Use llvm::less_first (NFC)

clang/lib/Serialization/ASTWriter.cpp

@@ -3205,9 +3205,7 @@ void ASTWriter::WritePragmaDiagnosticMappings(const DiagnosticsEngine &Diag,
       }
 
       // Sort by diag::kind for deterministic output.
-      llvm::sort(Mappings, [](const auto &LHS, const auto &RHS) {
-        return LHS.first < RHS.first;
-      });
+      llvm::sort(Mappings, llvm::less_first());
 
       for (const auto &I : Mappings) {
         Record.push_back(I.first);

clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

@@ -259,9 +259,7 @@ static void canonicalizeDefines(PreprocessorOptions &PPOpts) {
     ++Index;
   }
 
-  llvm::stable_sort(SimpleNames, [](const MacroOpt &A, const MacroOpt &B) {
-    return A.first < B.first;
-  });
+  llvm::stable_sort(SimpleNames, llvm::less_first());
   // Keep the last instance of each macro name by going in reverse
   auto NewEnd = std::unique(
       SimpleNames.rbegin(), SimpleNames.rend(),

llvm/lib/MC/MCPseudoProbe.cpp

@@ -182,13 +182,10 @@ void MCPseudoProbeInlineTree::emit(MCObjectStreamer *MCOS,
   // Emit sorted descendant. InlineSite is unique for each pair, so there will
   // be no ordering of Inlinee based on MCPseudoProbeInlineTree*
   using InlineeType = std::pair<InlineSite, MCPseudoProbeInlineTree *>;
-  auto Comparer = [](const InlineeType &A, const InlineeType &B) {
-    return A.first < B.first;
-  };
   std::vector<InlineeType> Inlinees;
   for (const auto &Child : Children)
     Inlinees.emplace_back(Child.first, Child.second.get());
-  std::sort(Inlinees.begin(), Inlinees.end(), Comparer);
+  llvm::sort(Inlinees, llvm::less_first());
 
   for (const auto &Inlinee : Inlinees) {
     // Emit probe index
@@ -230,13 +227,10 @@ void MCPseudoProbeSections::emit(MCObjectStreamer *MCOS) {
       // Emit sorted descendant. InlineSite is unique for each pair, so there
       // will be no ordering of Inlinee based on MCPseudoProbeInlineTree*
       using InlineeType = std::pair<InlineSite, MCPseudoProbeInlineTree *>;
-      auto Comparer = [](const InlineeType &A, const InlineeType &B) {
-        return A.first < B.first;
-      };
       std::vector<InlineeType> Inlinees;
       for (const auto &Child : Root.getChildren())
         Inlinees.emplace_back(Child.first, Child.second.get());
-      std::sort(Inlinees.begin(), Inlinees.end(), Comparer);
+      llvm::sort(Inlinees, llvm::less_first());
 
       for (const auto &Inlinee : Inlinees) {
         // Emit the group guarded by a sentinel probe.

llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.h

@@ -597,10 +597,7 @@ class SIMachineFunctionInfo final : public AMDGPUMachineFunction,
   const ReservedRegSet &getWWMReservedRegs() const { return WWMReservedRegs; }
 
   ArrayRef<PrologEpilogSGPRSpill> getPrologEpilogSGPRSpills() const {
-    assert(
-        is_sorted(PrologEpilogSGPRSpills, [](const auto &LHS, const auto &RHS) {
-          return LHS.first < RHS.first;
-        }));
+    assert(is_sorted(PrologEpilogSGPRSpills, llvm::less_first()));
     return PrologEpilogSGPRSpills;
   }
 

mlir/lib/Dialect/SparseTensor/Transforms/SparseReinterpretMap.cpp

@@ -557,9 +557,7 @@ struct GenericOpScheduler : public OpRewritePattern<linalg::GenericOp> {
         unsigned lvl = llvm::cast<AffineDimExpr>(expr).getPosition();
         lvlSeq.push_back(std::make_pair(lvl, lvlSeq.size()));
       }
-      std::sort(lvlSeq.begin(), lvlSeq.end(), [](auto &lhs, auto &rhs) -> bool {
-        return lhs.first < rhs.first;
-      });
+      llvm::sort(lvlSeq, llvm::less_first());
       SmallVector<unsigned> perm =
           llvm::to_vector(llvm::make_second_range(lvlSeq));
       auto dimToLvl = AffineMap::getPermutationMap(perm, linalgOp.getContext());

mlir/lib/Dialect/SparseTensor/Transforms/Utils/LoopEmitter.cpp

@@ -184,8 +184,7 @@ void LoopEmitter::initialize(ValueRange ts, StringAttr loopTag, bool hasOutput,
       for (Level l = 0; l < lvlRank; l++) {
         std::vector<std::pair<LoopId, unsigned>> deps = dimGetter(tid, l);
         // Sort the loop by order.
-        std::sort(deps.begin(), deps.end(),
-                  [](auto &lhs, auto &rhs) { return lhs.first < rhs.first; });
+        llvm::sort(deps, llvm::less_first());
 
         dependentLvlMap[tid][l] = std::move(deps);
         unsigned depends = dependentLvlMap[tid][l].size();