diff --git a/src/ir/intrinsics.cpp b/src/ir/intrinsics.cpp
index 26b62439118..b485aa70a64 100644
--- a/src/ir/intrinsics.cpp
+++ b/src/ir/intrinsics.cpp
@@ -20,7 +20,8 @@
 namespace wasm {
 
 static Name BinaryenIntrinsicsModule("binaryen-intrinsics"),
-  CallWithoutEffects("call.without.effects");
+  CallWithoutEffects("call.without.effects"),
+  JSPrototypesModule("wasm:js-prototypes"), ConfigureAll("configureAll");
 
 bool Intrinsics::isCallWithoutEffects(Function* func) {
   if (func->module != BinaryenIntrinsicsModule) {
@@ -45,4 +46,58 @@ Call* Intrinsics::isCallWithoutEffects(Expression* curr) {
   return nullptr;
 }
 
+bool Intrinsics::isConfigureAll(Function* func) {
+  return func->module == JSPrototypesModule && func->base == ConfigureAll;
+}
+
+Call* Intrinsics::isConfigureAll(Expression* curr) {
+  if (auto* call = curr->dynCast<Call>()) {
+    if (auto* func = module.getFunctionOrNull(call->target)) {
+      if (isConfigureAll(func)) {
+        return call;
+      }
+    }
+  }
+  return nullptr;
+}
+
+std::vector<Name> Intrinsics::getConfigureAllFunctions(Call* call) {
+  assert(isConfigureAll(call));
+
+  auto error = [&](const char* msg) {
+    Fatal() << "Invalid configureAll( " << msg << "): " << *call;
+  };
+
+  // The second operand is an array of signature-called function refs.
+  auto& operands = call->operands;
+  if (operands.size() <= 2) {
+    error("insufficient operands");
+  }
+  auto* arrayNew = operands[1]->dynCast<ArrayNewElem>();
+  if (!arrayNew) {
+    error("not array.new_elem");
+  }
+  auto start = arrayNew->offset->dynCast<Const>();
+  if (!start || start->value.geti32() != 0) {
+    error("start != 0");
+  }
+  auto size = arrayNew->size->dynCast<Const>();
+  if (!size) {
+    error("size not const");
+  }
+  auto* seg = module.getElementSegment(arrayNew->segment);
+  if (seg->data.size() != size->value.getUnsigned()) {
+    error("wrong seg size");
+  }
+  std::vector<Name> ret;
+  for (auto* curr : seg->data) {
+    if (auto* refFunc = curr->dynCast<RefFunc>()) {
+      ret.push_back(refFunc->func);
+    } else {
+      error("non-function ref");
+    }
+  }
+  return ret;
+}
+
 } // namespace wasm
diff --git a/src/ir/intrinsics.h b/src/ir/intrinsics.h
index 9a1356029ac..c06eb832677 100644
--- a/src/ir/intrinsics.h
+++ b/src/ir/intrinsics.h
@@ -21,7 +21,8 @@
 #include "wasm-traversal.h"
 
 //
-// See the README.md for background on intrinsic functions.
+// Intrinsics include Binaryen intrinsics, and Wasm spec builtins. See the
+// README.md for more.
 //
 // Intrinsics can be recognized by Intrinsics::isFoo() methods, that check if a
 // function is a particular intrinsic, or if a call to a function is so. The
@@ -37,8 +38,7 @@ class Intrinsics {
 public:
   Intrinsics(Module& module) : module(module) {}
 
-  //
-  // Check if an instruction is the call.without.effects intrinsic.
+  // Check if an instruction is the Binaryen call.without.effects intrinsic.
   //
   //   (import "binaryen-intrinsics" "call.without.effects"
   //     (func (..params..) (param $target funcref) (..results..)))
@@ -85,9 +85,30 @@ class Intrinsics {
   //
   // Later passes will then turn that into a direct call and further optimize
   // things.
-  //
   bool isCallWithoutEffects(Function* func);
   Call* isCallWithoutEffects(Expression* curr);
+
+  // Check if an instruction is the wasm/JS interop configureAll builtin. Such
+  // calls have a second parameter which is an array of function references,
+  // which must be assumed to be "signature-called": Called from outside the
+  // module, using that signature. "Signature-called" is less powerful than the
+  // reference to the function generally escaping, as we do not care about the
+  // heap type of the function (no call_refs or casts will happen), all we know
+  // is that a JS-style call of the methods can occur (and only the signature
+  // matters then).
+  bool isConfigureAll(Function* func);
+  Call* isConfigureAll(Expression* curr);
+  // Given a configureAll, return all the functions it refers to. We error if it
+  // is not in the canonical form
+  //
+  //  (call $configureAll
+  //    ..arg0..
+  //    (array.new_elem $seg (0) (N)
+  //    ..
+  //  )
+  //
+  // where the segment $seg is of size N.
+  std::vector<Name> getConfigureAllFunctions(Call* call);
 };
 
 } // namespace wasm
diff --git a/src/ir/module-utils.cpp b/src/ir/module-utils.cpp
index 5abbbecc01d..0dd3342f0d8 100644
--- a/src/ir/module-utils.cpp
+++ b/src/ir/module-utils.cpp
@@ -15,6 +15,7 @@
  */
 
 #include "module-utils.h"
+#include "ir/find_all.h"
 #include "ir/intrinsics.h"
 #include "ir/manipulation.h"
 #include "ir/metadata.h"
@@ -692,6 +693,26 @@ std::vector<HeapType> getPublicHeapTypes(Module& wasm) {
     WASM_UNREACHABLE("unexpected export kind");
   }
 
+  // ConfigureAll in a start function makes its functions callable. They are
+  // only signature-called, so the heap type does not need to be public - nor
+  // types referred to - but for now we mark them as public to avoid breakage in
+  // several passes.
+  // TODO Specific fixes in those passes could replace this, and allow better
+  //      optimization.
+  if (wasm.start) {
+    auto* start = wasm.getFunction(wasm.start);
+    if (!start->imported()) {
+      Intrinsics intrinsics(wasm);
+      for (auto* call : FindAll<Call>(start->body).list) {
+        if (intrinsics.isConfigureAll(call)) {
+          for (auto func : intrinsics.getConfigureAllFunctions(call)) {
+            notePublic(wasm.getFunction(func)->type.getHeapType());
+          }
+        }
+      }
+    }
+  }
+
   // Ignorable public types are public.
   for (auto type : getIgnorablePublicTypes()) {
     notePublic(type);
diff --git a/src/passes/RemoveUnusedModuleElements.cpp b/src/passes/RemoveUnusedModuleElements.cpp
index cf933c639f4..0da263c7758 100644
--- a/src/passes/RemoveUnusedModuleElements.cpp
+++ b/src/passes/RemoveUnusedModuleElements.cpp
@@ -136,7 +136,8 @@ struct Noter : public PostWalker<Noter, UnifiedExpressionVisitor<Noter>> {
   void visitCall(Call* curr) {
     use({ModuleElementKind::Function, curr->target});
 
-    if (Intrinsics(*getModule()).isCallWithoutEffects(curr)) {
+    Intrinsics intrinsics(*getModule());
+    if (intrinsics.isCallWithoutEffects(curr)) {
       // A call-without-effects receives a function reference and calls it, the
       // same as a CallRef. When we have a flag for non-closed-world, we should
       // handle this automatically by the reference flowing out to an import,
@@ -157,6 +158,12 @@ struct Noter : public PostWalker<Noter, UnifiedExpressionVisitor<Noter>> {
         callRef.target = target;
         visitCallRef(&callRef);
       }
+    } else if (intrinsics.isConfigureAll(curr)) {
+      // Every function that configureAll refers to is signature-called. Mark
+      // them all as called, as JS can call them.
+      for (auto func : intrinsics.getConfigureAllFunctions(curr)) {
+        use({ModuleElementKind::Function, func});
+      }
     }
   }
 
diff --git a/test/lit/passes/remove-unused-module-elements-configureAll.wast b/test/lit/passes/remove-unused-module-elements-configureAll.wast
new file mode 100644
index 00000000000..c728b77c69e
--- /dev/null
+++ b/test/lit/passes/remove-unused-module-elements-configureAll.wast
@@ -0,0 +1,137 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+
+;; RUN: foreach %s %t wasm-opt --remove-unused-module-elements --closed-world -all -S -o - | filecheck %s
+;; RUN: foreach %s %t wasm-opt --remove-unused-module-elements                -all -S -o - | filecheck %s --check-prefix OPEN_WORLD
+
+;; Test that configureAll is respected: referred functions are not optimized
+;; away or emptied out. This is so even in closed world.
+
+(module
+  ;; CHECK:      (type $externs (array (mut externref)))
+  ;; OPEN_WORLD:      (type $externs (array (mut externref)))
+  (type $externs (array (mut externref)))
+
+  ;; CHECK:      (type $funcs (array (mut funcref)))
+  ;; OPEN_WORLD:      (type $funcs (array (mut funcref)))
+  (type $funcs (array (mut funcref)))
+
+  ;; CHECK:      (type $bytes (array (mut i8)))
+  ;; OPEN_WORLD:      (type $bytes (array (mut i8)))
+  (type $bytes (array (mut i8)))
+
+  ;; CHECK:      (type $configureAll (func (param (ref null $externs) (ref null $funcs) (ref null $bytes) externref)))
+  ;; OPEN_WORLD:      (type $configureAll (func (param (ref null $externs) (ref null $funcs) (ref null $bytes) externref)))
+  (type $configureAll (func (param (ref null $externs)) (param (ref null $funcs)) (param (ref null $bytes)) (param externref)))
+
+  ;; CHECK:      (type $4 (func))
+
+  ;; CHECK:      (type $5 (func (result i32)))
+
+  ;; CHECK:      (type $6 (func (param i32) (result i32)))
+
+  ;; CHECK:      (import "wasm:js-prototypes" "configureAll" (func $configureAll (type $configureAll) (param (ref null $externs) (ref null $funcs) (ref null $bytes) externref)))
+  ;; OPEN_WORLD:      (type $4 (func))
+
+  ;; OPEN_WORLD:      (type $5 (func (result i32)))
+
+  ;; OPEN_WORLD:      (type $6 (func (param i32) (result i32)))
+
+  ;; OPEN_WORLD:      (import "wasm:js-prototypes" "configureAll" (func $configureAll (type $configureAll) (param (ref null $externs) (ref null $funcs) (ref null $bytes) externref)))
+  (import "wasm:js-prototypes" "configureAll" (func $configureAll (type $configureAll)))
+
+  ;; CHECK:      (data $bytes "12345678")
+
+  ;; CHECK:      (elem $externs externref (item (ref.null noextern)))
+  ;; OPEN_WORLD:      (data $bytes "12345678")
+
+  ;; OPEN_WORLD:      (elem $externs externref (item (ref.null noextern)))
+  (elem $externs externref
+    (ref.null extern)
+  )
+
+  ;; CHECK:      (elem $funcs func $foo $bar)
+  ;; OPEN_WORLD:      (elem $funcs func $foo $bar)
+  (elem $funcs funcref
+    (ref.func $foo)
+    (ref.func $bar)
+  )
+
+  (data $bytes "12345678")
+
+  ;; CHECK:      (start $start)
+  ;; OPEN_WORLD:      (start $start)
+  (start $start)
+
+  ;; CHECK:      (func $start (type $4)
+  ;; CHECK-NEXT:  (call $configureAll
+  ;; CHECK-NEXT:   (array.new_elem $externs $externs
+  ;; CHECK-NEXT:    (i32.const 0)
+  ;; CHECK-NEXT:    (i32.const 1)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (array.new_elem $funcs $funcs
+  ;; CHECK-NEXT:    (i32.const 0)
+  ;; CHECK-NEXT:    (i32.const 2)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (array.new_data $bytes $bytes
+  ;; CHECK-NEXT:    (i32.const 0)
+  ;; CHECK-NEXT:    (i32.const 8)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (ref.null noextern)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  ;; OPEN_WORLD:      (func $start (type $4)
+  ;; OPEN_WORLD-NEXT:  (call $configureAll
+  ;; OPEN_WORLD-NEXT:   (array.new_elem $externs $externs
+  ;; OPEN_WORLD-NEXT:    (i32.const 0)
+  ;; OPEN_WORLD-NEXT:    (i32.const 1)
+  ;; OPEN_WORLD-NEXT:   )
+  ;; OPEN_WORLD-NEXT:   (array.new_elem $funcs $funcs
+  ;; OPEN_WORLD-NEXT:    (i32.const 0)
+  ;; OPEN_WORLD-NEXT:    (i32.const 2)
+  ;; OPEN_WORLD-NEXT:   )
+  ;; OPEN_WORLD-NEXT:   (array.new_data $bytes $bytes
+  ;; OPEN_WORLD-NEXT:    (i32.const 0)
+  ;; OPEN_WORLD-NEXT:    (i32.const 8)
+  ;; OPEN_WORLD-NEXT:   )
+  ;; OPEN_WORLD-NEXT:   (ref.null noextern)
+  ;; OPEN_WORLD-NEXT:  )
+  ;; OPEN_WORLD-NEXT: )
+  (func $start
+    (call $configureAll
+      (array.new_elem $externs $externs
+        (i32.const 0) (i32.const 1))
+      (array.new_elem $funcs $funcs
+        (i32.const 0) (i32.const 2))
+      (array.new_data $bytes $bytes
+        (i32.const 0) (i32.const 8))
+      (ref.null extern)
+    )
+  )
+
+  ;; CHECK:      (func $foo (type $5) (result i32)
+  ;; CHECK-NEXT:  (i32.const 42)
+  ;; CHECK-NEXT: )
+  ;; OPEN_WORLD:      (func $foo (type $5) (result i32)
+  ;; OPEN_WORLD-NEXT:  (i32.const 42)
+  ;; OPEN_WORLD-NEXT: )
+  (func $foo (result i32)
+    ;; configureAll keeps this from being modified.
+    (i32.const 42)
+  )
+
+  ;; CHECK:      (func $bar (type $6) (param $x i32) (result i32)
+  ;; CHECK-NEXT:  (local.get $x)
+  ;; CHECK-NEXT: )
+  ;; OPEN_WORLD:      (func $bar (type $6) (param $x i32) (result i32)
+  ;; OPEN_WORLD-NEXT:  (local.get $x)
+  ;; OPEN_WORLD-NEXT: )
+  (func $bar (param $x i32) (result i32)
+    ;; This too.
+    (local.get $x)
+  )
+
+  (func $unconfigured (result i32)
+    ;; This is not referred to by configureAll, and can be removed.
+    (i32.const 1337)
+  )
+)
diff --git a/test/lit/passes/signature-refining-configureAll.wast b/test/lit/passes/signature-refining-configureAll.wast
new file mode 100644
index 00000000000..48ca0dfffd9
--- /dev/null
+++ b/test/lit/passes/signature-refining-configureAll.wast
@@ -0,0 +1,171 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+
+;; RUN: foreach %s %t wasm-opt --signature-refining --closed-world -all -S -o - | filecheck %s
+;; RUN: foreach %s %t wasm-opt --signature-refining                -all -S -o - | filecheck %s --check-prefix OPEN_WORLD
+
+;; Test that configureAll is respected: referred functions are not refined.
+;; This is so even in closed world.
+
+(module
+  ;; CHECK:      (type $externs (array (mut externref)))
+  ;; OPEN_WORLD:      (type $externs (array (mut externref)))
+  (type $externs (array (mut externref)))
+
+  ;; CHECK:      (type $funcs (array (mut funcref)))
+  ;; OPEN_WORLD:      (type $funcs (array (mut funcref)))
+  (type $funcs (array (mut funcref)))
+
+  ;; CHECK:      (type $bytes (array (mut i8)))
+  ;; OPEN_WORLD:      (type $bytes (array (mut i8)))
+  (type $bytes (array (mut i8)))
+
+  ;; CHECK:      (rec
+  ;; CHECK-NEXT:  (type $ret-any-2 (func (result (ref (exact $struct)))))
+
+  ;; CHECK:       (type $struct (struct))
+
+  ;; CHECK:       (type $5 (func))
+
+  ;; CHECK:      (type $configureAll (func (param (ref null $externs) (ref null $funcs) (ref null $bytes) externref)))
+  ;; OPEN_WORLD:      (rec
+  ;; OPEN_WORLD-NEXT:  (type $ret-any-2 (func (result (ref (exact $struct)))))
+
+  ;; OPEN_WORLD:       (type $struct (struct))
+
+  ;; OPEN_WORLD:       (type $5 (func))
+
+  ;; OPEN_WORLD:      (type $configureAll (func (param (ref null $externs) (ref null $funcs) (ref null $bytes) externref)))
+  (type $configureAll (func (param (ref null $externs)) (param (ref null $funcs)) (param (ref null $bytes)) (param externref)))
+
+  (type $struct (struct))
+
+  (rec
+    ;; CHECK:      (type $7 (func (result i32)))
+
+    ;; CHECK:      (rec
+    ;; CHECK-NEXT:  (type $ret-any-1 (func (result anyref)))
+    ;; OPEN_WORLD:      (type $7 (func (result i32)))
+
+    ;; OPEN_WORLD:      (rec
+    ;; OPEN_WORLD-NEXT:  (type $ret-any-1 (func (result anyref)))
+    (type $ret-any-1 (func (result anyref)))
+
+    ;; use brands to allow $ret-any-1/2 to be optimized separately.
+    ;; CHECK:       (type $brand1 (struct))
+    ;; OPEN_WORLD:       (type $brand1 (struct))
+    (type $brand1 (struct))
+  )
+
+  (rec
+    (type $ret-any-2 (func (result anyref)))
+
+    (type $brand2 (struct))
+    (type $brand3 (struct))
+  )
+
+  ;; CHECK:      (import "wasm:js-prototypes" "configureAll" (func $configureAll (type $configureAll) (param (ref null $externs) (ref null $funcs) (ref null $bytes) externref)))
+  ;; OPEN_WORLD:      (import "wasm:js-prototypes" "configureAll" (func $configureAll (type $configureAll) (param (ref null $externs) (ref null $funcs) (ref null $bytes) externref)))
+  (import "wasm:js-prototypes" "configureAll" (func $configureAll (type $configureAll)))
+
+  ;; CHECK:      (data $bytes "12345678")
+
+  ;; CHECK:      (elem $externs externref (item (ref.null noextern)))
+  ;; OPEN_WORLD:      (data $bytes "12345678")
+
+  ;; OPEN_WORLD:      (elem $externs externref (item (ref.null noextern)))
+  (elem $externs externref
+    (ref.null extern)
+  )
+
+  ;; CHECK:      (elem $funcs func $foo $bar)
+  ;; OPEN_WORLD:      (elem $funcs func $foo $bar)
+  (elem $funcs funcref
+    (ref.func $foo)
+    (ref.func $bar)
+  )
+
+  (data $bytes "12345678")
+
+  ;; CHECK:      (start $start)
+  ;; OPEN_WORLD:      (start $start)
+  (start $start)
+
+  ;; CHECK:      (func $start (type $5)
+  ;; CHECK-NEXT:  (call $configureAll
+  ;; CHECK-NEXT:   (array.new_elem $externs $externs
+  ;; CHECK-NEXT:    (i32.const 0)
+  ;; CHECK-NEXT:    (i32.const 1)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (array.new_elem $funcs $funcs
+  ;; CHECK-NEXT:    (i32.const 0)
+  ;; CHECK-NEXT:    (i32.const 2)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (array.new_data $bytes $bytes
+  ;; CHECK-NEXT:    (i32.const 0)
+  ;; CHECK-NEXT:    (i32.const 8)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:   (ref.null noextern)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  ;; OPEN_WORLD:      (func $start (type $5)
+  ;; OPEN_WORLD-NEXT:  (call $configureAll
+  ;; OPEN_WORLD-NEXT:   (array.new_elem $externs $externs
+  ;; OPEN_WORLD-NEXT:    (i32.const 0)
+  ;; OPEN_WORLD-NEXT:    (i32.const 1)
+  ;; OPEN_WORLD-NEXT:   )
+  ;; OPEN_WORLD-NEXT:   (array.new_elem $funcs $funcs
+  ;; OPEN_WORLD-NEXT:    (i32.const 0)
+  ;; OPEN_WORLD-NEXT:    (i32.const 2)
+  ;; OPEN_WORLD-NEXT:   )
+  ;; OPEN_WORLD-NEXT:   (array.new_data $bytes $bytes
+  ;; OPEN_WORLD-NEXT:    (i32.const 0)
+  ;; OPEN_WORLD-NEXT:    (i32.const 8)
+  ;; OPEN_WORLD-NEXT:   )
+  ;; OPEN_WORLD-NEXT:   (ref.null noextern)
+  ;; OPEN_WORLD-NEXT:  )
+  ;; OPEN_WORLD-NEXT: )
+  (func $start
+    (call $configureAll
+      (array.new_elem $externs $externs
+        (i32.const 0) (i32.const 1))
+      (array.new_elem $funcs $funcs
+        (i32.const 0) (i32.const 2))
+      (array.new_data $bytes $bytes
+        (i32.const 0) (i32.const 8))
+      (ref.null extern)
+    )
+  )
+
+  ;; CHECK:      (func $foo (type $7) (result i32)
+  ;; CHECK-NEXT:  (i32.const 42)
+  ;; CHECK-NEXT: )
+  ;; OPEN_WORLD:      (func $foo (type $7) (result i32)
+  ;; OPEN_WORLD-NEXT:  (i32.const 42)
+  ;; OPEN_WORLD-NEXT: )
+  (func $foo (result i32)
+    ;; Nothing to do here anyhow, but do not error.
+    (i32.const 42)
+  )
+
+  ;; CHECK:      (func $bar (type $ret-any-1) (result anyref)
+  ;; CHECK-NEXT:  (struct.new_default $struct)
+  ;; CHECK-NEXT: )
+  ;; OPEN_WORLD:      (func $bar (type $ret-any-1) (result anyref)
+  ;; OPEN_WORLD-NEXT:  (struct.new_default $struct)
+  ;; OPEN_WORLD-NEXT: )
+  (func $bar (type $ret-any-1) (result anyref)
+    ;; This will not be refined due to configureAll.
+    (struct.new $struct)
+  )
+
+  ;; CHECK:      (func $unconfigured (type $ret-any-2) (result (ref (exact $struct)))
+  ;; CHECK-NEXT:  (struct.new_default $struct)
+  ;; CHECK-NEXT: )
+  ;; OPEN_WORLD:      (func $unconfigured (type $ret-any-2) (result (ref (exact $struct)))
+  ;; OPEN_WORLD-NEXT:  (struct.new_default $struct)
+  ;; OPEN_WORLD-NEXT: )
+  (func $unconfigured (type $ret-any-2) (result anyref)
+    ;; This is not referred to by configureAll, and can be refined.
+    (struct.new $struct)
+  )
+)
diff --git a/test/lit/passes/signature-refining.wast b/test/lit/passes/signature-refining.wast
index 1f1b3f3d47d..1533092e831 100644
--- a/test/lit/passes/signature-refining.wast
+++ b/test/lit/passes/signature-refining.wast
@@ -516,7 +516,7 @@
     ;; Also a single function, but no refinement is possible.
     (type $sig-cannot-refine (sub (func (result (ref func)))))
 
-  ;; The single function never returns, so no refinement is possible.
+    ;; The single function never returns, so no refinement is possible.
     (type $sig-unreachable (sub (func (result anyref))))
   )