Iterate DenseMaps with auto and structured bindings. NFC (llvm#221869)

Avoid naming `std::pair` directly. The DenseMap bucket is subject to
change (llvm#221853).

Author: MaskRay

clang/lib/Sema/SemaAttr.cpp

@@ -1074,7 +1074,7 @@ void Sema::ActOnPragmaAttributeAttribute(
     //    variable(is_parameter).
     //  - a sub-rule and a sibling that's negated. E.g.
     //    variable(is_thread_local) and variable(unless(is_parameter))
-    llvm::SmallDenseMap<int, std::pair<int, SourceRange>, 2>
+    llvm::SmallDenseMap<int, attr::ParsedSubjectMatchRuleSet::value_type, 2>
         RulesToFirstSpecifiedNegatedSubRule;
     for (const auto &Rule : Rules) {
       attr::SubjectMatchRule MatchRule = attr::SubjectMatchRule(Rule.first);

llvm/lib/Bitcode/Reader/MetadataLoader.cpp

@@ -241,8 +241,8 @@ void BitcodeReaderMetadataList::tryToResolveCycles() {
     return;
 
   // Give up on finding a full definition for any forward decls that remain.
-  for (const auto &Ref : OldTypeRefs.FwdDecls)
-    OldTypeRefs.Final.insert(Ref);
+  for (const auto &[UUID, CT] : OldTypeRefs.FwdDecls)
+    OldTypeRefs.Final.try_emplace(UUID, CT);
   OldTypeRefs.FwdDecls.clear();
 
   // Upgrade from old type ref arrays.  In strange cases, this could add to

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -579,12 +579,12 @@ class IndexBitcodeWriter : public BitcodeWriterBase {
   void forEachSummary(Functor Callback) {
     if (ModuleToSummariesForIndex) {
       for (auto &M : *ModuleToSummariesForIndex)
-        for (auto &Summary : M.second) {
-          Callback(Summary, false);
+        for (auto &[GUID, GVS] : M.second) {
+          Callback({GUID, GVS}, false);
           // Ensure aliasee is handled, e.g. for assigning a valueId,
           // even if we are not importing the aliasee directly (the
           // imported alias will contain a copy of aliasee).
-          if (auto *AS = dyn_cast<AliasSummary>(Summary.getSecond()))
+          if (auto *AS = dyn_cast<AliasSummary>(GVS))
             Callback({AS->getAliaseeGUID(), &AS->getAliasee()}, true);
         }
     } else {

llvm/lib/CodeGen/RegisterUsageInfo.cpp

@@ -70,7 +70,7 @@ PhysicalRegisterUsageInfo::getRegUsageInfo(const Function &FP) {
 }
 
 void PhysicalRegisterUsageInfo::print(raw_ostream &OS, const Module *M) const {
-  using FuncPtrRegMaskPair = std::pair<const Function *, std::vector<uint32_t>>;
+  using FuncPtrRegMaskPair = decltype(RegMasks)::value_type;
 
   // Create a vector of pointer to RegMasks entries
   SmallVector<const FuncPtrRegMaskPair *, 64> FPRMPairVector(

llvm/lib/CodeGen/StackColoring.cpp

@@ -927,7 +927,7 @@ void StackColoring::remapInstructions(DenseMap<int, int> &SlotRemap) {
   // Keep a list of allocas which has been affected by the remap.
   SmallPtrSet<const AllocaInst*, 32> MergedAllocas;
 
-  for (const std::pair<int, int> &SI : SlotRemap) {
+  for (const auto &SI : SlotRemap) {
     const AllocaInst *From = MFI->getObjectAllocation(SI.first);
     const AllocaInst *To = MFI->getObjectAllocation(SI.second);
     assert(To && From && "Invalid allocation object");

llvm/lib/MC/StringTableBuilder.cpp

@@ -66,7 +66,7 @@ void StringTableBuilder::write(raw_ostream &OS) const {
   OS << Data;
 }
 
-using StringPair = std::pair<CachedHashStringRef, size_t>;
+using StringPair = DenseMap<CachedHashStringRef, size_t>::value_type;
 
 void StringTableBuilder::write(uint8_t *Buf) const {
   assert(isFinalized());

llvm/lib/MCA/HardwareUnits/LSUnit.cpp

@@ -42,7 +42,7 @@ LSUnitBase::LSUnitBase(const MCSchedModel &SM, unsigned LQ, unsigned SQ,
 LSUnitBase::~LSUnitBase() = default;
 
 void LSUnit::cycleEvent() {
-  for (const std::pair<unsigned, std::unique_ptr<MemoryGroup>> &G : Groups)
+  for (const auto &G : Groups)
     G.second->cycleEvent();
 }
 

llvm/lib/MCA/HardwareUnits/ResourceManager.cpp

@@ -473,7 +473,7 @@ void ResourceManager::fastIssueInstruction(
 }
 
 void ResourceManager::cycleEvent(SmallVectorImpl<ResourceRef> &ResourcesFreed) {
-  for (std::pair<ResourceRef, unsigned> &BR : BusyResources) {
+  for (auto &BR : BusyResources) {
     if (BR.second)
       BR.second--;
     if (!BR.second) {

llvm/lib/Transforms/IPO/SampleProfile.cpp

@@ -2205,9 +2205,8 @@ bool SampleProfileLoader::runOnModule(Module &M, ModuleAnalysisManager &AM,
 
   // Account for cold calls not inlined....
   if (!FunctionSamples::ProfileIsCS)
-    for (const std::pair<Function *, NotInlinedProfileInfo> &pair :
-         notInlinedCallInfo)
-      updateProfileCallee(pair.first, pair.second.entryCount);
+    for (const auto &[Fn, Info] : notInlinedCallInfo)
+      updateProfileCallee(Fn, Info.entryCount);
 
   if (RemoveProbeAfterProfileAnnotation &&
       FunctionSamples::ProfileIsProbeBased) {

llvm/lib/Transforms/Scalar/GVNHoist.cpp

@@ -835,7 +835,7 @@ void GVNHoist::findHoistableCandidates(OutValuesType &CHIBBs,
 
   // CHIArgs now have the outgoing values, so check for anticipability and
   // accumulate hoistable candidates in HPL.
-  for (std::pair<BasicBlock *, SmallVector<CHIArg, 2>> &A : CHIBBs) {
+  for (auto &A : CHIBBs) {
     BasicBlock *BB = A.first;
     SmallVectorImpl<CHIArg> &CHIs = A.second;
     // Vector of PHIs contains PHIs for different instructions.