Improve TypeLayout IRGen for Fixed Structs

If the Aligned Group is fixed sized and alignment, rather than doing an
alignment computation at runtime, we compute the offset for each field
and emit a GEP.

Author: Gwen Mittertreiner

lib/IRGen/GenStruct.cpp

@@ -708,7 +708,7 @@ namespace {
         return fields[0];
       }
 
-      return IGM.typeLayoutCache.getOrCreateAlignedGroupEntry(fields, 1, false);
+      return IGM.typeLayoutCache.getOrCreateAlignedGroupEntry(fields, 1);
     }
 
     // We have an indirect schema.

lib/IRGen/GenTuple.cpp

@@ -329,10 +329,9 @@ namespace {
         return fields[0];
       }
 
-      return IGM.typeLayoutCache.getOrCreateAlignedGroupEntry(fields, 1, false);
+      return IGM.typeLayoutCache.getOrCreateAlignedGroupEntry(fields, 1);
     }
 
-
     llvm::Value *getEnumTagSinglePayload(IRGenFunction &IGF,
                                          llvm::Value *numEmptyCases,
                                          Address structAddr,