Fix segmentation fault when mixing -Rpass with #line.

[dnovillo]

Summary

When using #line directives, FileManager::getFile() will return a nil
entry. This triggers an assert in translateFileLineCol().

This patch handles nil FileEntry instances by emitting a not that the
location could not be translated back to a SourceLocation. I don't
really like this solution, but I could not find a way of handling it
any other way.

[dnovillo]

• Check for positive line numbers.

The translation to SourceLocation does not understand line number 0.
That means that the associated instruction did not really have location
information attached to it.

[rsmith]

LGTM, although this makes the "do this properly" FIXME seem somewhat more of a pressing concern :)

lib/CodeGen/CodeGenAction.cpp

405

How does SourceMgr respond if the file/line you give it is out of range for the file?

include/clang/Basic/DiagnosticFrontendKinds.td

 def remark_fe_backend_plugin: Remark<"%0">, CatBackend, InGroup<RemarkBackendPlugin>;
 def note_fe_backend_plugin: Note<"%0">, CatBackend;
 
 def remark_fe_backend_optimization_remark : Remark<"%0">, CatBackend,
     InGroup<BackendOptimizationRemark>, DefaultRemark;
 def note_fe_backend_optimization_remark_missing_loc : Note<"use "
   "-gline-tables-only -gcolumn-info to track source location information "
   "for this optimization remark">;
+def note_fe_backend_optimization_remark_invalid_loc : Note<"could "
+  "not determine the original source location for %0:%1:%2">;
 
 def err_fe_invalid_code_complete_file : Error<
     "cannot locate code-completion file %0">, DefaultFatal;
 def err_fe_stdout_binary : Error<"unable to change standard output to binary">,
   DefaultFatal;
 def err_fe_dependency_file_requires_MT : Error<
     "-dependency-file requires at least one -MT or -MQ option">;
 def err_fe_invalid_plugin_name : Error<

lib/CodeGen/CodeGenAction.cpp

void BackendConsumer::OptimizationRemarkHandler(
   if (CodeGenOpts.OptimizationRemarkPattern &&
       CodeGenOpts.OptimizationRemarkPattern->match(D.getPassName())) {
     SourceManager &SourceMgr = Context->getSourceManager();
     FileManager &FileMgr = SourceMgr.getFileManager();
     StringRef Filename;
     unsigned Line, Column;
     D.getLocation(&Filename, &Line, &Column);
     SourceLocation Loc;
-    if (Line > 0) {
+    const FileEntry *FE = FileMgr.getFile(Filename);
+    if (FE && Line > 0) {
       // If -gcolumn-info was not used, Column will be 0. This upsets the
       // source manager, so if Column is not set, set it to 1.
       if (Column == 0)
         Column = 1;
-      Loc = SourceMgr.translateFileLineCol(FileMgr.getFile(Filename), Line,
-                                           Column);
+      Loc = SourceMgr.translateFileLineCol(FE, Line, Column);
     }
     Diags.Report(Loc, diag::remark_fe_backend_optimization_remark)
         << AddFlagValue(D.getPassName()) << D.getMsg().str();
 
     if (Line == 0)
       // If we could not extract a source location for the diagnostic,
       // inform the user how they can get source locations back.
       //
       // FIXME: We should really be generating !srcloc annotations when
       // -Rpass is used. !srcloc annotations need to be emitted in
       // approximately the same spots as !dbg nodes.
       Diags.Report(diag::note_fe_backend_optimization_remark_missing_loc);
+    else if (Loc.isInvalid())
+      // If we were not able to translate the file:line:col information
+      // back to a SourceLocation, at least emit a note stating that
+      // we could not translate this location. This can happen in the
+      // case of #line directives.
+      Diags.Report(diag::note_fe_backend_optimization_remark_invalid_loc)
+        << Filename << Line << Column;
   }
 }
 
 /// \brief This function is invoked when the backend needs
 /// to report something to the user.
 void BackendConsumer::DiagnosticHandlerImpl(const DiagnosticInfo &DI) {
   unsigned DiagID = diag::err_fe_inline_asm;
   llvm::DiagnosticSeverity Severity = DI.getSeverity();

test/Frontend/optimization-remark-line-directive.c

+// This file tests -Rpass diagnostics together with #line
+// directives. We cannot map #line directives back to
+// a SourceLocation.
+
+// RUN: %clang -c %s -Rpass=inline -O0 -S -gmlt -o /dev/null 2> %t.err
+// RUN: FileCheck < %t.err %s --check-prefix=INLINE-INVALID-LOC
+//
+int foo(int x, int y) __attribute__((always_inline));
+int foo(int x, int y) { return x + y; }
+
+#line 1230 "/bad/path/to/original.c"
+int bar(int j) { return foo(j, j - 2); }
+
+// INLINE-INVALID-LOC: {{^remark: foo inlined into bar}}
+// INLINE-INVALID-LOC: note: could not determine the source location for /bad/path/to/original.c:1230:0