[BOLT][NFC] Resolved all clang-12 warnings for bolt

Summary:
clang-12 now compiles bolt without warnings.
Some warnings were fixed if possible while others were suppressed by
doing (void)variable for unused variable warnings or moving code inside
assert statements of LLVM_DEBUG blocks.

(cherry picked from FBD29469054)

bolt/src/BinaryContext.cpp

@@ -1750,6 +1750,7 @@ BinaryContext::getSectionNameForAddress(uint64_t Address) const {
 
 BinarySection &BinaryContext::registerSection(BinarySection *Section) {
   auto Res = Sections.insert(Section);
+  (void)Res;
   assert(Res.second && "can't register the same section twice.");
 
   // Only register allocatable sections in the AddressToSection map.
@@ -1787,6 +1788,7 @@ BinarySection &BinaryContext::registerOrUpdateSection(StringRef Name,
 
     LLVM_DEBUG(dbgs() << "BOLT-DEBUG: updating " << *Section << " -> ");
     const bool Flag = Section->isAllocatable();
+    (void)Flag;
     Section->update(Data, Size, Alignment, ELFType, ELFFlags);
     LLVM_DEBUG(dbgs() << *Section << "\n");
     // FIXME: Fix section flags/attributes for MachO.

bolt/src/BinaryFunction.cpp

@@ -3926,6 +3926,7 @@ bool BinaryFunction::replaceJumpTableEntryIn(BinaryBasicBlock *BB,
   assert(JT && "No jump table structure for this indirect branch");
   bool Patched = JT->replaceDestination(JTAddress, OldDest->getLabel(),
                                         NewDest->getLabel());
+  (void)Patched;
   assert(Patched && "Invalid entry to be replaced in jump table");
   return true;
 }

bolt/src/DWARFRewriter.cpp

@@ -168,6 +168,7 @@ void DWARFRewriter::updateDebugInfo() {
     uint64_t AttrOffset = 0;
     Optional<DWARFFormValue> ValDwoName =
         DIE.find(dwarf::DW_AT_GNU_dwo_name, &AttrOffset);
+    (void)ValDwoName;
     assert(ValDwoName && "Skeleton CU doesn't have dwo_name.");
 
     std::string ObjectName = getDWOName(Unit, &NameToIndexMap, DWOIdToName);
@@ -176,6 +177,7 @@ void DWARFRewriter::updateDebugInfo() {
 
     Optional<DWARFFormValue> ValCompDir =
         DIE.find(dwarf::DW_AT_comp_dir, &AttrOffset);
+    (void)ValCompDir;
     assert(ValCompDir && "DW_AT_comp_dir is not in Skeleton CU.");
     if (!opts::DwoOutputPath.empty()) {
       uint32_t NewOffset = StrWriter->addString(opts::DwoOutputPath.c_str());

bolt/src/DebugData.cpp

@@ -228,6 +228,7 @@ AddressSectionBuffer DebugAddrWriter::finalize() {
       switch (AddrSize) {
       default:
         assert(false && "Address Size is invalid.");
+        break;
       case 4:
         support::endian::write(AddressStream, static_cast<uint32_t>(Address),
                                support::little);

bolt/src/ParallelUtilities.cpp

@@ -212,6 +212,7 @@ void runOnEachFunctionWithUniqueAllocId(
       if (!BC.MIB->checkAllocatorExists(AllocId)) {
         MCPlusBuilder::AllocatorIdTy Id =
             BC.MIB->initializeNewAnnotationAllocator();
+        (void)Id;
         assert(AllocId == Id && "unexpected allocator id created");
       }
       Pool.async(runBlock, BlockBegin, std::next(It), AllocId);
@@ -224,6 +225,7 @@ void runOnEachFunctionWithUniqueAllocId(
   if (!BC.MIB->checkAllocatorExists(AllocId)) {
     MCPlusBuilder::AllocatorIdTy Id =
         BC.MIB->initializeNewAnnotationAllocator();
+    (void)Id;
     assert(AllocId == Id && "unexpected allocator id created");
   }
 

bolt/src/Passes/ExtTSPReorderAlgorithm.cpp

@@ -785,6 +785,7 @@ class ExtTSP {
         Block *BB2 = ChainPred->blocks()[Offset];
         // Does the splitting break FT successors?
         if (BB1->FallthroughSucc != nullptr) {
+          (void)BB2;
           assert(BB1->FallthroughSucc == BB2 && "Fallthrough not preserved");
           continue;
         }
@@ -850,8 +851,6 @@ class ExtTSP {
         return MergedChain(BeginY, EndY, BeginX2, EndX2, BeginX1, EndX1);
       case MergeTypeTy::X2_X1_Y:
         return MergedChain(BeginX2, EndX2, BeginX1, EndX1, BeginY, EndY);
-      default:
-        llvm_unreachable("unexpected merge type");
     }
   }
 

bolt/src/Passes/IndirectCallPromotion.cpp

@@ -1550,6 +1550,7 @@ void IndirectCallPromotion::runOnFunctions(BinaryContext &BC) {
                    std::max<uint64_t>(TotalIndexBasedCandidates, 1))
          << "%\n";
 
+  (void)verifyProfile;
 #ifndef NDEBUG
   verifyProfile(BFs);
 #endif

bolt/src/Passes/ShrinkWrapping.cpp

@@ -1303,6 +1303,7 @@ void ShrinkWrapping::moveSaveRestores() {
 
     const FrameIndexEntry *FIESave = CSA.SaveFIEByReg[I];
     const FrameIndexEntry *FIELoad = CSA.LoadFIEByReg[I];
+    (void)FIELoad;
     assert(FIESave && FIELoad);
     StackPointerTracking &SPT = Info.getStackPointerTracking();
     const std::pair<int, int> SPFP = *SPT.getStateBefore(*BestPosSave);
@@ -2003,6 +2004,7 @@ bool ShrinkWrapping::perform() {
   processDeletions();
   if (foldIdenticalSplitEdges()) {
     const std::pair<unsigned, uint64_t> Stats = BF.eraseInvalidBBs();
+    (void)Stats;
     LLVM_DEBUG(dbgs() << "Deleted " << Stats.first
                       << " redundant split edge BBs (" << Stats.second
                       << " bytes) for " << BF.getPrintName() << "\n");

bolt/src/RewriteInstance.cpp

@@ -1944,6 +1944,7 @@ bool RewriteInstance::analyzeRelocation(const RelocationRef &Rel,
            truncateToSize(SymbolAddress + Addend - PCRelOffset, RelSize);
   };
 
+  (void)verifyExtractedValue;
   assert(verifyExtractedValue() && "mismatched extracted relocation value");
 
   return true;
@@ -2164,9 +2165,8 @@ void RewriteInstance::processLKBugTable() {
            "Reading valid PC-relative offset for a __bug_table entry");
     const int32_t SignedOffset = *Offset;
     const uint64_t RefAddress = EntryAddress + SignedOffset;
-    BinaryFunction *ContainingBF =
-        BC->getBinaryFunctionContainingAddress(RefAddress);
-    assert(ContainingBF && "__bug_table entries should point to a function");
+    assert(BC->getBinaryFunctionContainingAddress(RefAddress) &&
+           "__bug_table entries should point to a function");
 
     insertLKMarker(RefAddress, I, SignedOffset, true, "__bug_table");
   }
@@ -2205,9 +2205,11 @@ void RewriteInstance::processLKSMPLocks() {
 void RewriteInstance::readDynamicRelocations(const SectionRef &Section) {
   assert(BinarySection(*BC, Section).isAllocatable() && "allocatable expected");
 
-  StringRef SectionName = cantFail(Section.getName());
-  LLVM_DEBUG(dbgs() << "BOLT-DEBUG: reading relocations for section "
-                    << SectionName << ":\n");
+  LLVM_DEBUG({
+    StringRef SectionName = cantFail(Section.getName());
+    dbgs() << "BOLT-DEBUG: reading relocations for section " << SectionName
+           << ":\n";
+  });
 
   for (const RelocationRef &Rel : Section.relocations()) {
     uint64_t RType = Rel.getType();
@@ -2243,9 +2245,11 @@ void RewriteInstance::readDynamicRelocations(const SectionRef &Section) {
 }
 
 void RewriteInstance::readRelocations(const SectionRef &Section) {
-  StringRef SectionName = cantFail(Section.getName());
-  LLVM_DEBUG(dbgs() << "BOLT-DEBUG: reading relocations for section "
-                    << SectionName << ":\n");
+  LLVM_DEBUG({
+    StringRef SectionName = cantFail(Section.getName());
+    dbgs() << "BOLT-DEBUG: reading relocations for section " << SectionName
+           << ":\n";
+  });
   if (BinarySection(*BC, Section).isAllocatable()) {
     LLVM_DEBUG(dbgs() << "BOLT-DEBUG: ignoring runtime relocations\n");
     return;