[silgen] Add support for emitting guaranteed self behind the flag -enable-guaranteed-self.

This does not have any tests since I am going to start going through SILGen
tests and updating them for guaranteed self as the appropriate tests.

*NOTE* There is more work to be done in terms of thunks, but the basic
functionality is done.

rdar://15729033

Swift SVN r23653

include/swift/AST/SILOptions.h

@@ -88,6 +88,9 @@ public:
 
   /// Should we optimize function signatures. Disabled by default.
   bool EnableFuncSigOpts = true;
+
+  /// Should we emit self as a guaranteed parameter. Disabled by default.
+  bool EnableGuaranteedSelf = false;
 };
 
 } // end namespace swift

include/swift/Option/FrontendOptions.td

@@ -238,4 +238,7 @@ def disable_func_sig_opts : Flag<["-"], "disable-func-sig-opts">,
 
 def interpret : Flag<["-"], "interpret">, HelpText<"Immediate mode">, ModeOpt;
 
+def enable_guaranteed_self : Flag<["-"], "enable-guaranteed-self">,
+  HelpText<"Enable the passing of self as a guaranteed parameter">;
+
 } // end let Flags = [FrontendOption, NoDriverOption, HelpHidden]

lib/Frontend/CompilerInvocation.cpp

@@ -865,6 +865,7 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
   Opts.DebugSerialization |= Args.hasArg(OPT_sil_debug_serialization);
   Opts.PrintInstCounts |= Args.hasArg(OPT_print_inst_counts);
   Opts.EnableFuncSigOpts &= !Args.hasArg(OPT_disable_func_sig_opts);
+  Opts.EnableGuaranteedSelf |= Args.hasArg(OPT_enable_guaranteed_self);
 
   return false;
 }

lib/SIL/SILFunctionType.cpp

@@ -481,7 +481,11 @@ static CanSILFunctionType getSILFunctionType(SILModule &M,
 namespace {
   /// The default Swift conventions.
   struct DefaultConventions : Conventions {
-    DefaultConventions() : Conventions(ConventionsKind::Default) {}
+    bool hasGuaranteedSelf;
+
+    DefaultConventions(bool guaranteedSelf)
+      : Conventions(ConventionsKind::Default),
+        hasGuaranteedSelf(guaranteedSelf) {}
 
     ParameterConvention getIndirectParameter(unsigned index,
                                              CanType type) const override {
@@ -502,6 +506,8 @@ namespace {
     }
 
     ParameterConvention getDirectSelfParameter(CanType type) const override {
+      if (hasGuaranteedSelf)
+        return ParameterConvention::Direct_Guaranteed;
       return ParameterConvention::Direct_Owned;
     }
 
@@ -561,9 +567,11 @@ static CanSILFunctionType getNativeSILFunctionType(SILModule &M,
                               extInfo, DefaultBlockConventions());
 
   case AnyFunctionType::Representation::Thin:
-  case AnyFunctionType::Representation::Thick:
+  case AnyFunctionType::Representation::Thick: {
+    bool enableGuaranteedSelf = M.getOptions().EnableGuaranteedSelf;
     return getSILFunctionType(M, origType, substType, substInterfaceType,
-                              extInfo, DefaultConventions());
+                              extInfo, DefaultConventions(enableGuaranteedSelf));
+  }
   }
 }