feat: support closures in batching

src/Ops.jl

@@ -3130,6 +3130,7 @@ end
             [size(input, i) for i in (length(batch_shape) + 1):ndims(input)]...,
         ) for input in inputs
     ]
+    argprefix = gensym("batcharg")
     mlir_fn_res = Reactant.TracedUtils.make_mlir_fn(
         f,
         (sample_inputs...,),
@@ -3138,11 +3139,35 @@ end
         false;
         args_in_result=:none,
         do_transpose=false,
+        argprefix,
     )
 
     func = mlir_fn_res.f
     @assert MLIR.IR.nregions(func) == 1
 
+    if mlir_fn_res.fnwrapped
+        # In the long-term we should be able to do per-argument batching.
+        # Rn we simply broadcast_in_dim the arguments to the correct shape.
+        final_inputs = TracedRArray[]
+        seenargs = Reactant.OrderedIdDict()
+        Reactant.make_tracer(
+            seenargs, f, (argprefix, 1), Reactant.TracedSetPath; toscalar=false
+        )
+        for (k, v) in seenargs
+            v isa Reactant.TracedType || continue
+            bcasted_arg = broadcast_in_dim(
+                v,
+                collect(Int64, (length(batch_shape) + 1):(ndims(v) + length(batch_shape))),
+                vcat(batch_shape, collect(Int64, size(v)));
+                location,
+            )
+            push!(final_inputs, bcasted_arg)
+        end
+        append!(final_inputs, inputs)
+    else
+        final_inputs = inputs
+    end
+
     output_types = MLIR.IR.Type[]
     for result in mlir_fn_res.linear_results
         push!(
@@ -3154,7 +3179,7 @@ end
         )
     end
 
-    return batch(inputs, output_types, batch_shape; fn=func, location)
+    return batch(final_inputs, output_types, batch_shape; fn=func, location)
 end
 
 @noinline function batch(

test/batching.jl

@@ -85,3 +85,18 @@ end
 
     run_auto_batching_tests(naive_batched_matmul, x, y)
 end
+
+function batch_with_closure(x, y)
+    _fn(x) = x .+ y
+    return mapslices(_fn, x; dims=2)
+end
+
+@testset "Batching with closure" begin
+    x = Reactant.TestUtils.construct_test_array(Float32, 3, 256, 8)
+    y = Reactant.TestUtils.construct_test_array(Float32, 256)
+
+    x_ra = Reactant.to_rarray(x)
+    y_ra = Reactant.to_rarray(y)
+
+    @test @jit(batch_with_closure(x_ra, y_ra)) ≈ batch_with_closure(x, y)
+end