Swift Optimizer: add bridging for dynamic cast utilities

* `func canDynamicallyCast`
* `var CheckedCastAddrBranchInst.dynamicCastResult`

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/Utilities/OptUtils.swift

@@ -695,3 +695,23 @@ func getGlobalInitialization(
   }
   return nil
 }
+
+func canDynamicallyCast(from sourceType: Type, to destType: Type, in function: Function, sourceTypeIsExact: Bool) -> Bool? {
+  switch classifyDynamicCastBridged(sourceType.bridged, destType.bridged, function.bridged, sourceTypeIsExact) {
+    case .willSucceed: return true
+    case .maySucceed:  return nil
+    case .willFail:    return false
+    default: fatalError("unknown result from classifyDynamicCastBridged")
+  }
+}
+
+extension CheckedCastAddrBranchInst {
+  var dynamicCastResult: Bool? {
+    switch classifyDynamicCastBridged(bridged) {
+      case .willSucceed: return true
+      case .maySucceed:  return nil
+      case .willFail:    return false
+      default: fatalError("unknown result from classifyDynamicCastBridged")
+    }
+  }
+}

include/swift/SILOptimizer/OptimizerBridging.h

@@ -331,6 +331,18 @@ struct BridgedPassContext {
 
 bool FullApplySite_canInline(BridgedInstruction apply);
 
+enum class BridgedDynamicCastResult {
+  willSucceed,
+  maySucceed,
+  willFail
+};
+
+BridgedDynamicCastResult classifyDynamicCastBridged(BridgedType sourceTy, BridgedType destTy,
+                                                    BridgedFunction function,
+                                                    bool sourceTypeIsExact);
+
+BridgedDynamicCastResult classifyDynamicCastBridged(BridgedInstruction inst);
+
 //===----------------------------------------------------------------------===//
 //                          Pass registration
 //===----------------------------------------------------------------------===//

lib/SILOptimizer/PassManager/PassManager.cpp

@@ -18,6 +18,7 @@
 #include "swift/Demangling/Demangle.h"
 #include "../../IRGen/IRGenModule.h"
 #include "swift/SIL/ApplySite.h"
+#include "swift/SIL/DynamicCasts.h"
 #include "swift/SIL/SILCloner.h"
 #include "swift/SIL/SILFunction.h"
 #include "swift/SIL/SILModule.h"
@@ -1838,6 +1839,25 @@ bool FullApplySite_canInline(BridgedInstruction apply) {
       swift::FullApplySite(apply.unbridged()));
 }
 
+BridgedDynamicCastResult classifyDynamicCastBridged(BridgedType sourceTy, BridgedType destTy,
+                                                    BridgedFunction function,
+                                                    bool sourceTypeIsExact) {
+  static_assert((int)DynamicCastFeasibility::WillSucceed == (int)BridgedDynamicCastResult::willSucceed);
+  static_assert((int)DynamicCastFeasibility::MaySucceed  == (int)BridgedDynamicCastResult::maySucceed);
+  static_assert((int)DynamicCastFeasibility::WillFail    == (int)BridgedDynamicCastResult::willFail);
+
+  return static_cast<BridgedDynamicCastResult>(
+    classifyDynamicCast(function.getFunction()->getModule().getSwiftModule(),
+                        sourceTy.unbridged().getASTType(),
+                        destTy.unbridged().getASTType(),
+                        sourceTypeIsExact));
+}
+
+BridgedDynamicCastResult classifyDynamicCastBridged(BridgedInstruction inst) {
+  SILDynamicCastInst castInst(inst.unbridged());
+  return static_cast<BridgedDynamicCastResult>(castInst.classifyFeasibility(/*allowWholeModule=*/ false));
+}
+
 // TODO: can't be inlined to work around https://github.com/apple/swift/issues/64502
 BridgedCalleeAnalysis::CalleeList BridgedCalleeAnalysis::getCallees(BridgedValue callee) const {
   return ca->getCalleeListOfValue(callee.getSILValue());