Pass to emit DWARF path discriminators.

DWARF discriminators are used to distinguish multiple control flow paths
on the same source location. When this happens, instructions across
basic block boundaries will share the same debug location.

This pass detects this situation and creates a new lexical scope to one
of the two instructions. This lexical scope is a child scope of the
original and contains a new discriminator value. This discriminator is
then picked up from MCObjectStreamer::EmitDwarfLocDirective to be
written on the object file.

This fixes http://llvm.org/bugs/show_bug.cgi?id=18270.

llvm-svn: 202752

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/IR/LLVMContextImpl.h b/llvm/lib/IR/LLVMContextImpl.h
index 04338272463..8b94ab1c779 100644
--- a/llvm/lib/IR/LLVMContextImpl.h
+++ b/llvm/lib/IR/LLVMContextImpl.h
@@ -352,7 +352,12 @@ public:
   /// for an index.  The ValueHandle ensures that ScopeINlinedAtIdx stays up
   /// to date.
   std::vector<std::pair<DebugRecVH, DebugRecVH> > ScopeInlinedAtRecords;
-  
+
+  /// DiscriminatorTable - This table maps file:line locations to an
+  /// integer representing the next DWARF path discriminator to assign to
+  /// instructions in different blocks at the same location.
+  DenseMap<std::pair<const char *, unsigned>, unsigned> DiscriminatorTable;
+
   /// IntrinsicIDCache - Cache of intrinsic name (string) to numeric ID mappings
   /// requested in this context
   typedef DenseMap<const Function*, unsigned> IntrinsicIDCacheTy;