SignatureRefining: Do not refine types of imported functions (#4727)

Spec and VM support for that is not yet stable (atm VMs do not allow complex user-
defined types to be passed around).

2 files changed, 34 insertions, 0 deletions

diff --git a/src/passes/SignatureRefining.cpp b/src/passes/SignatureRefining.cpp
index bde1c4fb9..0574df434 100644
--- a/src/passes/SignatureRefining.cpp
+++ b/src/passes/SignatureRefining.cpp
@@ -81,6 +81,10 @@ struct SignatureRefining : public Pass {
     ModuleUtils::ParallelFunctionAnalysis<Info, Mutable> analysis(
       *module, [&](Function* func, Info& info) {
         if (func->imported()) {
+          // Avoid changing the types of imported functions. Spec and VM support
+          // for that is not yet stable.
+          // TODO: optimize this when possible in the future
+          info.canModify = false;
           return;
         }
         info.calls = std::move(FindAll<Call>(func->body).list);
@@ -111,6 +115,11 @@ struct SignatureRefining : public Pass {
       // Add the function's return LUB to the one for the heap type of that
       // function.
       allInfo[func->type].resultsLUB.combine(info.resultsLUB);
+
+      // If one function cannot be modified, that entire type cannot be.
+      if (!info.canModify) {
+        allInfo[func->type].canModify = false;
+      }
     }
 
     // We cannot alter the signature of an exported function, as the outside may
diff --git a/test/lit/passes/signature-refining.wast b/test/lit/passes/signature-refining.wast
index 8e5d3b75e..02041c91c 100644
--- a/test/lit/passes/signature-refining.wast
+++ b/test/lit/passes/signature-refining.wast
@@ -720,3 +720,28 @@
     )
   )
 )
+
+;; Do not modify the types used on imported functions (until the spec and VM
+;; support becomes stable).
+(module
+  ;; CHECK:      (type $ref?|data|_=>_none (func_subtype (param (ref null data)) func))
+
+  ;; CHECK:      (type $none_=>_none (func_subtype func))
+
+  ;; CHECK:      (type $struct (struct_subtype  data))
+  (type $struct (struct_subtype data))
+
+  ;; CHECK:      (import "a" "b" (func $import (param (ref null data))))
+  (import "a" "b" (func $import (param (ref null data))))
+
+  ;; CHECK:      (func $test (type $none_=>_none)
+  ;; CHECK-NEXT:  (call $import
+  ;; CHECK-NEXT:   (struct.new_default $struct)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $test
+    (call $import
+      (struct.new $struct)
+    )
+  )
+)