
Index: clang/include/clang/Basic/CodeGenOptions.def
===================================================================
--- clang/include/clang/Basic/CodeGenOptions.def
+++ clang/include/clang/Basic/CodeGenOptions.def
@@ -54,6 +54,7 @@
CODEGENOPT(EnableAIXExtendedAltivecABI, 1, 0) ///< Set for -mabi=vec-extabi. Enables the extended Altivec ABI on AIX.
ENUM_CODEGENOPT(FramePointer, FramePointerKind, 2, FramePointerKind::None) /// frame-pointer: all,non-leaf,none
+CODEGENOPT(ClearASTBeforeBackend , 1, 0) ///< Free the AST before running backend code generation. Only works with -disable-free.
CODEGENOPT(DisableFree , 1, 0) ///< Don't free memory.
CODEGENOPT(DiscardValueNames , 1, 0) ///< Discard Value Names from the IR (LLVMContext flag)
CODEGENOPT(DisableLLVMPasses , 1, 0) ///< Don't run any LLVM IR passes to get
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