Revert "Avoid emitting redundant or unusable directories in DIFile metadata entries."

This reverts commit r348154 and follow-up commits r348211 and r3248213.
Reason: the original commit broke compiler-rt tests and a follow-up fix
(r348203) broke our integrate and was reverted.

llvm-svn: 348280
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index c556996..3492fba 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -181,7 +181,8 @@
   SourceManager &SM = CGM.getContext().getSourceManager();
   auto *Scope = cast<llvm::DIScope>(LexicalBlockStack.back());
   PresumedLoc PCLoc = SM.getPresumedLoc(CurLoc);
-  if (PCLoc.isInvalid() || Scope->getFile() == getOrCreateFile(CurLoc))
+
+  if (PCLoc.isInvalid() || Scope->getFilename() == PCLoc.getFilename())
     return;
 
   if (auto *LBF = dyn_cast<llvm::DILexicalBlockFile>(Scope)) {
@@ -409,13 +410,13 @@
   SourceManager &SM = CGM.getContext().getSourceManager();
   PresumedLoc PLoc = SM.getPresumedLoc(Loc);
 
-  StringRef FileName = PLoc.getFilename();
-  if (PLoc.isInvalid() || FileName.empty())
+  if (PLoc.isInvalid() || StringRef(PLoc.getFilename()).empty())
     // If the location is not valid then use main input file.
     return getOrCreateMainFile();
 
   // Cache the results.
-  auto It = DIFileCache.find(FileName.data());
+  const char *fname = PLoc.getFilename();
+  auto It = DIFileCache.find(fname);
 
   if (It != DIFileCache.end()) {
     // Verify that the information still exists.
@@ -430,41 +431,11 @@
   if (CSKind)
     CSInfo.emplace(*CSKind, Checksum);
 
-  StringRef Dir;
-  StringRef File;
-  std::string RemappedFile = remapDIPath(FileName);
-  std::string CurDir = remapDIPath(getCurrentDirname());
-  SmallString<128> DirBuf;
-  SmallString<128> FileBuf;
-  if (llvm::sys::path::is_absolute(RemappedFile)) {
-    // Strip the common prefix (if it is more than just "/") from current
-    // directory and FileName for a more space-efficient encoding.
-    auto FileIt = llvm::sys::path::begin(RemappedFile);
-    auto FileE = llvm::sys::path::end(RemappedFile);
-    auto CurDirIt = llvm::sys::path::begin(CurDir);
-    auto CurDirE = llvm::sys::path::end(CurDir);
-    for (; CurDirIt != CurDirE && *CurDirIt == *FileIt; ++CurDirIt, ++FileIt)
-      llvm::sys::path::append(DirBuf, *CurDirIt);
-    if (std::distance(llvm::sys::path::begin(CurDir), CurDirIt) == 1) {
-      // The common prefix only the root; stripping it would cause
-      // LLVM diagnostic locations to be more confusing.
-      Dir = {};
-      File = RemappedFile;
-    } else {
-      for (; FileIt != FileE; ++FileIt)
-        llvm::sys::path::append(FileBuf, *FileIt);
-      Dir = DirBuf;
-      File = FileBuf;
-    }
-  } else {
-    Dir = CurDir;
-    File = RemappedFile;
-  }
-  llvm::DIFile *F =
-      DBuilder.createFile(File, Dir, CSInfo,
-                          getSource(SM, SM.getFileID(Loc)));
+  llvm::DIFile *F = DBuilder.createFile(
+      remapDIPath(PLoc.getFilename()), remapDIPath(getCurrentDirname()), CSInfo,
+      getSource(SM, SM.getFileID(Loc)));
 
-  DIFileCache[FileName.data()].reset(F);
+  DIFileCache[fname].reset(F);
   return F;
 }