Add Mono GC (llvm#35)

llvm/lib/CodeGen/BuiltinGCs.cpp

@@ -112,6 +112,18 @@ class CoreCLRGC : public GCStrategy {
   }
 };
 
+/// A GCStrategy for the Mono Runtime.
+class MonoGC : public GCStrategy {
+public:
+  MonoGC() {
+    UseStatepoints = true;
+    // These options are all gc.root specific, we specify them so that the
+    // gc.root lowering code doesn't run.
+    NeededSafePoints = 0;
+    UsesMetadata = false;
+  }
+};
+
 } // end anonymous namespace
 
 // Register all the above so that they can be found at runtime.  Note that
@@ -125,6 +137,7 @@ static GCRegistry::Add<ShadowStackGC>
 static GCRegistry::Add<StatepointGC> D("statepoint-example",
                                        "an example strategy for statepoint");
 static GCRegistry::Add<CoreCLRGC> E("coreclr", "CoreCLR-compatible GC");
+static GCRegistry::Add<MonoGC> F("mono", "Mono-compatible GC");
 
 // Provide hook to ensure the containing library is fully loaded.
 void llvm::linkAllBuiltinGCs() {}

llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp

@@ -450,8 +450,10 @@ static bool shouldRewriteFunction(Function &F) {
     const auto &FunctionGCName = F.getGC();
     const StringRef StatepointExampleName("statepoint-example");
     const StringRef CoreCLRName("coreclr");
+    const StringRef MonoName("mono");
     return (StatepointExampleName == FunctionGCName) ||
-           (CoreCLRName == FunctionGCName);
+           (CoreCLRName == FunctionGCName) ||
+           (MonoName == FunctionGCName);
   } else
     return false;
 }