aeubanks updated this revision to Diff 411851.
aeubanks added a comment.
reword
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D120666/new/
https://reviews.llvm.org/D120666
Files:
clang/docs/ClangPlugins.rst
Index: clang/docs/ClangPlugins.rst
===================================================================
--- clang/docs/ClangPlugins.rst
+++ clang/docs/ClangPlugins.rst
@@ -200,3 +200,17 @@
PluginASTAction::ActionType getActionType() override {
return AddAfterMainAction;
}
+
+Interaction with ``-clear-ast-before-backend``
+----------------------------------------------
+
+To reduce peak memory usage of the compiler, plugins are recommended to run
+*before* the main action, which is usually code generation. This is because
+having any plugins that run after the codegen action automatically turns off
+``-clear-ast-before-backend``. ``-clear-ast-before-backend`` reduces peak
+memory by clearing the Clang AST after generating IR and before running IR
+optimizations. Use ``CmdlineBeforeMainAction`` or ``AddBeforeMainAction`` as
+``getActionType`` to run plugins while still benefitting from
+``-clear-ast-before-backend``. Plugins must make sure not to modify the AST,
+otherwise they should run after the main action.
+
Index: clang/docs/ClangPlugins.rst
===================================================================
--- clang/docs/ClangPlugins.rst
+++ clang/docs/ClangPlugins.rst
@@ -200,3 +200,17 @@
PluginASTAction::ActionType getActionType() override {
return AddAfterMainAction;
}
+
+Interaction with ``-clear-ast-before-backend``
+----------------------------------------------
+
+To reduce peak memory usage of the compiler, plugins are recommended to run
+*before* the main action, which is usually code generation. This is because
+having any plugins that run after the codegen action automatically turns off
+``-clear-ast-before-backend``. ``-clear-ast-before-backend`` reduces peak
+memory by clearing the Clang AST after generating IR and before running IR
+optimizations. Use ``CmdlineBeforeMainAction`` or ``AddBeforeMainAction`` as
+``getActionType`` to run plugins while still benefitting from
+``-clear-ast-before-backend``. Plugins must make sure not to modify the AST,
+otherwise they should run after the main action.
+
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