[mlir][LLVM] Add support for adding a garbage collector to a LLVM function

This patch simply adds an optional garbage collector attribute to LLVMFuncOp which maps 1:1 to the "gc" property of functions in LLVM.

Differential Revision: https://reviews.llvm.org/D119492

mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td

@@ -1237,6 +1237,7 @@ def LLVM_LLVMFuncOp : LLVM_Op<"func", [
   let arguments = (ins DefaultValuedAttr<Linkage, "Linkage::External">:$linkage,
                    UnitAttr:$dso_local,
                    OptionalAttr<FlatSymbolRefAttr>:$personality,
+                   OptionalAttr<StrAttr>:$garbageCollector,
                    OptionalAttr<ArrayAttr>:$passthrough);
 
   let regions = (region AnyRegion:$body);

mlir/lib/Target/LLVMIR/ConvertFromLLVMIR.cpp

@@ -812,6 +812,9 @@ LogicalResult Importer::processFunction(llvm::Function *f) {
     emitWarning(UnknownLoc::get(context),
                 "could not deduce personality, skipping it");
 
+  if (f->hasGC())
+    fop.setGarbageCollectorAttr(b.getStringAttr(f->getGC()));
+
   if (f->isDeclaration())
     return success();
 

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

@@ -797,6 +797,9 @@ LogicalResult ModuleTranslation::convertOneFunction(LLVMFuncOp func) {
       llvmFunc->setPersonalityFn(pfunc);
   }
 
+  if (auto gc = func.getGarbageCollector())
+    llvmFunc->setGC(gc->str());
+
   // First, create all blocks so we can jump to them.
   llvm::LLVMContext &llvmContext = llvmFunc->getContext();
   for (auto &bb : func) {

mlir/test/Target/LLVMIR/import.ll

@@ -331,6 +331,12 @@ define i32 @invokeLandingpad() personality i8* bitcast (i32 (...)* @__gxx_person
   ret i32 0
 }
 
+; CHECK-LABEL: @hasGCFunction
+; CHECK-SAME: garbageCollector = "statepoint-example"
+define void @hasGCFunction() gc "statepoint-example" {
+    ret void
+}
+
 ;CHECK-LABEL: @useFreezeOp
 define i32 @useFreezeOp(i32 %x) {
   ;CHECK: %{{[0-9]+}} = llvm.freeze %{{[0-9a-z]+}} : i32

mlir/test/Target/LLVMIR/llvmir.mlir

@@ -1378,6 +1378,12 @@ llvm.func @invoke_phis() -> i32 attributes { personality = @__gxx_personality_v0
 
 // -----
 
+// CHECK-LABEL: @hasGCFunction
+// CHECK-SAME: gc "statepoint-example"
+llvm.func @hasGCFunction() attributes { garbageCollector = "statepoint-example" } {
+    llvm.return
+}
+
 // CHECK-LABEL: @callFreezeOp
 llvm.func @callFreezeOp(%x : i32) {
   // CHECK: freeze i32 %{{[0-9]+}}