Don't override subreg functions in targets without subregisters.

Some targets have no sub-registers at all. Use the TargetRegisterInfo
versions of composeSubRegIndices(), getSubClassWithSubReg(), and
getMatchingSuperRegClass() for those targets.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156075 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetRegisterInfo.h

@@ -421,7 +421,9 @@ public:
   /// TableGen will synthesize missing A sub-classes.
   virtual const TargetRegisterClass *
   getMatchingSuperRegClass(const TargetRegisterClass *A,
-                           const TargetRegisterClass *B, unsigned Idx) const =0;
+                           const TargetRegisterClass *B, unsigned Idx) const {
+    llvm_unreachable("Target has no sub-registers");
+  }
 
   /// getSubClassWithSubReg - Returns the largest legal sub-class of RC that
   /// supports the sub-register index Idx.
@@ -436,7 +438,10 @@ public:
   ///
   /// TableGen will synthesize missing RC sub-classes.
   virtual const TargetRegisterClass *
-  getSubClassWithSubReg(const TargetRegisterClass *RC, unsigned Idx) const =0;
+  getSubClassWithSubReg(const TargetRegisterClass *RC, unsigned Idx) const {
+    assert(Idx == 0 && "Target has no sub-registers");
+    return RC;
+  }
 
   /// composeSubRegIndices - Return the subregister index you get from composing
   /// two subregister indices.

utils/TableGen/RegisterInfoEmitter.cpp

@@ -672,14 +672,16 @@ RegisterInfoEmitter::runTargetHeader(raw_ostream &OS, CodeGenTarget &Target,
      << "  explicit " << ClassName
      << "(unsigned RA, unsigned D = 0, unsigned E = 0);\n"
      << "  virtual bool needsStackRealignment(const MachineFunction &) const\n"
-     << "     { return false; }\n"
+     << "     { return false; }\n";
-     << "  unsigned composeSubRegIndices(unsigned, unsigned) const;\n"
+  if (!RegBank.getSubRegIndices().empty()) {
+    OS << "  unsigned composeSubRegIndices(unsigned, unsigned) const;\n"
       << "  const TargetRegisterClass *"
       "getSubClassWithSubReg(const TargetRegisterClass*, unsigned) const;\n"
       << "  const TargetRegisterClass *getMatchingSuperRegClass("
       "const TargetRegisterClass*, const TargetRegisterClass*, "
-        "unsigned) const;\n"
+      "unsigned) const;\n";
-     << "  const RegClassWeight &getRegClassWeight("
+  }
+  OS << "  const RegClassWeight &getRegClassWeight("
      << "const TargetRegisterClass *RC) const;\n"
      << "  unsigned getNumRegPressureSets() const;\n"
      << "  const char *getRegPressureSetName(unsigned Idx) const;\n"
@@ -945,6 +947,7 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
   std::string ClassName = Target.getName() + "GenRegisterInfo";
 
   // Emit composeSubRegIndices
+  if (!SubRegIndices.empty()) {
     OS << "unsigned " << ClassName
       << "::composeSubRegIndices(unsigned IdxA, unsigned IdxB) const {\n"
       << "  switch (IdxA) {\n"
@@ -967,15 +970,13 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
         OS << "    }\n";
     }
     OS << "  }\n}\n\n";
+  }
 
   // Emit getSubClassWithSubReg.
+  if (!SubRegIndices.empty()) {
     OS << "const TargetRegisterClass *" << ClassName
        << "::getSubClassWithSubReg(const TargetRegisterClass *RC, unsigned Idx)"
-        " const {\n";
+       << " const {\n";
-  if (SubRegIndices.empty()) {
-    OS << "  assert(Idx == 0 && \"Target has no sub-registers\");\n"
-       << "  return RC;\n";
-  } else {
     // Use the smallest type that can hold a regclass ID with room for a
     // sentinel.
     if (RegisterClasses.size() < UINT8_MAX)
@@ -1002,17 +1003,14 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
        << "  if (!Idx) return RC;\n  --Idx;\n"
        << "  assert(Idx < " << SubRegIndices.size() << " && \"Bad subreg\");\n"
        << "  unsigned TV = Table[RC->getID()][Idx];\n"
-       << "  return TV ? getRegClass(TV - 1) : 0;\n";
+       << "  return TV ? getRegClass(TV - 1) : 0;\n}\n\n";
   }
-  OS << "}\n\n";
 
   // Emit getMatchingSuperRegClass.
+  if (!SubRegIndices.empty()) {
     OS << "const TargetRegisterClass *" << ClassName
        << "::getMatchingSuperRegClass(const TargetRegisterClass *A,"
-        " const TargetRegisterClass *B, unsigned Idx) const {\n";
+       << " const TargetRegisterClass *B, unsigned Idx) const {\n";
-  if (SubRegIndices.empty()) {
-    OS << "  llvm_unreachable(\"Target has no sub-registers\");\n";
-  } else {
     // We need to find the largest sub-class of A such that every register has
     // an Idx sub-register in B.  Map (B, Idx) to a bit-vector of
     // super-register classes that map into B. Then compute the largest common
@@ -1047,9 +1045,8 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
        << "  for (unsigned i = 0; i != " << BVWords << "; ++i)\n"
        << "    if (unsigned Common = TV[i] & SC[i])\n"
        << "      return getRegClass(32*i + CountTrailingZeros_32(Common));\n"
-       << "  return 0;\n";
+       << "  return 0;\n}\n\n";
   }
-  OS << "}\n\n";
 
   EmitRegUnitPressure(OS, RegBank, ClassName);