Add SILParser support for [dynamically_replaceable].

Author: atrick

include/swift/AST/DiagnosticsParse.def

@@ -731,6 +731,8 @@ ERROR(expected_type_after_arrow,none,
 ERROR(function_type_argument_label,none,
       "function types cannot have argument labels; use '_' before %0",
       (Identifier))
+ERROR(expected_dynamic_func_attr,none,
+      "expected a dynamically_replaceable function", ())
 
 // Enum Types
 ERROR(expected_expr_enum_case_raw_value,PointsToFirstBadToken,

include/swift/SIL/SILFunction.h

@@ -590,7 +590,6 @@ class SILFunction
     return IsDynamicallyReplaceable_t(IsDynamicReplaceable);
   }
   void setIsDynamic(IsDynamicallyReplaceable_t value = IsDynamic) {
-    assert(IsDynamicReplaceable == IsNotDynamic && "already set");
     IsDynamicReplaceable = value;
     assert(!Transparent || !IsDynamicReplaceable);
   }

lib/ParseSIL/ParseSIL.cpp

@@ -2722,6 +2722,14 @@ bool SILParser::parseSILInstruction(SILBuilder &B) {
     if (parseSILFunctionRef(InstLoc, Fn) ||
         parseSILDebugLocation(InstLoc, B))
       return true;
+    // Set a forward reference's dynamic property for the first time.
+    if (!Fn->isDynamicallyReplaceable()) {
+      if (!Fn->empty()) {
+        P.diagnose(P.Tok, diag::expected_dynamic_func_attr);
+        return true;
+      }
+      Fn->setIsDynamic();
+    }
     ResultVal = B.createDynamicFunctionRef(InstLoc, Fn);
     break;
   }