Allow retrieving source files relative to the compilation directory.

Summary:
Dwarf stores source-file names the three parts:
<compilation_directory><include_directory><filename>

Prior to this change, the code only allowed retrieving either all
three as the absolute path, or just the filename.  But many
compile-command lines--especially those in hermetic build systems
don't specify an absolute path, nor just the filename, but rather the
path relative to the compilation directory. This features allows
retrieving them in that style.

Add tests for path printing styles.

Modify createBasicPrologue to handle include directories.

Subscribers: aprantl, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73383

llvm/include/llvm/DebugInfo/DIContext.h

@@ -133,7 +133,12 @@ enum class DINameKind { None, ShortName, LinkageName };
 /// Controls which fields of DILineInfo container should be filled
 /// with data.
 struct DILineInfoSpecifier {
-  enum class FileLineInfoKind { None, Default, AbsoluteFilePath };
+  enum class FileLineInfoKind {
+    None,
+    Default,
+    RelativeFilePath,
+    AbsoluteFilePath
+  };
   using FunctionNameKind = DINameKind;
 
   FileLineInfoKind FLIKind;

llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

@@ -1082,7 +1082,7 @@ bool DWARFDebugLine::Prologue::getFileNameByIndex(
   if (!Name)
     return false;
   StringRef FileName = *Name;
-  if (Kind != FileLineInfoKind::AbsoluteFilePath ||
+  if (Kind == FileLineInfoKind::Default ||
       isPathAbsoluteOnWindowsOrPosix(FileName)) {
     Result = std::string(FileName);
     return true;
@@ -1099,12 +1099,17 @@ bool DWARFDebugLine::Prologue::getFileNameByIndex(
       IncludeDir =
           IncludeDirectories[Entry.DirIdx - 1].getAsCString().getValue();
   }
-  // We may still need to append compilation directory of compile unit.
-  // We know that FileName is not absolute, the only way to have an
-  // absolute path at this point would be if IncludeDir is absolute.
-  if (!CompDir.empty() && !isPathAbsoluteOnWindowsOrPosix(IncludeDir))
+  // For absolute paths only, include the compilation directory of compile unit.
+  // We know that FileName is not absolute, the only way to have an absolute
+  // path at this point would be if IncludeDir is absolute.
+  if (Kind == FileLineInfoKind::AbsoluteFilePath && !CompDir.empty() &&
+      !isPathAbsoluteOnWindowsOrPosix(IncludeDir))
     sys::path::append(FilePath, Style, CompDir);
 
+  assert((Kind == FileLineInfoKind::AbsoluteFilePath ||
+          Kind == FileLineInfoKind::RelativeFilePath) &&
+         "invalid FileLineInfo Kind");
+
   // sys::path::append skips empty strings.
   sys::path::append(FilePath, Style, IncludeDir, FileName);
   Result = std::string(FilePath.str());

llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp

@@ -917,4 +917,51 @@ TEST_F(DebugLineBasicFixture, ParserPrintsStandardOpcodesWhenRequested) {
   EXPECT_TRUE(InOutput("0x0000003f: 0c DW_LNS_set_isa (66)\n")) << Output;
 }
 
+TEST_F(DebugLineBasicFixture, PrintPathsProperly) {
+  if (!setupGenerator(5))
+    return;
+
+  LineTable &LT = Gen->addLineTable();
+  DWARFDebugLine::Prologue P = LT.createBasicPrologue();
+  P.IncludeDirectories.push_back(
+      DWARFFormValue::createFromPValue(DW_FORM_string, "b dir"));
+  P.FileNames.push_back(DWARFDebugLine::FileNameEntry());
+  P.FileNames.back().Name =
+      DWARFFormValue::createFromPValue(DW_FORM_string, "b file");
+  P.FileNames.back().DirIdx = 1;
+  P.PrologueLength += 14;
+  LT.setPrologue(P);
+  generate();
+
+  auto ExpectedLineTable = Line.getOrParseLineTable(LineData, 0, *Context,
+                                                    nullptr, RecordRecoverable);
+  EXPECT_THAT_EXPECTED(ExpectedLineTable, Succeeded());
+  std::string Result;
+  // DWARF 5 stores the compilation directory in two places: the Compilation
+  // Unit and the directory table entry 0, and implementations are free to use
+  // one or the other. This copy serves as the one stored in the CU.
+  StringRef CompDir = "a dir";
+  EXPECT_FALSE(
+      (*ExpectedLineTable)
+          ->Prologue.getFileNameByIndex(
+              1, CompDir, DILineInfoSpecifier::FileLineInfoKind::None, Result));
+  EXPECT_TRUE((*ExpectedLineTable)
+                  ->Prologue.getFileNameByIndex(
+                      1, CompDir,
+                      DILineInfoSpecifier::FileLineInfoKind::Default, Result));
+  EXPECT_STREQ(Result.c_str(), "b file");
+  EXPECT_TRUE((*ExpectedLineTable)
+                  ->Prologue.getFileNameByIndex(
+                      1, CompDir,
+                      DILineInfoSpecifier::FileLineInfoKind::RelativeFilePath,
+                      Result));
+  EXPECT_STREQ(Result.c_str(), "b dir/b file");
+  EXPECT_TRUE((*ExpectedLineTable)
+                  ->Prologue.getFileNameByIndex(
+                      1, CompDir,
+                      DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath,
+                      Result));
+  EXPECT_STREQ(Result.c_str(), "a dir/b dir/b file");
+}
+
 } // end anonymous namespace