LowerBitSets: Add debugging output.

[samsonov]

LGTM

include/llvm/Transforms/IPO/LowerBitSets.h

 #include <set>
 #include <vector>
 
 namespace llvm {
 
 class DataLayout;
 class GlobalVariable;
 class Value;
+class raw_ostream;
 
 struct BitSetInfo {
   // The indices of the set bits in the bitset.
   std::set<uint64_t> Bits;
 
   // The byte offset into the combined global represented by the bitset.
   uint64_t ByteOffset;
 
bool isAllOnes() const {
     return Bits.size() == BitSize;
   }
 
   bool containsGlobalOffset(uint64_t Offset) const;
 
   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 {
   SmallVector<uint64_t, 16> Offsets;
   uint64_t Min, Max;
 
   BitSetBuilder() : Min(std::numeric_limits<uint64_t>::max()), Max(0) {}
 

lib/Transforms/IPO/LowerBitSets.cpp

 #include "llvm/IR/Constants.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Intrinsics.h"
 #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;
 
 #define DEBUG_TYPE "lowerbitsets"
 
 STATISTIC(ByteArraySizeBits, "Byte array size in bits");
 STATISTIC(ByteArraySizeBytes, "Byte array size in bytes");
if (auto Op = dyn_cast<Operator>(V)) {
     if (Op->getOpcode() == Instruction::Select)
       return containsValue(DL, GlobalLayout, Op->getOperand(1), COffset) &&
              containsValue(DL, GlobalLayout, Op->getOperand(2), COffset);
   }
 
   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;
 
   // Normalize each offset against the minimum observed offset, and compute
   // the bitwise OR of each of the offsets. The number of trailing zeros
   // in the mask gives us the log2 of the alignment of all offsets, which
   // allows us to compress the bitset by only storing one bit per aligned
void LowerBitSets::buildBitSetsFromGlobals(
   for (unsigned I = 0; I != Globals.size(); ++I)
     // Multiply by 2 to account for padding elements.
     GlobalLayout[Globals[I]] = CombinedGlobalLayout->getElementOffset(I * 2);
 
   // For each bitset in this disjoint set...
   for (MDString *BS : BitSets) {
     // Build the bitset.
     BitSetInfo BSI = buildBitSet(BS, GlobalLayout);
+    DEBUG({
+      dbgs() << BS->getString() << ": ";
+      BSI.print(dbgs());
+    });
 
     ByteArrayInfo *BAI = 0;
 
     // Lower each call to llvm.bitset.test for this bitset.
     for (CallInst *CI : BitSetTestCallSites[BS]) {
       ++NumBitSetCallsLowered;
       Value *Lowered = lowerBitSetCall(CI, BSI, BAI, CombinedGlobal, GlobalLayout);
       CI->replaceAllUsesWith(Lowered);