Merge pull request #5031 from eeckstein/fix-linker-error-3.0

Always ensure that we generate code for referenced transparent functions.

Author: tkremenek

lib/SILOptimizer/IPO/DeadFunctionElimination.cpp

@@ -468,6 +468,30 @@ class ExternalFunctionDefinitionsElimination : FunctionLivenessComputation {
     /// Therefore there is no need for a liveness computation.
     /// The next line can be just replaced by:
     /// return false;
+
+    // Keep all transparent functions alive. This is important because we have
+    // to generate code for transparent functions.
+    // Here we handle the special case if a transparent function is referenced
+    // from a non-externally-available function (i.e. a function for which we
+    // generate code). And those function is only reachable through a
+    // vtable/witness-table. In such a case we would not visit the transparent
+    // function in findAliveFunctions() because we don't consider vtables/
+    // witness-tables as anchors.
+    for (SILFunction &F : *Module) {
+      if (isAvailableExternally(F.getLinkage()))
+        continue;
+
+      for (SILBasicBlock &BB : F) {
+        for (SILInstruction &I : BB) {
+          if (auto *FRI = dyn_cast<FunctionRefInst>(&I)) {
+            SILFunction *RefF = FRI->getReferencedFunction();
+            if (RefF->isTransparent() && RefF->isFragile())
+              ensureAlive(RefF);
+          }
+        }
+      }
+    }
+
     return FunctionLivenessComputation::findAliveFunctions();
   }
 

test/SILOptimizer/no_external_def_to_decl_for_transparent.sil

@@ -0,0 +1,39 @@
+// RUN: %target-sil-opt -enable-sil-verify-all %s -external-func-definition-elim | %FileCheck %s 
+
+sil_stage canonical
+
+import Builtin
+import Swift
+import SwiftShims
+
+
+public class X {
+  func testit() -> () -> ()
+  deinit
+  init()
+}
+
+// Check if we keep the body of the externally available transparent function.
+
+// CHECK-LABEL: sil public_external [transparent] [fragile] @imported_transparent_func : $@convention(thin) () -> () {
+sil public_external [transparent] [fragile] @imported_transparent_func : $@convention(thin) () -> () {
+bb0:
+  %r = tuple ()
+  return %r : $()
+}
+
+
+sil private @_TFC4test1X6testitfT_FT_T_  : $@convention(method) (@guaranteed X) -> @owned @callee_owned () -> () {
+bb0(%0 : $X):
+  %6 = function_ref @imported_transparent_func : $@convention(thin) () -> ()
+  %7 = thin_to_thick_function %6 : $@convention(thin) () -> () to $@callee_owned () -> ()
+  return %7 : $@callee_owned () -> ()
+}
+
+sil @_TFC4test1XD : $@convention(method) (@owned X) -> ()
+
+sil_vtable X {
+  #X.testit!1: _TFC4test1X6testitfT_FT_T_
+  #X.deinit!deallocator: _TFC4test1XD
+}
+