Use the file name from linemarker for debug info if an input is preprocessed source.

[twoh]

Summary

Even in the case of the input file is a preprocessed source, clang uses the file name of the preprocesses source for debug info (DW_AT_name attribute for DW_TAG_compile_unit). However, gcc uses the file name specified in the first linemarker instead. This makes more sense because the one specified in the linemarker represents the "actual" source file name.

Clang already uses the file name specified in the first linemarker for Module name (https://github.com/llvm-mirror/clang/blob/master/lib/Frontend/FrontendAction.cpp#L779) if the input is preprocessed. This patch makes clang to use the same value for debug info as well.

[twoh]

Relocate.

[dblaikie]

Looks plausible (not sure how nice it is to use the llvm::Module itself to communicate the file name to this bit of logic - I'll leave that to Richard Smith to judge, I think)

test/CodeGen/debug-info-preprocessed-file.i

10

Should probably be a bit more specific in the check - verifying that the DICompileUnit's DIFile is the one you're checking here. (not that there's any other DI* that would have a DIFile here, but still)

[twoh]

Addressing dblaikie's comments. Thanks!

[twoh]

Ping. Thanks!

[rnk]

lgtm

lib/CodeGen/CGDebugInfo.cpp

 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/Version.h"
 #include "clang/Frontend/CodeGenOptions.h"
+#include "clang/Frontend/FrontendOptions.h"
 #include "clang/Lex/HeaderSearchOptions.h"
 #include "clang/Lex/ModuleMap.h"
 #include "clang/Lex/PreprocessorOptions.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
void CGDebugInfo::CreateCompileUnit() {
   std::string MainFileDir;
   if (const FileEntry *MainFile = SM.getFileEntryForID(SM.getMainFileID())) {
     MainFileDir = remapDIPath(MainFile->getDir()->getName());
     if (MainFileDir != ".") {
       llvm::SmallString<1024> MainFileDirSS(MainFileDir);
       llvm::sys::path::append(MainFileDirSS, MainFileName);
       MainFileName = MainFileDirSS.str();
     }
+    // If the main file name provided is identical to the input file name, and
+    // if the input file is a preprocessed source, use the module name for
+    // debug info. The module name comes from the name specified in the first
+    // linemarker if the input is a preprocessed source.
+    if (MainFile->getName() == MainFileName &&
+        FrontendOptions::getInputKindForExtension(
+            MainFile->getName().rsplit('.').second)
+            .isPreprocessed())
+      MainFileName = CGM.getModule().getName().str();
+
     CSKind = computeChecksum(SM.getMainFileID(), Checksum);
   }
 
   llvm::dwarf::SourceLanguage LangTag;
   const LangOptions &LO = CGM.getLangOpts();
   if (LO.CPlusPlus) {
     if (LO.ObjC1)
       LangTag = llvm::dwarf::DW_LANG_ObjC_plus_plus;

test/CodeGen/debug-info-preprocessed-file.i

+# 1 "/foo/bar/preprocessed-input.c"
+# 1 "<built-in>" 1
+# 1 "<built-in>" 3
+# 318 "<built-in>" 3
+# 1 "<command line>" 1
+# 1 "<built-in>" 2
+# 1 "preprocessed-input.c" 2
+
+// RUN: %clang -g -c -S -emit-llvm -o - %s | FileCheck %s
+// CHECK: !DIFile(filename: "/foo/bar/preprocessed-input.c"