Fix GC assertion on array of derived pointers (#47299)

* Fix GC assertion on array of derived pointers

* Add test

(cherry picked from commit d885fc7)

Author: wsmoses

src/llvm-late-gc-lowering.cpp

@@ -419,7 +419,7 @@ unsigned getCompositeNumElements(Type *T) {
 // Walk through a Type, and record the element path to every tracked value inside
 void TrackCompositeType(Type *T, std::vector<unsigned> &Idxs, std::vector<std::vector<unsigned>> &Numberings) {
     if (isa<PointerType>(T)) {
-        if (T->getPointerAddressSpace() == AddressSpace::Tracked)
+        if (isSpecialPtr(T))
             Numberings.push_back(Idxs);
     }
     else if (isa<StructType>(T) || isa<ArrayType>(T) || isa<VectorType>(T)) {

test/llvmpasses/late-lower-gc.ll

@@ -124,6 +124,25 @@ top:
 ; CHECK: ret i32
 }
 
+define void @decayar([2 x {} addrspace(10)* addrspace(11)*] %ar) {
+  %v2 = call {}*** @julia.get_pgcstack()
+  %e0 = extractvalue [2 x {} addrspace(10)* addrspace(11)*] %ar, 0
+  %l0 = load {} addrspace(10)*, {} addrspace(10)* addrspace(11)* %e0
+  %e1 = extractvalue [2 x {} addrspace(10)* addrspace(11)*] %ar, 1
+  %l1 = load {} addrspace(10)*, {} addrspace(10)* addrspace(11)* %e1
+  %r = call i32 @callee_root({} addrspace(10)* %l0, {} addrspace(10)* %l1) 
+  ret void
+}
+
+; CHECK-LABEL: @decayar
+; CHECK:  %gcframe = call {} addrspace(10)** @julia.new_gc_frame(i32 2)
+; CHECK:  %1 = call {} addrspace(10)** @julia.get_gc_frame_slot({} addrspace(10)** %gcframe, i32 1)
+; CHECK:  store {} addrspace(10)* %l0, {} addrspace(10)** %1, align 8
+; CHECK:  %2 = call {} addrspace(10)** @julia.get_gc_frame_slot({} addrspace(10)** %gcframe, i32 0)
+; CHECK: store {} addrspace(10)* %l1, {} addrspace(10)** %2, align 8
+; CHECK: %r = call i32 @callee_root({} addrspace(10)* %l0, {} addrspace(10)* %l1)
+; CHECK: call void @julia.pop_gc_frame({} addrspace(10)** %gcframe)
+
 !0 = !{i64 0, i64 23}
 !1 = !{}
 !2 = distinct !{!2}