[SILOpt] Make lex-lt options optional.

Use boolOrDefault to distinguish betweeen options that are unset and
those that are set (to some value).  Then, only override the default
values in SILOptions when the options are specified.

Author: nate-chandler

tools/sil-opt/SILOpt.cpp

@@ -58,6 +58,18 @@ enum class OptGroup {
   Lowering
 };
 
+Optional<bool> toOptionalBool(llvm::cl::boolOrDefault defaultable) {
+  switch (defaultable) {
+  case llvm::cl::BOU_TRUE:
+    return true;
+  case llvm::cl::BOU_FALSE:
+    return false;
+  case llvm::cl::BOU_UNSET:
+    return None;
+  }
+  llvm_unreachable("Bad case for llvm::cl::boolOrDefault!");
+}
+
 } // end anonymous namespace
 
 static llvm::cl::opt<std::string>
@@ -105,20 +117,20 @@ static llvm::cl::opt<bool>
 EnableExperimentalConcurrency("enable-experimental-concurrency",
                    llvm::cl::desc("Enable experimental concurrency model."));
 
-static llvm::cl::opt<bool> EnableLexicalLifetimes(
-    "enable-lexical-lifetimes", llvm::cl::init(false),
+static llvm::cl::opt<llvm::cl::boolOrDefault> EnableLexicalLifetimes(
+    "enable-lexical-lifetimes", llvm::cl::init(llvm::cl::BOU_UNSET),
     llvm::cl::desc("Enable lexical lifetimes. Mutually exclusive with "
                    "enable-lexical-borrow-scopes and "
                    "disable-lexical-lifetimes."));
 
-static llvm::cl::opt<bool>
+static llvm::cl::opt<llvm::cl::boolOrDefault>
     EnableLexicalBorrowScopes("enable-lexical-borrow-scopes",
-                              llvm::cl::init(true),
+                              llvm::cl::init(llvm::cl::BOU_UNSET),
                               llvm::cl::desc("Enable lexical borrow scopes."));
 
-static llvm::cl::opt<bool>
-EnableExperimentalMoveOnly("enable-experimental-move-only",
-                   llvm::cl::desc("Enable experimental distributed actors."));
+static llvm::cl::opt<llvm::cl::boolOrDefault> EnableExperimentalMoveOnly(
+    "enable-experimental-move-only", llvm::cl::init(llvm::cl::BOU_UNSET),
+    llvm::cl::desc("Enable experimental distributed actors."));
 
 static llvm::cl::opt<bool>
 EnableExperimentalDistributed("enable-experimental-distributed",
@@ -520,8 +532,11 @@ int main(int argc, char **argv) {
     EnableExperimentalConcurrency;
   Invocation.getLangOptions().EnableExperimentalDistributed =
     EnableExperimentalDistributed;
-  Invocation.getLangOptions().EnableExperimentalMoveOnly =
-    EnableExperimentalMoveOnly;
+  Optional<bool> enableExperimentalMoveOnly =
+      toOptionalBool(EnableExperimentalMoveOnly);
+  if (enableExperimentalMoveOnly)
+    Invocation.getLangOptions().EnableExperimentalMoveOnly =
+        *enableExperimentalMoveOnly;
 
   Invocation.getLangOptions().EnableObjCInterop =
     EnableObjCInterop ? true :
@@ -623,22 +638,34 @@ int main(int argc, char **argv) {
   if (SILOpts.CopyPropagation == CopyPropagationOption::Off)
     SILOpts.LexicalLifetimes = LexicalLifetimesOption::DiagnosticMarkersOnly;
 
+  Optional<bool> enableLexicalLifetimes =
+      toOptionalBool(EnableLexicalLifetimes);
+  Optional<bool> enableLexicalBorrowScopes =
+      toOptionalBool(EnableLexicalBorrowScopes);
+
   // Enable lexical lifetimes if it is set or if experimental move only is
   // enabled. This is because move only depends on lexical lifetimes being
   // enabled and it saved some typing ; ).
-  bool enableLexicalLifetimes =
-      EnableLexicalLifetimes | EnableExperimentalMoveOnly;
-  if (enableLexicalLifetimes && !EnableLexicalBorrowScopes) {
+  bool specifiedLexicalLifetimesEnabled =
+      enableExperimentalMoveOnly && *enableExperimentalMoveOnly &&
+      enableLexicalLifetimes && *enableLexicalLifetimes;
+  if (specifiedLexicalLifetimesEnabled && enableLexicalBorrowScopes &&
+      !*enableLexicalBorrowScopes) {
     fprintf(
         stderr,
         "Error! Cannot specify both -enable-lexical-borrow-scopes=false and "
         "either -enable-lexical-lifetimes or -enable-experimental-move-only.");
     exit(-1);
   }
   if (enableLexicalLifetimes)
-    SILOpts.LexicalLifetimes = LexicalLifetimesOption::On;
-  if (!EnableLexicalBorrowScopes)
-    SILOpts.LexicalLifetimes = LexicalLifetimesOption::Off;
+    SILOpts.LexicalLifetimes =
+        *enableLexicalLifetimes ? LexicalLifetimesOption::On
+                                : LexicalLifetimesOption::DiagnosticMarkersOnly;
+  if (enableLexicalBorrowScopes)
+    SILOpts.LexicalLifetimes =
+        *enableLexicalBorrowScopes
+            ? LexicalLifetimesOption::DiagnosticMarkersOnly
+            : LexicalLifetimesOption::Off;
 
   serialization::ExtendedValidationInfo extendedInfo;
   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> FileBufOrErr =