[clang] Add cc1 option for dumping layout for all complete types

This change adds an option which, in addition to dumping the record
layout as is done by -fdump-record-layouts, causes us to compute the
layout for all complete record types (rather than the as-needed basis
which is usually done by clang), so that we will dump them as well.
This is useful if we are looking for layout differences across large
code bases without needing to instantiate every type we are interested in.

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D104484

clang/include/clang/Basic/LangOptions.def

@@ -265,6 +265,7 @@ BENIGN_LANGOPT(ModulesDebugInfo , 1, 0, "Modules debug info")
 BENIGN_LANGOPT(ElideConstructors , 1, 1, "C++ copy constructor elision")
 BENIGN_LANGOPT(DumpRecordLayouts , 1, 0, "dumping the layout of IRgen'd records")
 BENIGN_LANGOPT(DumpRecordLayoutsSimple , 1, 0, "dumping the layout of IRgen'd records in a simple form")
+BENIGN_LANGOPT(DumpRecordLayoutsComplete , 1, 0, "dumping the AST layout of all complete records")
 BENIGN_LANGOPT(DumpVTableLayouts , 1, 0, "dumping the layouts of emitted vtables")
 LANGOPT(NoConstantCFStrings , 1, 0, "no constant CoreFoundation strings")
 BENIGN_LANGOPT(InlineVisibilityHidden , 1, 0, "hidden visibility for inline C++ methods")

clang/include/clang/Driver/Options.td

@@ -5381,10 +5381,13 @@ def stats_file : Joined<["-"], "stats-file=">,
 def fdump_record_layouts_simple : Flag<["-"], "fdump-record-layouts-simple">,
   HelpText<"Dump record layout information in a simple form used for testing">,
   MarshallingInfoFlag<LangOpts<"DumpRecordLayoutsSimple">>;
+def fdump_record_layouts_complete : Flag<["-"], "fdump-record-layouts-complete">,
+  HelpText<"Dump record layout information for all complete types">,
+  MarshallingInfoFlag<LangOpts<"DumpRecordLayoutsComplete">>;
 def fdump_record_layouts : Flag<["-"], "fdump-record-layouts">,
   HelpText<"Dump record layout information">,
   MarshallingInfoFlag<LangOpts<"DumpRecordLayouts">>,
-  ImpliedByAnyOf<[fdump_record_layouts_simple.KeyPath]>;
+  ImpliedByAnyOf<[fdump_record_layouts_simple.KeyPath, fdump_record_layouts_complete.KeyPath]>;
 def fix_what_you_can : Flag<["-"], "fix-what-you-can">,
   HelpText<"Apply fix-it advice even in the presence of unfixable errors">,
   MarshallingInfoFlag<FrontendOpts<"FixWhatYouCan">>;

clang/lib/AST/Decl.cpp

@@ -4581,6 +4581,13 @@ RecordDecl::field_iterator RecordDecl::field_begin() const {
 void RecordDecl::completeDefinition() {
   assert(!isCompleteDefinition() && "Cannot redefine record!");
   TagDecl::completeDefinition();
+
+  ASTContext &Ctx = getASTContext();
+
+  // Layouts are dumped when computed, so if we are dumping for all complete
+  // types, we need to force usage to get types that wouldn't be used elsewhere.
+  if (Ctx.getLangOpts().DumpRecordLayoutsComplete)
+    (void)Ctx.getASTRecordLayout(this);
 }
 
 /// isMsStruct - Get whether or not this record uses ms_struct layout.

clang/test/Layout/dump-complete.cpp

@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -emit-llvm-only -fdump-record-layouts-complete %s | FileCheck %s
+
+struct a {
+  int x;
+};
+
+struct b {
+  char y;
+} foo;
+
+class c {};
+
+class d;
+
+// CHECK:          0 | struct a
+// CHECK:          0 | struct b
+// CHECK:          0 | class c
+// CHECK-NOT:      0 | class d