[codeview] Emit S_BUILDINFO and LF_BUILDINFO with cwd and source file

Summary: We can fill in the command line and compiler path later if we want.

Reviewers: zturner

Subscribers: hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D53179

llvm-svn: 344393

2 files changed, 50 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 8232f076a93..3b503b683a0 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -561,6 +561,11 @@ void CodeViewDebug::endModule() {
   OS.AddComment("String table");
   OS.EmitCVStringTableDirective();
 
+  // Emit S_BUILDINFO, which points to LF_BUILDINFO. Put this in its own symbol
+  // subsection in the generic .debug$S section at the end. There is no
+  // particular reason for this ordering other than to match MSVC.
+  emitBuildInfo();
+
   // Emit type information and hashes last, so that any types we translate while
   // emitting function info are included.
   emitTypeInformation();
@@ -772,6 +777,49 @@ void CodeViewDebug::emitCompilerInformation() {
   OS.EmitLabel(CompilerEnd);
 }
 
+static TypeIndex getStringIdTypeIdx(GlobalTypeTableBuilder &TypeTable,
+                                    StringRef S) {
+  StringIdRecord SIR(TypeIndex(0x0), S);
+  return TypeTable.writeLeafType(SIR);
+}
+
+void CodeViewDebug::emitBuildInfo() {
+  // First, make LF_BUILDINFO. It's a sequence of strings with various bits of
+  // build info. The known prefix is:
+  // - Absolute path of current directory
+  // - Compiler path
+  // - Main source file path, relative to CWD or absolute
+  // - Type server PDB file
+  // - Canonical compiler command line
+  // If frontend and backend compilation are separated (think llc or LTO), it's
+  // not clear if the compiler path should refer to the executable for the
+  // frontend or the backend. Leave it blank for now.
+  TypeIndex BuildInfoArgs[BuildInfoRecord::MaxArgs] = {};
+  NamedMDNode *CUs = MMI->getModule()->getNamedMetadata("llvm.dbg.cu");
+  const MDNode *Node = *CUs->operands().begin(); // FIXME: Multiple CUs.
+  const auto *CU = cast<DICompileUnit>(Node);
+  const DIFile *MainSourceFile = CU->getFile();
+  BuildInfoArgs[BuildInfoRecord::CurrentDirectory] =
+      getStringIdTypeIdx(TypeTable, MainSourceFile->getDirectory());
+  BuildInfoArgs[BuildInfoRecord::SourceFile] =
+      getStringIdTypeIdx(TypeTable, MainSourceFile->getFilename());
+  // FIXME: Path to compiler and command line. PDB is intentionally blank unless
+  // we implement /Zi type servers.
+  BuildInfoRecord BIR(BuildInfoArgs);
+  TypeIndex BuildInfoIndex = TypeTable.writeLeafType(BIR);
+
+  // Make a new .debug$S subsection for the S_BUILDINFO record, which points
+  // from the module symbols into the type stream.
+  MCSymbol *BuildInfoEnd = beginCVSubsection(DebugSubsectionKind::Symbols);
+  OS.AddComment("Record length");
+  OS.EmitIntValue(6, 2);
+  OS.AddComment("Record kind: S_BUILDINFO");
+  OS.EmitIntValue(unsigned(SymbolKind::S_BUILDINFO), 2);
+  OS.AddComment("LF_BUILDINFO index");
+  OS.EmitIntValue(BuildInfoIndex.getIndex(), 4);
+  endCVSubsection(BuildInfoEnd);
+}
+
 void CodeViewDebug::emitInlineeLinesSubsection() {
   if (InlinedSubprograms.empty())
     return;
diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
index b97092a642e..b6fbdc1373f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.h
@@ -272,6 +272,8 @@ class LLVM_LIBRARY_VISIBILITY CodeViewDebug : public DebugHandlerBase {
 
   void emitCompilerInformation();
 
+  void emitBuildInfo();
+
   void emitInlineeLinesSubsection();
 
   void emitDebugInfoForThunk(const Function *GV,