Treat getproperty(::Module, ::Symbol) like GlobalRefs

Author: serenity4

src/codegen/reverse.jl

@@ -289,6 +289,8 @@ function diffract_ir!(ir, ci, meth, sparams::Core.SimpleVector, nargs::Int, N::I
             if isa(stmt, Core.ReturnNode)
                 accum!(stmt.val, Argument(2))
                 current_env = nothing
+            elseif is_global_access(ir, stmt)
+                # Treat it as a GlobalRef, dropping gradients.
             elseif isexpr(stmt, :call) || isexpr(stmt, :invoke)
                 Δ = do_accum(SSAValue(i))
                 callee = retrieve_ctx_obj(current_env, i)
@@ -453,7 +455,9 @@ function diffract_ir!(ir, ci, meth, sparams::Core.SimpleVector, nargs::Int, N::I
             end
             stmt = urs[]
 
-            if isexpr(stmt, :call)
+            if is_global_access(ir, stmt)
+                fwds[i] = ZeroTangent()
+            elseif isexpr(stmt, :call)
                 callee = insert_node_here!(Expr(:call, getfield, Argument(1), i))
                 pushfirst!(stmt.args, callee)
                 call = insert_node_here!(stmt)
@@ -565,7 +569,7 @@ function diffract_ir!(ir, ci, meth, sparams::Core.SimpleVector, nargs::Int, N::I
         if isexpr(stmt, :(=))
             stmt = stmt.args[2]
         end
-        if isexpr(stmt, :call)
+        if isexpr(stmt, :call) && !is_global_access(compact, stmt)
             compact[SSAValue(idx)] = Expr(:call, ∂⃖{N}(), stmt.args...)
             if isexpr(orig_stmt, :(=))
                 orig_stmt.args[2] = stmt
@@ -677,3 +681,18 @@ function diffract_ir!(ir, ci, meth, sparams::Core.SimpleVector, nargs::Int, N::I
 
     return ir
 end
+
+eval_globalref(x) = x
+eval_globalref(x::GlobalRef) = getglobal(x.mod, x.name)
+ssa_def(ir, idx::SSAValue) = ssa_def(ir, ir[idx][:inst])
+ssa_def(ir, def) = def
+
+function is_global_access(ir::Union{IRCode,IncrementalCompact}, stmt)
+    isexpr(stmt, :call, 3) || return false
+    f = eval_globalref(ssa_def(ir, stmt.args[1]))
+    f === getproperty || return false
+    from = eval_globalref(ssa_def(ir, stmt.args[2]))
+    isa(from, Module) || return false
+    name = stmt.args[3]
+    isa(name, QuoteNode) && isa(name.value, Symbol)
+end