Add a -verify-linetable LLVM option.

lib/IRGen/IRGenDebugInfo.cpp

@@ -58,6 +58,11 @@
 using namespace swift;
 using namespace irgen;
 
+llvm::cl::opt<bool> VerifyLineTable(
+    "verify-linetable", llvm::cl::init(false),
+    llvm::cl::desc(
+        "Verify that the debug locations within one scope are contiguous."));
+
 namespace {
 using TrackingDIRefMap =
     llvm::DenseMap<const llvm::MDString *, llvm::TrackingMDNodeRef>;
@@ -105,6 +110,20 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
   SmallVector<std::pair<SILLocation::DebugLoc, const SILDebugScope *>, 8>
       LocationStack;
 
+#ifndef NDEBUG
+  using UUSTuple = std::pair<std::pair<unsigned, unsigned>, StringRef>;
+  struct DebugLocKey : public UUSTuple {
+    DebugLocKey(SILLocation::DebugLoc DL)
+        : UUSTuple({{DL.Line, DL.Column}, DL.Filename}) {}
+    inline bool operator==(const SILLocation::DebugLoc &DL) const {
+      return first.first == DL.Line && first.second == DL.Column &&
+             second.equals(DL.Filename);
+    }
+  };
+  llvm::DenseSet<UUSTuple> PreviousLineEntries;
+  SILLocation::DebugLoc PreviousDebugLoc;
+#endif
+
 public:
   IRGenDebugInfoImpl(const IRGenOptions &Opts, ClangImporter &CI,
                      IRGenModule &IGM, llvm::Module &M,
@@ -307,6 +326,10 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
     }
     return true;
   }
+
+  /// Assert that within one lexical block, each location is only visited once.
+  bool lineEntryIsSane(SILLocation::DebugLoc DL, const SILDebugScope *DS);
+
 #endif
 
   llvm::DIFile *getOrCreateFile(StringRef Filename) {
@@ -1564,6 +1587,23 @@ void IRGenDebugInfoImpl::finalize() {
   DBuilder.finalize();
 }
 
+bool IRGenDebugInfoImpl::lineEntryIsSane(SILLocation::DebugLoc DL,
+                                         const SILDebugScope *DS) {
+  // All bets are off for optimized code.
+  if (!VerifyLineTable || Opts.shouldOptimize())
+    return true;
+  // We entered a new lexical block.
+  if (DS != LastScope)
+    PreviousLineEntries.clear();
+  if (DL.Line == 0 || DL == PreviousDebugLoc)
+    return true;
+  // Save the last non-zero line entry.
+  PreviousDebugLoc = DL;
+  auto ItNew = PreviousLineEntries.insert(DebugLocKey(DL));
+  // Return true iff DL was not yet in PreviousLineEntries.
+  return ItNew.second;
+}
+
 void IRGenDebugInfoImpl::setCurrentLoc(IRBuilder &Builder,
                                        const SILDebugScope *DS,
                                        SILLocation Loc) {
@@ -1612,9 +1652,8 @@ void IRGenDebugInfoImpl::setCurrentLoc(IRBuilder &Builder,
   }
 
   // FIXME: Enable this assertion.
-  // assert(lineNumberIsSane(Builder, L.Line) &&
-  //       "-Onone, but line numbers are not monotonically increasing within
-  //       bb");
+  assert(lineEntryIsSane(L, DS) &&
+         "non-contiguous debug location in same scope at -Onone");
   LastDebugLoc = L;
   LastScope = DS;