Represent Clang macro definitions from -Xcc options in the debug info.

Currently -Xcc options are serialized in Swift modules, but they are
not saved as attributes to the DW_TAG_module representing the imported
clang module. This patch saves all *user-specified* -D macros there,
but it does not save any macros that are added by the ClangImporter
itself.

<rdar://problem/31990102>

include/swift/AST/IRGenOptions.h

@@ -76,6 +76,9 @@ public:
   /// The command line string that is to be stored in the DWARF debug info.
   std::string DWARFDebugFlags;
 
+  /// List of -Xcc -D macro definitions.
+  std::vector<std::string> ClangDefines;
+
   /// The libraries and frameworks specified on the command line.
   SmallVector<LinkLibrary, 4> LinkLibraries;
 

lib/Frontend/CompilerInvocation.cpp

@@ -1470,6 +1470,14 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
     }
   }
 
+  for (const Arg *A : make_range(Args.filtered_begin(OPT_Xcc),
+                                 Args.filtered_end())) {
+    StringRef Opt = A->getValue();
+    if (Opt.startswith("-D") || Opt.startswith("-U"))
+      Opts.ClangDefines.push_back(Opt);
+  }
+
+
   for (const Arg *A : make_range(Args.filtered_begin(OPT_l, OPT_framework),
                                  Args.filtered_end())) {
     LibraryKind Kind;

lib/IRGen/IRGenDebugInfo.cpp

@@ -93,6 +93,7 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
 
   llvm::BumpPtrAllocator DebugInfoNames;
   StringRef CWDName;                    /// The current working directory.
+  SmallString<0> ConfigMacros;          /// User-provided -D macro definitions.
   llvm::DICompileUnit *TheCU = nullptr; /// The current compilation unit.
   llvm::DIFile *MainFile = nullptr;     /// The main file.
   llvm::DIModule *MainModule = nullptr; /// The current module.
@@ -582,13 +583,13 @@ private:
   }
 
   llvm::DIModule *getOrCreateModule(StringRef Key, llvm::DIScope *Parent,
-                                    StringRef Name, StringRef IncludePath) {
+                                    StringRef Name, StringRef IncludePath,
+                                    StringRef ConfigMacros = StringRef()) {
     // Look in the cache first.
     auto Val = DIModuleCache.find(Key);
     if (Val != DIModuleCache.end())
       return cast<llvm::DIModule>(Val->second);
 
-    StringRef ConfigMacros;
     StringRef Sysroot = IGM.Context.SearchPathOpts.SDKPath;
     auto M =
         DBuilder.createModule(Parent, Name, ConfigMacros, IncludePath, Sysroot);
@@ -606,11 +607,12 @@ private:
         Parent = getOrCreateModule(PM);
       }
       return getOrCreateModule(ClangModule->getFullModuleName(), Parent,
-                               Desc.getModuleName(), Desc.getPath());
+                               Desc.getModuleName(), Desc.getPath(),
+                               ConfigMacros);
     }
     // Handle PCH.
     return getOrCreateModule(Desc.getASTFile(), nullptr, Desc.getModuleName(),
-                             Desc.getPath());
+                             Desc.getPath(), ConfigMacros);
   };
 
   TypeAliasDecl *getMetadataType() {
@@ -1534,6 +1536,24 @@ IRGenDebugInfoImpl::IRGenDebugInfoImpl(const IRGenOptions &Opts,
   MainModule =
       getOrCreateModule(Opts.ModuleName, TheCU, Opts.ModuleName, AbsMainFile);
   DBuilder.createImportedModule(MainFile, MainModule, 1);
+
+  // Macro definitions that were defined by the user with "-Xcc -D" on the
+  // command line. This does not include any macros defined by ClangImporter.
+  llvm::raw_svector_ostream OS(ConfigMacros);
+  unsigned I = 0;
+  // Translate the macro definitions back into a commmand line.
+  for (auto &Macro : Opts.ClangDefines) {
+    if (++I > 1)
+      OS << ' ';
+    OS << '"';
+    for (char c : Macro)
+      switch (c) {
+      case '\\': OS << "\\\\"; break;
+      case '"':  OS << "\\\""; break;
+      default: OS << c;
+      }
+    OS << '"';
+  }
 }
 
 void IRGenDebugInfoImpl::finalize() {

test/DebugInfo/ImportClangSubmodule.swift

@@ -1,4 +1,5 @@
-// RUN: %target-swift-frontend -emit-ir %s -g -I %S/Inputs -o - | %FileCheck %s
+// RUN: %target-swift-frontend -emit-ir %s -g -I %S/Inputs \
+// RUN:   -Xcc -DFOO="foo" -Xcc -UBAR -o - | %FileCheck %s
 
 // CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "Bar",
 // CHECK-SAME:             scope: ![[SUBMODULE:[0-9]+]]
@@ -6,6 +7,9 @@
 // CHECK: ![[SUBMODULE]] = !DIModule(scope: ![[CLANGMODULE:[0-9]+]],
 // CHECK-SAME:                       name: "SubModule",
 // CHECK: ![[CLANGMODULE]] = !DIModule(scope: null, name: "ClangModule",
+// CHECK-SAME:                         configMacros:
+// CHECK-SAME:                         {{..}}-DFOO=foo{{..}}
+// CHECK-SAME:                         {{..}}-UBAR{{..}}
 // CHECK: !DIImportedEntity({{.*}}, entity: ![[SUBMODULE]], line: [[@LINE+1]])
 import ClangModule.SubModule