STLExtras: Provide less/equal functors with templated function call operators, plus a deref'ing functor template utility

Similar to the C++14 void specializations of these templates, useful as
a stop-gap until LLVM switches to '14.

Example use-cases in tblgen because I saw some functors that looked like
they could be simplified/refactored.

Reviewers: dexonsmith

Differential Revision: http://reviews.llvm.org/D7324

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227828 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/STLExtras.h

@@ -24,6 +24,7 @@
 #include <iterator>
 #include <memory>
 #include <utility> // for std::pair
+#include <cassert>
 
 namespace llvm {
 
@@ -558,6 +559,35 @@ struct pair_hash {
   }
 };
 
+/// A functor like C++14's std::less<void> in its absence.
+struct less {
+  template <typename A, typename B> bool operator()(A &&a, B &&b) const {
+    return std::forward<A>(a) < std::forward<B>(b);
+  }
+};
+
+/// A functor like C++14's std::equal<void> in its absence.
+struct equal {
+  template <typename A, typename B> bool operator()(A &&a, B &&b) const {
+    return std::forward<A>(a) == std::forward<B>(b);
+  }
+};
+
+/// Binary functor that adapts to any other binary functor after dereferencing
+/// operands.
+template <typename T> struct deref {
+  T func;
+  // Could be further improved to cope with non-derivable functors and
+  // non-binary functors (should be a variadic template member function
+  // operator()).
+  template <typename A, typename B>
+  auto operator()(A &lhs, B &rhs) const -> decltype(func(*lhs, *rhs)) {
+    assert(lhs);
+    assert(rhs);
+    return func(*lhs, *rhs);
+  }
+};
+
 } // End llvm namespace
 
 #endif

utils/TableGen/CodeGenRegisters.cpp

@@ -643,8 +643,8 @@ struct TupleExpander : SetTheory::Expander {
 //===----------------------------------------------------------------------===//
 
 static void sortAndUniqueRegisters(CodeGenRegister::Vec &M) {
-  std::sort(M.begin(), M.end(), CodeGenRegister::Less());
-  M.erase(std::unique(M.begin(), M.end(), CodeGenRegister::Equal()), M.end());
+  std::sort(M.begin(), M.end(), deref<llvm::less>());
+  M.erase(std::unique(M.begin(), M.end(), deref<llvm::equal>()), M.end());
 }
 
 CodeGenRegisterClass::CodeGenRegisterClass(CodeGenRegBank &RegBank, Record *R)
@@ -756,7 +756,7 @@ void CodeGenRegisterClass::inheritProperties(CodeGenRegBank &RegBank) {
 
 bool CodeGenRegisterClass::contains(const CodeGenRegister *Reg) const {
   return std::binary_search(Members.begin(), Members.end(), Reg,
-                            CodeGenRegister::Less());
+                            deref<llvm::less>());
 }
 
 namespace llvm {
@@ -789,10 +789,10 @@ operator<(const CodeGenRegisterClass::Key &B) const {
 static bool testSubClass(const CodeGenRegisterClass *A,
                          const CodeGenRegisterClass *B) {
   return A->SpillAlignment && B->SpillAlignment % A->SpillAlignment == 0 &&
-    A->SpillSize <= B->SpillSize &&
-    std::includes(A->getMembers().begin(), A->getMembers().end(),
-                  B->getMembers().begin(), B->getMembers().end(),
-                  CodeGenRegister::Less());
+         A->SpillSize <= B->SpillSize &&
+         std::includes(A->getMembers().begin(), A->getMembers().end(),
+                       B->getMembers().begin(), B->getMembers().end(),
+                       deref<llvm::less>());
 }
 
 /// Sorting predicate for register classes.  This provides a topological
@@ -1844,10 +1844,9 @@ void CodeGenRegBank::inferCommonSubClass(CodeGenRegisterClass *RC) {
     const CodeGenRegister::Vec &Memb1 = RC1->getMembers();
     const CodeGenRegister::Vec &Memb2 = RC2->getMembers();
     CodeGenRegister::Vec Intersection;
-    std::set_intersection(Memb1.begin(), Memb1.end(),
-                          Memb2.begin(), Memb2.end(),
-                          std::inserter(Intersection, Intersection.begin()),
-                          CodeGenRegister::Less());
+    std::set_intersection(
+        Memb1.begin(), Memb1.end(), Memb2.begin(), Memb2.end(),
+        std::inserter(Intersection, Intersection.begin()), deref<llvm::less>());
 
     // Skip disjoint class pairs.
     if (Intersection.empty())
@@ -1874,7 +1873,7 @@ void CodeGenRegBank::inferCommonSubClass(CodeGenRegisterClass *RC) {
 void CodeGenRegBank::inferSubClassWithSubReg(CodeGenRegisterClass *RC) {
   // Map SubRegIndex to set of registers in RC supporting that SubRegIndex.
   typedef std::map<const CodeGenSubRegIndex *, CodeGenRegister::Vec,
-                   CodeGenSubRegIndex::Less> SubReg2SetMap;
+                   deref<llvm::less>> SubReg2SetMap;
 
   // Compute the set of registers supporting each SubRegIndex.
   SubReg2SetMap SRSets;

utils/TableGen/CodeGenRegisters.h

@@ -73,17 +73,9 @@ namespace llvm {
     const std::string &getNamespace() const { return Namespace; }
     std::string getQualifiedName() const;
 
-    // Order CodeGenSubRegIndex pointers by EnumValue.
-    struct Less {
-      bool operator()(const CodeGenSubRegIndex *A,
-                      const CodeGenSubRegIndex *B) const {
-        assert(A && B);
-        return A->EnumValue < B->EnumValue;
-      }
-    };
-
     // Map of composite subreg indices.
-    typedef std::map<CodeGenSubRegIndex*, CodeGenSubRegIndex*, Less> CompMap;
+    typedef std::map<CodeGenSubRegIndex *, CodeGenSubRegIndex *,
+                     deref<llvm::less>> CompMap;
 
     // Returns the subreg index that results from composing this with Idx.
     // Returns NULL if this and Idx don't compose.
@@ -125,6 +117,11 @@ namespace llvm {
     CompMap Composed;
   };
 
+  inline bool operator<(const CodeGenSubRegIndex &A,
+                        const CodeGenSubRegIndex &B) {
+    return A.EnumValue < B.EnumValue;
+  }
+
   /// CodeGenRegister - Represents a register definition.
   struct CodeGenRegister {
     Record *TheDef;
@@ -133,8 +130,8 @@ namespace llvm {
     bool CoveredBySubRegs;
 
     // Map SubRegIndex -> Register.
-    typedef std::map<CodeGenSubRegIndex*, CodeGenRegister*,
-                     CodeGenSubRegIndex::Less> SubRegMap;
+    typedef std::map<CodeGenSubRegIndex *, CodeGenRegister *, deref<llvm::less>>
+        SubRegMap;
 
     CodeGenRegister(Record *R, unsigned Enum);
 
@@ -232,23 +229,6 @@ namespace llvm {
     // Get the sum of this register's register unit weights.
     unsigned getWeight(const CodeGenRegBank &RegBank) const;
 
-    // Order CodeGenRegister pointers by EnumValue.
-    struct Less {
-      bool operator()(const CodeGenRegister *A,
-                      const CodeGenRegister *B) const {
-        assert(A && B);
-        return A->EnumValue < B->EnumValue;
-      }
-    };
-
-    struct Equal {
-      bool operator()(const CodeGenRegister *A,
-                      const CodeGenRegister *B) const {
-        assert(A && B);
-        return A->EnumValue == B->EnumValue;
-      }
-    };
-
     // Canonically ordered set.
     typedef std::vector<const CodeGenRegister*> Vec;
 
@@ -274,6 +254,13 @@ namespace llvm {
     RegUnitLaneMaskList RegUnitLaneMasks;
   };
 
+  inline bool operator<(const CodeGenRegister &A, const CodeGenRegister &B) {
+    return A.EnumValue < B.EnumValue;
+  }
+
+  inline bool operator==(const CodeGenRegister &A, const CodeGenRegister &B) {
+    return A.EnumValue == B.EnumValue;
+  }
 
   class CodeGenRegisterClass {
     CodeGenRegister::Vec Members;

utils/TableGen/RegisterInfoEmitter.cpp

@@ -815,7 +815,7 @@ RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
   // Keep track of sub-register names as well. These are not differentially
   // encoded.
   typedef SmallVector<const CodeGenSubRegIndex*, 4> SubRegIdxVec;
-  SequenceToOffsetTable<SubRegIdxVec, CodeGenSubRegIndex::Less> SubRegIdxSeqs;
+  SequenceToOffsetTable<SubRegIdxVec, deref<llvm::less>> SubRegIdxSeqs;
   SmallVector<SubRegIdxVec, 4> SubRegIdxLists(Regs.size());
 
   SequenceToOffsetTable<std::string> RegStrings;
@@ -1205,7 +1205,7 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
     // Compress the sub-reg index lists.
     typedef std::vector<const CodeGenSubRegIndex*> IdxList;
     SmallVector<IdxList, 8> SuperRegIdxLists(RegisterClasses.size());
-    SequenceToOffsetTable<IdxList, CodeGenSubRegIndex::Less> SuperRegIdxSeqs;
+    SequenceToOffsetTable<IdxList, deref<llvm::less>> SuperRegIdxSeqs;
     BitVector MaskBV(RegisterClasses.size());
 
     for (const auto &RC : RegisterClasses) {