[DWARFv5] Tolerate files not all having an MD5 checksum.

In some cases, for example when compiling a preprocessed file, the
front-end is not able to provide an MD5 checksum for all files. When
that happens, omit the MD5 checksums from the final DWARF, because
DWARF doesn't have a way to indicate that some but not all files have
a checksum.

When assembling a .s file, and some but not all .file directives
provide an MD5 checksum, issue a warning and don't emit MD5 into the
DWARF.

Fixes PR37623.

Differential Revision: https://reviews.llvm.org/D48135

llvm-svn: 334710

1 files changed, 14 insertions, 1 deletions

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 5c8946b286b..39922611e0e 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -177,6 +177,9 @@ private:
   /// Are we parsing ms-style inline assembly?
   bool ParsingInlineAsm = false;
 
+  /// Did we already inform the user about inconsistent MD5 usage?
+  bool ReportedInconsistentMD5 = false;
+
 public:
   AsmParser(SourceMgr &SM, MCContext &Ctx, MCStreamer &Out,
             const MCAsmInfo &MAI, unsigned CB);
@@ -3337,7 +3340,11 @@ 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);
+  // Also reset any implicit ".file 0" for the assembler source.
+  if (Ctx.getGenDwarfForAssembly()) {
+    Ctx.getMCDwarfLineTable(0).resetRootFile();
+    Ctx.setGenDwarfForAssembly(false);
+  }
 
   if (FileNumber == -1)
     getStreamer().EmitFileDirective(Filename);
@@ -3364,6 +3371,12 @@ bool AsmParser::parseDirectiveFile(SMLoc DirectiveLoc) {
         return Error(DirectiveLoc, toString(FileNumOrErr.takeError()));
       FileNumber = FileNumOrErr.get();
     }
+    // Alert the user if there are some .file directives with MD5 and some not.
+    // But only do that once.
+    if (!ReportedInconsistentMD5 && !Ctx.isDwarfMD5UsageConsistent(0)) {
+      ReportedInconsistentMD5 = true;
+      return Warning(DirectiveLoc, "inconsistent use of MD5 checksums");
+    }
   }
 
   return false;