Index: bindings/ocaml/llvm/llvm_ocaml.c
===================================================================
--- bindings/ocaml/llvm/llvm_ocaml.c
+++ bindings/ocaml/llvm/llvm_ocaml.c
@@ -2539,8 +2539,24 @@
   return Val_bool(LLVMFinalizeFunctionPassManager(FPM));
 }
 
+/* (LLVM.PassManager.t, (string -> bool)) list
+   Holds all the closures that */
+extern value *active_closures_list;
+
 /* PassManager.any PassManager.t -> unit */
 CAMLprim value llvm_passmanager_dispose(LLVMPassManagerRef PM) {
+
+  // We drop any closures associated with this PassManager. The closures will
+  // then be GCed
+  static value *drop_closure_f = NULL;
+  if (drop_closure_f == NULL) {
+    drop_closure_f = caml_named_value("ll_drop_closure");
+  }
+  if (active_closures_list != NULL) {
+    *active_closures_list =
+        caml_callback2(*drop_closure_f, *active_closures_list, (value)PM);
+  }
+
   LLVMDisposePassManager(PM);
   return Val_unit;
 }
Index: bindings/ocaml/transforms/ipo/ipo_ocaml.c
===================================================================
--- bindings/ocaml/transforms/ipo/ipo_ocaml.c
+++ bindings/ocaml/transforms/ipo/ipo_ocaml.c
@@ -15,9 +15,15 @@
 |*                                                                            *|
 \*===----------------------------------------------------------------------===*/
 
-#include "llvm-c/Transforms/IPO.h"
-#include "caml/mlvalues.h"
+#include "caml/alloc.h"
+#include "caml/callback.h"
+#include "caml/fail.h"
+#include "caml/memory.h"
 #include "caml/misc.h"
+#include "caml/mlvalues.h"
+#include "llvm-c/Core.h"
+#include "llvm-c/Transforms/IPO.h"
+#include <assert.h>
 
 /* [`Module] Llvm.PassManager.t -> unit */
 CAMLprim value llvm_add_argument_promotion(LLVMPassManagerRef PM) {
@@ -91,6 +97,57 @@
   return Val_unit;
 }
 
+/* (LLVM.PassManager.t, (string -> bool)) list
+   Memory managed by OCaml GC*/
+value *active_closures_list = NULL;
+
+LLVMBool MustPreserveCallBack(LLVMValueRef Val, void *Ctx) {
+  CAMLparam0();
+  CAMLlocal2(LLVMValName, Predicate);
+  const char *llvmValName;
+  LLVMBool ret;
+  LLVMPassManagerRef PM = (LLVMPassManagerRef)Ctx;
+  static value *find_closure_f = NULL;
+  if (find_closure_f == NULL) {
+    find_closure_f = caml_named_value("ll_find_closure");
+  }
+  Predicate = caml_callback2(*find_closure_f, *active_closures_list, (value)PM);
+  llvmValName = LLVMGetValueName(Val);
+  LLVMValName = caml_copy_string(llvmValName);
+  ret = Bool_val(caml_callback(Predicate, LLVMValName));
+
+  CAMLreturnT(LLVMBool, ret);
+}
+
+/* [`Module] Llvm.PassManager.t -> (string -> bool) -> unit */
+CAMLprim value llvm_add_internalize_predicate(LLVMPassManagerRef PM,
+                                              value Predicate) {
+  CAMLparam1(Predicate);
+  if (active_closures_list == NULL) {
+    // initialize the active_closure_list
+    active_closures_list = malloc(sizeof(value));
+    if (active_closures_list == NULL)
+      caml_raise_out_of_memory();
+    *active_closures_list = Val_emptylist;
+    caml_register_global_root(active_closures_list);
+  }
+
+  static value *add_or_replace_closure_f = NULL;
+  if (add_or_replace_closure_f == NULL) {
+    add_or_replace_closure_f = caml_named_value("ll_add_or_replace_closure");
+  }
+  *active_closures_list = caml_callback3(
+      *add_or_replace_closure_f, *active_closures_list, (value)PM, Predicate);
+
+  /* We can't directly pass the Predicate value to the callback as GC might move
+     it
+     before callback calls it. So we pass it the PM pointer, which is not GC
+     dependant. */
+  LLVMAddInternalizePassWithMustPreservePredicate(PM, PM,
+                                                  &MustPreserveCallBack);
+  CAMLreturn(Val_unit);
+}
+
 /* [`Module] Llvm.PassManager.t -> unit */
 CAMLprim value llvm_add_strip_dead_prototypes(LLVMPassManagerRef PM) {
   LLVMAddStripDeadPrototypesPass(PM);
Index: bindings/ocaml/transforms/ipo/llvm_ipo.ml
===================================================================
--- bindings/ocaml/transforms/ipo/llvm_ipo.ml
+++ bindings/ocaml/transforms/ipo/llvm_ipo.ml
@@ -42,9 +42,42 @@
 external add_internalize
   : [ `Module ] Llvm.PassManager.t -> all_but_main:bool -> unit
   = "llvm_add_internalize"
+external add_internalize_predicate
+  : [ `Module ] Llvm.PassManager.t -> (string -> bool) -> unit
+  = "llvm_add_internalize_predicate"
 external add_strip_dead_prototypes
   : [ `Module ] Llvm.PassManager.t -> unit
   = "llvm_add_strip_dead_prototypes"
 external add_strip_symbols
   : [ `Module ] Llvm.PassManager.t -> unit
   = "llvm_add_strip_symbols"
+
+
+(* Helper functions for add_internalize_predicate. Used by the C code *)
+let add_or_replace_closure :
+       ([`Module] Llvm.PassManager.t * (string -> bool)) list
+    -> [`Module] Llvm.PassManager.t
+    -> (string -> bool)
+    -> ([`Module] Llvm.PassManager.t * (string -> bool)) list =
+ fun ls pm c -> (pm, c) :: List.filter (fun (pm', _) -> pm' == pm) ls
+
+let rec find_closure :
+       ([`Module] Llvm.PassManager.t * (string -> bool)) list
+    -> [`Module] Llvm.PassManager.t
+    -> string
+    -> bool =
+ fun ls pm ->
+  match ls with
+  | [] -> assert false
+  | (pm', c) :: _ when pm' == pm -> c
+  | head :: tail -> find_closure tail pm
+
+let drop_closure :
+       ([`Module] Llvm.PassManager.t * (string -> bool)) list
+    -> [`Module] Llvm.PassManager.t
+    -> ([`Module] Llvm.PassManager.t * (string -> bool)) list =
+ fun ls pm -> List.filter (fun (pm', _) -> pm' == pm) ls
+
+let _ = Callback.register "ll_add_or_replace_closure" add_or_replace_closure
+let _ = Callback.register "ll_find_closure" find_closure
+let _ = Callback.register "ll_drop_closure" drop_closure
Index: bindings/ocaml/transforms/ipo/llvm_ipo.mli
===================================================================
--- bindings/ocaml/transforms/ipo/llvm_ipo.mli
+++ bindings/ocaml/transforms/ipo/llvm_ipo.mli
@@ -71,6 +71,11 @@
   : [ `Module ] Llvm.PassManager.t -> all_but_main:bool -> unit
   = "llvm_add_internalize"
 
+(** See the [llvm::createInternalizePass] function.
+    If predicate returns [true], that symbol is preserved. *)
+val add_internalize_predicate
+  : [ `Module ] Llvm.PassManager.t -> (string -> bool) -> unit
+
 (** See the [llvm::createStripDeadPrototypesPass] function. *)
 external add_strip_dead_prototypes
   : [ `Module ] Llvm.PassManager.t -> unit