[NFC] SIL: Added SILInstructionContext.

It has a module or maybe a function.  In the future we may want to
change this to be either a SILFunction or a SILGlobalVariable.

Author: nate-chandler

include/swift/SIL/SILInstruction.h

@@ -31,6 +31,7 @@
 #include "swift/Basic/OptionSet.h"
 #include "swift/Basic/ProfileCounter.h"
 #include "swift/Basic/Range.h"
+#include "swift/Basic/TaggedUnion.h"
 #include "swift/SIL/Consumption.h"
 #include "swift/SIL/SILAllocated.h"
 #include "swift/SIL/SILArgumentArrayRef.h"
@@ -4150,6 +4151,24 @@ class KeyPathInst final
   ~KeyPathInst();
 };
 
+struct SILInstructionContext {
+  using Storage = TaggedUnion<SILModule *, SILFunction *>;
+  Storage storage;
+
+  static SILInstructionContext forModule(SILModule &M) { return {Storage(&M)}; }
+
+  static SILInstructionContext forFunction(SILFunction &F) {
+    return {Storage(&F)};
+  }
+
+  static SILInstructionContext forFunctionInModule(SILFunction *F,
+                                                   SILModule &M);
+
+  SILFunction *getFunction();
+
+  SILModule &getModule();
+};
+
 /// Represents an invocation of builtin functionality provided by the code
 /// generator.
 class BuiltinInst final

lib/SIL/IR/SILInstruction.cpp

@@ -1974,6 +1974,26 @@ UncheckedTakeEnumDataAddrInst::isDestructive(EnumDecl *forEnum, SILModule &M) {
   return false;
 }
 
+SILInstructionContext SILInstructionContext::forFunctionInModule(SILFunction *F,
+                                                                 SILModule &M) {
+  if (F) {
+    assert(&F->getModule() == &M);
+    return forFunction(*F);
+  }
+  return forModule(M);
+}
+
+SILFunction *SILInstructionContext::getFunction() {
+  return *storage.dyn_cast<SILFunction *>();
+}
+
+SILModule &SILInstructionContext::getModule() {
+  if (auto *m = storage.dyn_cast<SILModule *>()) {
+    return **m;
+  }
+  return storage.get<SILFunction *>()->getModule();
+}
+
 #ifndef NDEBUG
 
 //---