[Distributed] SILOpt: Make sure that ad-hoc function does not get eliminated as unused

Author: xedin

lib/SILOptimizer/Analysis/CallerAnalysis.cpp

@@ -33,8 +33,10 @@ CallerAnalysis::FunctionInfo::FunctionInfo(SILFunction *f)
     : callerStates(),
       // TODO: Make this more aggressive by considering
       // final/visibility/etc.
-      mayHaveIndirectCallers(f->getDynamicallyReplacedFunction() ||
-                             canBeCalledIndirectly(f->getRepresentation())),
+      mayHaveIndirectCallers(
+          f->getDynamicallyReplacedFunction() ||
+          f->getReferencedAdHocRequirementWitnessFunction() ||
+          canBeCalledIndirectly(f->getRepresentation())),
       mayHaveExternalCallers(f->isPossiblyUsedExternally() ||
                              f->isAvailableExternally()) {}
 

lib/SILOptimizer/FunctionSignatureTransforms/FunctionSignatureOpts.cpp

@@ -646,6 +646,7 @@ bool FunctionSignatureTransform::run(bool hasCaller) {
   hasCaller |= FSOOptimizeIfNotCalled;
 
   if (!hasCaller && (F->getDynamicallyReplacedFunction() ||
+                     F->getReferencedAdHocRequirementWitnessFunction() ||
                      canBeCalledIndirectly(F->getRepresentation()))) {
     LLVM_DEBUG(llvm::dbgs() << "  function has no caller -> abort\n");
     return false;

lib/SILOptimizer/IPO/DeadFunctionElimination.cpp

@@ -101,6 +101,9 @@ class DeadFunctionAndGlobalElimination {
     if (F->isDynamicallyReplaceable())
       return true;
 
+    if (F->getReferencedAdHocRequirementWitnessFunction())
+      return true;
+
     // Don't remove pre-specialized functions. We need to preserver the
     // pre-specialization specifications from other modules.
     if (F->hasPrespecialization())
@@ -325,6 +328,9 @@ class DeadFunctionAndGlobalElimination {
 
     LLVM_DEBUG(llvm::dbgs() << "    scan function " << F->getName() << '\n');
 
+    if (auto *adHocWitness = F->getReferencedAdHocRequirementWitnessFunction())
+      ensureAlive(adHocWitness);
+
     // First scan all instructions of the function.
     for (SILBasicBlock &BB : *F) {
       for (SILInstruction &I : BB) {