[DebugInfo] Support DWARF v5 source code embedding extension

In DWARF v5 the Line Number Program Header is extensible, allowing values with
new content types. In this extension a content type is added,
DW_LNCT_LLVM_source, which contains the embedded source code of the file.

Add new optional attribute for !DIFile IR metadata called source which contains
source text. Use this to output the source to the DWARF line table of code
objects. Analogously extend METADATA_FILE in Bitcode and .file directive in ASM
to support optional source.

Teach llvm-dwarfdump and llvm-objdump about the new values. Update the output
format of llvm-dwarfdump to make room for the new attribute on file_names
entries, and support embedded sources for the -source option in llvm-objdump.

Differential Revision: https://reviews.llvm.org/D42765

llvm-svn: 325970

1 files changed, 41 insertions, 10 deletions

diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index 1f0fa78bffc..685b46a606d 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -11,7 +11,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Hashing.h"
-#include "llvm/ADT/None.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
@@ -373,8 +373,13 @@ void MCDwarfLineTableHeader::emitV5FileDirTables(
 
   // The file format, which is the inline null-terminated filename and a
   // directory index.  We don't track file size/timestamp so don't emit them
-  // in the v5 table.  Emit MD5 checksums if we have them.
-  MCOS->EmitIntValue(HasMD5 ? 3 : 2, 1);
+  // in the v5 table.  Emit MD5 checksums and source if we have them.
+  uint64_t Entries = 2;
+  if (HasMD5)
+    Entries += 1;
+  if (HasSource)
+    Entries += 1;
+  MCOS->EmitIntValue(Entries, 1);
   MCOS->EmitULEB128IntValue(dwarf::DW_LNCT_path);
   MCOS->EmitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
                                     : dwarf::DW_FORM_string);
@@ -384,6 +389,11 @@ void MCDwarfLineTableHeader::emitV5FileDirTables(
     MCOS->EmitULEB128IntValue(dwarf::DW_LNCT_MD5);
     MCOS->EmitULEB128IntValue(dwarf::DW_FORM_data16);
   }
+  if (HasSource) {
+    MCOS->EmitULEB128IntValue(dwarf::DW_LNCT_LLVM_source);
+    MCOS->EmitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
+                                      : dwarf::DW_FORM_string);
+  }
   // Then the list of file names. These start at 1.
   MCOS->EmitULEB128IntValue(MCDwarfFiles.size() - 1);
   for (unsigned i = 1; i < MCDwarfFiles.size(); ++i) {
@@ -401,6 +411,15 @@ void MCDwarfLineTableHeader::emitV5FileDirTables(
           StringRef(reinterpret_cast<const char *>(Cksum->Bytes.data()),
                     Cksum->Bytes.size()));
     }
+    if (HasSource) {
+      if (LineStr)
+        LineStr->emitRef(MCOS, MCDwarfFiles[i].Source.getValueOr(StringRef()));
+      else {
+        MCOS->EmitBytes(
+            MCDwarfFiles[i].Source.getValueOr(StringRef())); // Source and...
+        MCOS->EmitBytes(StringRef("\0", 1)); // its null terminator.
+      }
+    }
   }
 }
 
@@ -500,14 +519,17 @@ void MCDwarfLineTable::EmitCU(MCObjectStreamer *MCOS,
 Expected<unsigned> MCDwarfLineTable::tryGetFile(StringRef &Directory,
                                                 StringRef &FileName,
                                                 MD5::MD5Result *Checksum,
+                                                Optional<StringRef> Source,
                                                 unsigned FileNumber) {
-  return Header.tryGetFile(Directory, FileName, Checksum, FileNumber);
+  return Header.tryGetFile(Directory, FileName, Checksum, Source, FileNumber);
 }
 
-Expected<unsigned> MCDwarfLineTableHeader::tryGetFile(StringRef &Directory,
-                                                      StringRef &FileName,
-                                                      MD5::MD5Result *Checksum,
-                                                      unsigned FileNumber) {
+Expected<unsigned>
+MCDwarfLineTableHeader::tryGetFile(StringRef &Directory,
+                                   StringRef &FileName,
+                                   MD5::MD5Result *Checksum,
+                                   Optional<StringRef> &Source,
+                                   unsigned FileNumber) {
   if (Directory == CompilationDir)
     Directory = "";
   if (FileName.empty()) {
@@ -515,9 +537,11 @@ Expected<unsigned> MCDwarfLineTableHeader::tryGetFile(StringRef &Directory,
     Directory = "";
   }
   assert(!FileName.empty());
-  // If any files have an MD5 checksum, they all must.
-  if (MCDwarfFiles.empty())
+  // If any files have an MD5 checksum or embedded source, they all must.
+  if (MCDwarfFiles.empty()) {
     HasMD5 = (Checksum != nullptr);
+    HasSource = (Source != None);
+  }
   if (FileNumber == 0) {
     // File numbers start with 1 and/or after any file numbers
     // allocated by inline-assembler .file directives.
@@ -545,6 +569,10 @@ Expected<unsigned> MCDwarfLineTableHeader::tryGetFile(StringRef &Directory,
   if (HasMD5 != (Checksum != nullptr))
     return make_error<StringError>("inconsistent use of MD5 checksums",
                                    inconvertibleErrorCode());
+  // If any files have embedded source, they all must.
+  if (HasSource != (Source != None))
+    return make_error<StringError>("inconsistent use of embedded source",
+                                   inconvertibleErrorCode());
 
   if (Directory.empty()) {
     // Separate the directory part from the basename of the FileName.
@@ -582,6 +610,9 @@ Expected<unsigned> MCDwarfLineTableHeader::tryGetFile(StringRef &Directory,
   File.Checksum = Checksum;
   if (Checksum)
     HasMD5 = true;
+  File.Source = Source;
+  if (Source)
+    HasSource = true;
 
   // return the allocated FileNumber.
   return FileNumber;