Index: llvm/trunk/include/llvm/Transforms/IPO/LowerBitSets.h
===================================================================
--- llvm/trunk/include/llvm/Transforms/IPO/LowerBitSets.h
+++ llvm/trunk/include/llvm/Transforms/IPO/LowerBitSets.h
@@ -28,6 +28,7 @@
 class DataLayout;
 class GlobalVariable;
 class Value;
+class raw_ostream;
 
 struct BitSetInfo {
   // The indices of the set bits in the bitset.
@@ -57,6 +58,8 @@
   bool containsValue(const DataLayout &DL,
                      const DenseMap<GlobalVariable *, uint64_t> &GlobalLayout,
                      Value *V, uint64_t COffset = 0) const;
+
+  void print(raw_ostream &OS) const;
 };
 
 struct BitSetBuilder {
Index: llvm/trunk/lib/Transforms/IPO/LowerBitSets.cpp
===================================================================
--- llvm/trunk/lib/Transforms/IPO/LowerBitSets.cpp
+++ llvm/trunk/lib/Transforms/IPO/LowerBitSets.cpp
@@ -26,6 +26,8 @@
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 
 using namespace llvm;
@@ -90,6 +92,22 @@
   return false;
 }
 
+void BitSetInfo::print(raw_ostream &OS) const {
+  OS << "offset " << ByteOffset << " size " << BitSize << " align "
+     << (1 << AlignLog2);
+
+  if (isAllOnes()) {
+    OS << " all-ones\n";
+    return;
+  }
+
+  OS << " { ";
+  for (uint64_t B : Bits)
+    OS << B << ' ';
+  OS << "}\n";
+  return;
+}
+
 BitSetInfo BitSetBuilder::build() {
   if (Min > Max)
     Min = 0;
@@ -532,6 +550,10 @@
   for (MDString *BS : BitSets) {
     // Build the bitset.
     BitSetInfo BSI = buildBitSet(BS, GlobalLayout);
+    DEBUG({
+      dbgs() << BS->getString() << ": ";
+      BSI.print(dbgs());
+    });
 
     ByteArrayInfo *BAI = 0;