Compile now can attach arbitrary data to an entry (#2634)

mlx/compile.cpp

@@ -296,6 +296,7 @@ class CompilerCache {
     std::vector<array> tape;
     bool empty{true};
     std::vector<uint64_t> constants;
+    std::shared_ptr<void> extra;
   };
 
   // Returns a reference to a CacheEntry which can be updated
@@ -376,8 +377,9 @@ CompilerCache& compiler_cache() {
   return compiler_cache_;
 }
 
-std::pair<std::vector<array>, std::vector<array>> compile_trace(
-    const std::function<std::vector<array>(const std::vector<array>&)>& fun,
+std::tuple<std::vector<array>, std::vector<array>, std::shared_ptr<void>>
+compile_trace(
+    const ArrayFnWithExtra& fun,
     const std::vector<array>& inputs,
     bool shapeless) {
   // Set the global tracing flag.
@@ -391,7 +393,9 @@ std::pair<std::vector<array>, std::vector<array>> compile_trace(
     in.set_tracer(true);
     tracer_inputs.push_back(std::move(in));
   }
-  return {tracer_inputs, fun(tracer_inputs)};
+
+  auto output = fun(tracer_inputs);
+  return {tracer_inputs, output.first, output.second};
 }
 
 // Traverses the graph to build a tape and a map of array ids to their parents
@@ -932,8 +936,8 @@ bool skip_compile() {
       !(compile_available_for_device(default_device()));
 }
 
-std::function<std::vector<array>(const std::vector<array>&)> compile(
-    std::function<std::vector<array>(const std::vector<array>&)> fun,
+ArrayFnWithExtra compile(
+    ArrayFnWithExtra fun,
     std::uintptr_t fun_id,
     bool shapeless /* = false */,
     std::vector<uint64_t> constants /* = {} */) {
@@ -966,7 +970,7 @@ std::function<std::vector<array>(const std::vector<array>&)> compile(
       // Set the constants
       entry.constants = std::move(constants);
       // Trace to build the graph
-      std::tie(entry.inputs, entry.outputs) =
+      std::tie(entry.inputs, entry.outputs, entry.extra) =
           compile_trace(fun, inputs, shapeless);
 
       // DFS the graph and get a tape, and a map of array id to (parent,
@@ -991,8 +995,37 @@ std::function<std::vector<array>(const std::vector<array>&)> compile(
 
     // At this point we must have a tape, now replace the placeholders
     // with real arrays that can be evaluated
-    return compile_replace(
-        entry.tape, entry.inputs, entry.outputs, inputs, shapeless);
+    return ArraysAndExtra{
+        compile_replace(
+            entry.tape, entry.inputs, entry.outputs, inputs, shapeless),
+        entry.extra};
+  };
+}
+
+std::function<std::vector<array>(const std::vector<array>&)> compile(
+    std::function<std::vector<array>(const std::vector<array>&)> fun,
+    std::uintptr_t fun_id,
+    bool shapeless /* = false */,
+    std::vector<uint64_t> constants /* = {} */) {
+  if (skip_compile()) {
+    return fun;
+  }
+  if (!fun) {
+    throw std::invalid_argument(
+        "[compile] Cannot compile a function without a target.");
+  }
+
+  ArrayFnWithExtra fun_with_extra =
+      [fun = std::move(fun)](const std::vector<array>& inputs) {
+        return ArraysAndExtra{fun(inputs), nullptr};
+      };
+
+  auto compiled_fun = compile(
+      std::move(fun_with_extra), fun_id, shapeless, std::move(constants));
+
+  return [compiled_fun =
+              std::move(compiled_fun)](const std::vector<array>& inputs) {
+    return compiled_fun(inputs).first;
   };
 }
 

mlx/compile_impl.h

@@ -8,6 +8,10 @@
 
 namespace mlx::core::detail {
 
+using ArraysAndExtra = std::pair<std::vector<array>, std::shared_ptr<void>>;
+using ArrayFnWithExtra =
+    std::function<ArraysAndExtra(const std::vector<array>&)>;
+
 // This is not part of the general C++ API as calling with a bad id is a bad
 // idea.
 std::function<std::vector<array>(const std::vector<array>&)> compile(
@@ -16,6 +20,12 @@ std::function<std::vector<array>(const std::vector<array>&)> compile(
     bool shapeless = false,
     std::vector<uint64_t> constants = {});
 
+ArrayFnWithExtra compile(
+    ArrayFnWithExtra fun,
+    std::uintptr_t fun_id,
+    bool shapeless,
+    std::vector<uint64_t> constants);
+
 // Erase cached compile functions
 void compile_erase(std::uintptr_t fun_id);
 
@@ -25,8 +35,9 @@ void compile_clear_cache();
 
 bool compile_available_for_device(const Device& device);
 
-std::pair<std::vector<array>, std::vector<array>> compile_trace(
-    const std::function<std::vector<array>(const std::vector<array>&)>& fun,
+std::tuple<std::vector<array>, std::vector<array>, std::shared_ptr<void>>
+compile_trace(
+    const ArrayFnWithExtra& fun,
     const std::vector<array>& inputs,
     bool shapeless);
 

mlx/export.cpp

@@ -579,11 +579,11 @@ void FunctionExporter::export_function(const Args& args, const Kwargs& kwargs) {
     for (auto& k : kwarg_keys) {
       kwargs.insert({k, *it++});
     }
-    return fun(args, kwargs);
+    return detail::ArraysAndExtra{fun(args, kwargs), nullptr};
   };
 
   // Trace to build the graph
-  auto [trace_inputs, trace_outputs] =
+  auto [trace_inputs, trace_outputs, extra] =
       detail::compile_trace(flat_fun, inputs, ftable->shapeless);
 
   // DFS the graph and get the tape