[codeview] Ignore .cv_loc directives at the end of a function

If no data or instructions are emitted after a location directive, we
should clear the cv_loc when we change sections, or it will be emitted
at the beginning of the next section. This violates our invariant that
all .cv_loc directives belong to the same section. Add clearer
assertions for this.

llvm-svn: 330884

3 files changed, 19 insertions, 0 deletions

diff --git a/llvm/lib/MC/MCCodeView.cpp b/llvm/lib/MC/MCCodeView.cpp
index 8247db1c622..7d79fc74c18 100644
--- a/llvm/lib/MC/MCCodeView.cpp
+++ b/llvm/lib/MC/MCCodeView.cpp
@@ -472,6 +472,19 @@ void CodeViewContext::encodeInlineLineTable(MCAsmLayout &Layout,
   if (Locs.empty())
     return;
 
+  // Check that the locations are all in the same section.
+#ifndef NDEBUG
+  const MCSection *FirstSec = &Locs.front().getLabel()->getSection();
+  for (const MCCVLineEntry &Loc : Locs) {
+    if (&Loc.getLabel()->getSection() != FirstSec) {
+      errs() << ".cv_loc " << Loc.getFunctionId() << ' ' << Loc.getFileNum()
+             << ' ' << Loc.getLine() << ' ' << Loc.getColumn()
+             << " is in the wrong section\n";
+      llvm_unreachable(".cv_loc crosses sections");
+    }
+  }
+#endif
+
   // Make an artificial start location using the function start and the inlinee
   // lines start location information. All deltas start relative to this
   // location.
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index 69c10f535e5..ac9259a4d24 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -570,6 +570,11 @@ CodeViewContext &MCContext::getCVContext() {
   return *CVContext.get();
 }
 
+void MCContext::clearCVLocSeen() {
+  if (CVContext)
+    CVContext->clearCVLocSeen();
+}
+
 //===----------------------------------------------------------------------===//
 // Error Reporting
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index 0a684588110..316a3be8d89 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -247,6 +247,7 @@ bool MCObjectStreamer::changeSectionImpl(MCSection *Section,
                                          const MCExpr *Subsection) {
   assert(Section && "Cannot switch to a null section!");
   flushPendingLabels(nullptr);
+  getContext().clearCVLocSeen();
   getContext().clearDwarfLocSeen();
 
   bool Created = getAssembler().registerSection(*Section);