[DWARF] Fix mixing assembler -g with DWARF .file directives.

We were effectively overriding an explicit '.file' directive with info
for the assembler source.  That shouldn't happen.

Fixes PR36636, really, even for .s files emitted by Clang.

Differential Revision: https://reviews.llvm.org/D44265

llvm-svn: 328208

1 files changed, 32 insertions, 16 deletions

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 54a76732bbe..3042f9964ff 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -311,6 +311,11 @@ private:
   }
   static void DiagHandler(const SMDiagnostic &Diag, void *Context);
 
+  /// Should we emit DWARF describing this assembler source?  (Returns false if
+  /// the source has .file directives, which means we don't want to generate
+  /// info describing the assembler source itself.)
+  bool enabledGenDwarfForAssembly();
+
   /// \brief Enter the specified file. This returns true on failure.
   bool enterIncludeFile(const std::string &Filename);
 
@@ -824,6 +829,19 @@ const AsmToken &AsmParser::Lex() {
   return *tok;
 }
 
+bool AsmParser::enabledGenDwarfForAssembly() {
+  // Check whether the user specified -g.
+  if (!getContext().getGenDwarfForAssembly())
+    return false;
+  // If we haven't encountered any .file directives (which would imply that
+  // the assembler source was produced with debug info already) then emit one
+  // describing the assembler source file itself.
+  if (getContext().getGenDwarfFileNumber() == 0)
+    getContext().setGenDwarfFileNumber(getStreamer().EmitDwarfFileDirective(
+        0, StringRef(), getContext().getMainFileName()));
+  return true;
+}
+
 bool AsmParser::Run(bool NoInitialTextSection, bool NoFinalize) {
   // Create the initial section, if requested.
   if (!NoInitialTextSection)
@@ -837,7 +855,9 @@ bool AsmParser::Run(bool NoInitialTextSection, bool NoFinalize) {
   SmallVector<AsmRewrite, 4> AsmStrRewrites;
 
   // If we are generating dwarf for assembly source files save the initial text
-  // section and generate a .file directive.
+  // section.  (Don't use enabledGenDwarfForAssembly() here, as we aren't
+  // emitting any actual debug info yet and haven't had a chance to parse any
+  // embedded .file directives.)
   if (getContext().getGenDwarfForAssembly()) {
     MCSection *Sec = getStreamer().getCurrentSectionOnly();
     if (!Sec->getBeginSymbol()) {
@@ -848,8 +868,6 @@ bool AsmParser::Run(bool NoInitialTextSection, bool NoFinalize) {
     bool InsertResult = getContext().addGenDwarfSection(Sec);
     assert(InsertResult && ".text section should not have debug info yet");
     (void)InsertResult;
-    getContext().setGenDwarfFileNumber(getStreamer().EmitDwarfFileDirective(
-        0, StringRef(), getContext().getMainFileName()));
   }
 
   // While we have input, parse each statement.
@@ -1784,7 +1802,7 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
 
     // If we are generating dwarf for assembly source files then gather the
     // info to make a dwarf label entry for this label if needed.
-    if (getContext().getGenDwarfForAssembly())
+    if (enabledGenDwarfForAssembly())
       MCGenDwarfLabelEntry::Make(Sym, &getStreamer(), getSourceManager(),
                                  IDLoc);
 
@@ -2153,7 +2171,7 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
 
   // If we are generating dwarf for the current section then generate a .loc
   // directive for the instruction.
-  if (!ParseHadError && getContext().getGenDwarfForAssembly() &&
+  if (!ParseHadError && enabledGenDwarfForAssembly() &&
       getContext().getGenDwarfSectionSyms().count(
           getStreamer().getCurrentSectionOnly())) {
     unsigned Line;
@@ -3318,6 +3336,10 @@ bool AsmParser::parseDirectiveFile(SMLoc DirectiveLoc) {
     }
   }
 
+  // In case there is a -g option as well as debug info from directive .file,
+  // we turn off the -g option, directly use the existing debug info instead.
+  getContext().setGenDwarfForAssembly(false);
+
   if (FileNumber == -1)
     getStreamer().EmitFileDirective(Filename);
   else {
@@ -3334,17 +3356,11 @@ bool AsmParser::parseDirectiveFile(SMLoc DirectiveLoc) {
       memcpy(SourceBuf, SourceString.data(), SourceString.size());
       Source = StringRef(SourceBuf, SourceString.size());
     }
-    // If there is -g option as well as debug info from directive file,
-    // we turn off -g option, directly use the existing debug info instead.
-    if (getContext().getGenDwarfForAssembly())
-      getContext().setGenDwarfForAssembly(false);
-    else {
-      Expected<unsigned> FileNumOrErr = getStreamer().tryEmitDwarfFileDirective(
-          FileNumber, Directory, Filename, CKMem, Source);
-      if (!FileNumOrErr)
-        return Error(DirectiveLoc, toString(FileNumOrErr.takeError()));
-      FileNumber = FileNumOrErr.get();
-    }
+    Expected<unsigned> FileNumOrErr = getStreamer().tryEmitDwarfFileDirective(
+        FileNumber, Directory, Filename, CKMem, Source);
+    if (!FileNumOrErr)
+      return Error(DirectiveLoc, toString(FileNumOrErr.takeError()));
+    FileNumber = FileNumOrErr.get();
   }
 
   return false;