TableGen'erate mapping physical registers to encoding values.

Many targets always use the same bitwise encoding value for physical
registers in all (or most) instructions. Add this mapping to the
.td files and TableGen'erate the information and expose an accessor
in MCRegisterInfo.

patch by Tom Stellard.

llvm-svn: 156829

llvm/include/llvm/MC/MCRegisterInfo.h

@@ -146,6 +146,8 @@ private:
   const uint16_t *SubRegIndices;              // Pointer to the subreg lookup
                                               // array.
   unsigned NumSubRegIndices;                  // Number of subreg indices.
+  const uint16_t *RegEncodingTable;           // Pointer to array of register
+                                              // encodings.
 
   unsigned L2DwarfRegsSize;
   unsigned EHL2DwarfRegsSize;
@@ -164,7 +166,8 @@ public:
                           const MCRegisterClass *C, unsigned NC,
                           const uint16_t *RL,
                           const uint16_t *SubIndices,
-                          unsigned NumIndices) {
+                          unsigned NumIndices,
+                          const uint16_t *RET) {
     Desc = D;
     NumRegs = NR;
     RAReg = RA;
@@ -173,6 +176,7 @@ public:
     NumClasses = NC;
     SubRegIndices = SubIndices;
     NumSubRegIndices = NumIndices;
+    RegEncodingTable = RET;
   }
 
   /// mapLLVMRegsToDwarfRegs - Used to initialize LLVM register to Dwarf
@@ -354,6 +358,14 @@ public:
     assert(i < getNumRegClasses() && "Register Class ID out of range");
     return Classes[i];
   }
+
+   /// getEncodingValue - Returns the encoding for RegNo
+  uint16_t getEncodingValue(unsigned RegNo) const {
+    assert(RegNo < NumRegs &&
+           "Attempting to get encoding for invalid register number!");
+    return RegEncodingTable[RegNo];
+  }
+
 };
 
 } // End llvm namespace

llvm/include/llvm/Target/Target.td

@@ -96,6 +96,9 @@ class Register<string n, list<string> altNames = []> {
   // x86 register AX is covered by its sub-registers AL and AH, but EAX is not
   // covered by its sub-register AX.
   bit CoveredBySubRegs = 0;
+
+  // HWEncoding - The target specific hardware encoding for this register.
+  bits<16> HWEncoding = 0;
 }
 
 // RegisterWithSubRegs - This can be used to define instances of Register which

llvm/utils/TableGen/RegisterInfoEmitter.cpp

@@ -636,6 +636,23 @@ RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
 
   EmitRegMappingTables(OS, Regs, false);
 
+  // Emit Reg encoding table
+  OS << "extern const uint16_t " << TargetName;
+  OS << "RegEncodingTable[] = {\n";
+  // Add entry for NoRegister
+  OS << "  0,\n";
+  for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
+    Record *Reg = Regs[i]->TheDef;
+    BitsInit *BI = Reg->getValueAsBitsInit("HWEncoding");
+    uint64_t Value = 0;
+    for (unsigned b = 0, be = BI->getNumBits(); b != be; ++b) {
+      if (BitInit *B = dynamic_cast<BitInit*>(BI->getBit(b)))
+      Value |= (uint64_t)B->getValue() << b;
+    }
+    OS << "  " << Value << ",\n";
+  }
+  OS << "};\n";       // End of HW encoding table
+
   // MCRegisterInfo initialization routine.
   OS << "static inline void Init" << TargetName
      << "MCRegisterInfo(MCRegisterInfo *RI, unsigned RA, "
@@ -645,9 +662,11 @@ RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
      << RegisterClasses.size() << ", " << TargetName << "RegLists, ";
   if (SubRegIndices.size() != 0)
     OS << "(uint16_t*)" << TargetName << "SubRegTable, "
-       << SubRegIndices.size() << ");\n\n";
+       << SubRegIndices.size() << ",\n";
   else
-    OS << "NULL, 0);\n\n";
+    OS << "NULL, 0,\n";
+
+  OS << "  " << TargetName << "RegEncodingTable);\n\n";
 
   EmitRegMapping(OS, Regs, false);
 
@@ -1001,6 +1020,7 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
   if (SubRegIndices.size() != 0)
     OS << "extern const uint16_t *get" << TargetName
        << "SubRegTable();\n";
+  OS << "extern const uint16_t " << TargetName << "RegEncodingTable[];\n";
 
   EmitRegMappingTables(OS, Regs, true);
 
@@ -1016,9 +1036,11 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
      << "                     ";
   if (SubRegIndices.size() != 0)
     OS << "get" << TargetName << "SubRegTable(), "
-       << SubRegIndices.size() << ");\n\n";
+       << SubRegIndices.size() << ",\n";
   else
-    OS << "NULL, 0);\n\n";
+    OS << "NULL, 0,\n";
+
+  OS << "                     " << TargetName << "RegEncodingTable);\n\n";
 
   EmitRegMapping(OS, Regs, true);