[PATCH] D142169: [RS4GC] Add a GCStrategy option to enable RS4GC

[Campbell Suter via Phabricator via llvm-commits]

znix created this revision.
znix added reviewers: dantrushin, reames, mkazantsev.
Herald added subscribers: StephenFan, hiraditya.
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Herald added a project: LLVM.
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Currently, the RewriteStatepointsForGC pass has a hardcoded list of GC
strategies that it operates on, forcing downstream projects to patch
LLVM to enable it for their own strategies. The diff D141110 <https://reviews.llvm.org/D141110> changes
that to each GCStrategy having a flag to enable or disable RS4GC.

This patch adds that flag. It currently doesn't do anything, but is
provided so downstream projects can enable it to smooth the transition.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D142169

Files:
  llvm/include/llvm/IR/GCStrategy.h
  llvm/lib/IR/BuiltinGCs.cpp


Index: llvm/lib/IR/BuiltinGCs.cpp
===================================================================
--- llvm/lib/IR/BuiltinGCs.cpp
+++ llvm/lib/IR/BuiltinGCs.cpp
@@ -66,6 +66,7 @@
 public:
   StatepointGC() {
     UseStatepoints = true;
+    UseRS4GC = true;
     // These options are all gc.root specific, we specify them so that the
     // gc.root lowering code doesn't run.
     NeededSafePoints = false;
@@ -98,6 +99,7 @@
 public:
   CoreCLRGC() {
     UseStatepoints = true;
+    UseRS4GC = true;
     // These options are all gc.root specific, we specify them so that the
     // gc.root lowering code doesn't run.
     NeededSafePoints = false;
Index: llvm/include/llvm/IR/GCStrategy.h
===================================================================
--- llvm/include/llvm/IR/GCStrategy.h
+++ llvm/include/llvm/IR/GCStrategy.h
@@ -68,8 +68,13 @@
 
 protected:
   bool UseStatepoints = false; /// Uses gc.statepoints as opposed to gc.roots,
-                               /// if set, none of the other options can be
-                               /// anything but their default values.
+                               /// if set, NeededSafePoints and UsesMetadata
+                               /// should be left at their default values.
+
+  bool UseRS4GC = false; /// If UseStatepoints is set, this determines whether
+                         /// the RewriteStatepointsForGC pass should rewrite
+                         /// this function's calls.
+                         /// This should only be set if UseStatepoints is set.
 
   bool NeededSafePoints = false;    ///< if set, calls are inferred to be safepoints
   bool UsesMetadata = false;     ///< If set, backend must emit metadata tables.
@@ -96,6 +101,15 @@
   virtual std::optional<bool> isGCManagedPointer(const Type *Ty) const {
     return std::nullopt;
   }
+
+  /// Returns true if the RewriteStatepointsForGC pass should run on functions
+  /// using this GC.
+  bool useRS4GC() const {
+    return UseRS4GC;
+    assert(useStatepoints() &&
+           "GC strategy has useRS4GC but not useStatepoints set");
+  }
+
   ///@}
 
   /// If set, appropriate metadata tables must be emitted by the back-end


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