SILCombine: We are not guaranteed to get a function_ref instruction here

Also fix an issue in that cast optimizer and objc bridging thunks that
are marked dynamic.

Same test case tests both issues.

rdar://51068786

Author: aschwaighofer

lib/SILOptimizer/SILCombiner/SILCombinerApplyVisitors.cpp

@@ -1362,7 +1362,11 @@ static bool knowHowToEmitReferenceCountInsts(ApplyInst *Call) {
   if (Call->getNumArguments() != 1)
     return false;
 
-  FunctionRefInst *FRI = cast<FunctionRefInst>(Call->getCallee());
+  // FIXME: We could handle dynamic_function_ref instructions here because the
+  // code only looks at the function type.
+  FunctionRefInst *FRI = dyn_cast<FunctionRefInst>(Call->getCallee());
+  if (!FRI)
+    return false;
   SILFunction *F = FRI->getReferencedFunction();
   auto FnTy = F->getLoweredFunctionType();
 

lib/SILOptimizer/Utils/CastOptimizer.cpp

@@ -271,7 +271,7 @@ CastOptimizer::optimizeBridgedObjCToSwiftCast(SILDynamicCastInst dynamicCast) {
   // Now emit the a cast from the casted ObjC object into a target type.
   // This is done by means of calling _forceBridgeFromObjectiveC or
   // _conditionallyBridgeFromObjectiveC_bridgeable from the Target type.
-  auto *funcRef = Builder.createFunctionRef(Loc, bridgingFunc);
+  auto *funcRef = Builder.createFunctionRefFor(Loc, bridgingFunc);
   SubstitutionMap subMap = lookupBridgeToObjCProtocolSubs(mod, target);
 
   auto MetaTy = MetatypeType::get(target, MetatypeRepresentation::Thick);
@@ -588,7 +588,7 @@ CastOptimizer::optimizeBridgedSwiftToObjCCast(SILDynamicCastInst dynamicCast) {
   }
 
   SILBuilderWithScope Builder(Inst, builderContext);
-  auto FnRef = Builder.createFunctionRef(Loc, bridgedFunc);
+  auto FnRef = Builder.createFunctionRefFor(Loc, bridgedFunc);
   auto ParamTypes = SubstFnTy.castTo<SILFunctionType>()->getParameters();
   if (Src->getType().isAddress() && !substConv.isSILIndirect(ParamTypes[0])) {
     // Create load

test/SILOptimizer/sil_combine_objc_bridge.sil

@@ -64,6 +64,23 @@ bb0(%0 : $AnNSArray):
   return %4 : $AnNSArray
 }
 
+sil [_semantics "convertFromObjectiveC"] [dynamically_replacable] @bridgeFromObjectiveC2 :
+  $@convention(thin) <τ_0_0> (@owned AnNSArray) -> @owned AnArray<τ_0_0>
+
+sil [_semantics "convertToObjectiveC"] [dynamically_replacable] @bridgeToObjectiveC2:
+  $@convention(method) <τ_0_0> (@owned AnArray<τ_0_0>) -> @owned AnNSArray
+
+// This should not crash.
+sil @bridge_from_to_owned_dynamic : $@convention(thin) (@owned AnNSArray) -> @owned AnNSArray {
+bb0(%0 : $AnNSArray):
+  %1 = dynamic_function_ref @bridgeFromObjectiveC2 : $@convention(thin) <AnyObject> (@owned AnNSArray) -> @owned AnArray<AnyObject>
+  %2 = apply %1<AnyObject>(%0) : $@convention(thin) <AnyObject> (@owned AnNSArray) -> @owned AnArray<AnyObject>
+  retain_value %2 : $AnArray<AnyObject>
+  release_value %2 : $AnArray<AnyObject>
+  %3 = dynamic_function_ref @bridgeToObjectiveC2 : $@convention(method) <AnyObject> (@owned AnArray<AnyObject>) -> @owned AnNSArray
+  %4 = apply %3<AnyObject>(%2) : $@convention(method) <AnyObject> (@owned AnArray<AnyObject>) -> @owned AnNSArray
+  return %4 : $AnNSArray
+}
 // CHECK-LABEL: sil @bridge_to_from_owned
 // CHECK-NOT: apply
 // CHECK: retain_value