[AArch64] Use GenericTable PrimaryKey to remove one of the SearchIndexes for SysRegs. NFC (llvm#122001)

Use PrimaryKeyReturnRange to get all of the registers with the same
encoding. This allows AltName to be removed.

Author: topperc

llvm/lib/Target/AArch64/AArch64SystemOperands.td

@@ -998,7 +998,6 @@ defm : TLBI<"VMALLWS2E1OS",  0b100, 0b1000, 0b0101, 0b010, 0>;
 class SysReg<string name, bits<2> op0, bits<3> op1, bits<4> crn, bits<4> crm,
              bits<3> op2> {
   string Name = name;
-  string AltName = name;
   bits<16> Encoding;
   let Encoding{15-14} = op0;
   let Encoding{13-11} = op1;
@@ -1018,20 +1017,18 @@ def SysRegValues : GenericEnum {
 
 def SysRegsList : GenericTable {
   let FilterClass = "SysReg";
-  let Fields = ["Name", "AltName", "Encoding", "Readable", "Writeable",
-                "Requires"];
+  let Fields = ["Name", "Encoding", "Readable", "Writeable", "Requires"];
+
+  let PrimaryKey = ["Encoding"];
+  let PrimaryKeyName = "lookupSysRegByEncoding";
+  let PrimaryKeyReturnRange = true;
 }
 
 def lookupSysRegByName : SearchIndex {
   let Table = SysRegsList;
   let Key = ["Name"];
 }
 
-def lookupSysRegByEncoding : SearchIndex {
-  let Table = SysRegsList;
-  let Key = ["Encoding"];
-}
-
 class RWSysReg<string name, bits<2> op0, bits<3> op1, bits<4> crn, bits<4> crm,
                bits<3> op2>
     : SysReg<name, op0, op1, crn, crm, op2> {
@@ -1317,9 +1314,7 @@ def : RWSysReg<"TTBR0_EL1",          0b11, 0b000, 0b0010, 0b0000, 0b000>;
 def : RWSysReg<"TTBR0_EL3",          0b11, 0b110, 0b0010, 0b0000, 0b000>;
 
 let Requires = [{ {AArch64::FeatureEL2VMSA} }] in {
-def : RWSysReg<"TTBR0_EL2",          0b11, 0b100, 0b0010, 0b0000, 0b000> {
-  let AltName = "VSCTLR_EL2";
-}
+def : RWSysReg<"TTBR0_EL2",          0b11, 0b100, 0b0010, 0b0000, 0b000>;
 def : RWSysReg<"VTTBR_EL2",          0b11, 0b100, 0b0010, 0b0001, 0b000>;
 }
 
@@ -1706,9 +1701,7 @@ def : RWSysReg<"ICH_LR15_EL2",       0b11, 0b100, 0b1100, 0b1101, 0b111>;
 let Requires = [{ {AArch64::HasV8_0rOps} }] in {
 //Virtualization System Control Register
 //                                 Op0   Op1    CRn     CRm     Op2
-def : RWSysReg<"VSCTLR_EL2",       0b11, 0b100, 0b0010, 0b0000, 0b000> {
-  let AltName = "TTBR0_EL2";
-}
+def : RWSysReg<"VSCTLR_EL2",       0b11, 0b100, 0b0010, 0b0000, 0b000>;
 
 //MPU Type Register
 //                                 Op0   Op1    CRn     CRm     Op2

llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp

@@ -1874,26 +1874,25 @@ void AArch64InstPrinter::printBarriernXSOption(const MCInst *MI, unsigned OpNo,
     markup(O, Markup::Immediate) << "#" << Val;
 }
 
-static bool isValidSysReg(const AArch64SysReg::SysReg *Reg, bool Read,
+static bool isValidSysReg(const AArch64SysReg::SysReg &Reg, bool Read,
                           const MCSubtargetInfo &STI) {
-  return (Reg && (Read ? Reg->Readable : Reg->Writeable) &&
-          Reg->haveFeatures(STI.getFeatureBits()));
+  return (Read ? Reg.Readable : Reg.Writeable) &&
+         Reg.haveFeatures(STI.getFeatureBits());
 }
 
-// Looks up a system register either by encoding or by name. Some system
+// Looks up a system register either by encoding. Some system
 // registers share the same encoding between different architectures,
-// therefore a tablegen lookup by encoding will return an entry regardless
-// of the register's predication on a specific subtarget feature. To work
-// around this problem we keep an alternative name for such registers and
-// look them up by that name if the first lookup was unsuccessful.
+// to work around this tablegen will return a range of registers with the same
+// encodings. We need to check each register in the range to see if it valid.
 static const AArch64SysReg::SysReg *lookupSysReg(unsigned Val, bool Read,
                                                  const MCSubtargetInfo &STI) {
-  const AArch64SysReg::SysReg *Reg = AArch64SysReg::lookupSysRegByEncoding(Val);
-
-  if (Reg && !isValidSysReg(Reg, Read, STI))
-    Reg = AArch64SysReg::lookupSysRegByName(Reg->AltName);
+  auto Range = AArch64SysReg::lookupSysRegByEncoding(Val);
+  for (auto &Reg : Range) {
+    if (isValidSysReg(Reg, Read, STI))
+      return &Reg;
+  }
 
-  return Reg;
+  return nullptr;
 }
 
 void AArch64InstPrinter::printMRSSystemRegister(const MCInst *MI, unsigned OpNo,
@@ -1917,7 +1916,7 @@ void AArch64InstPrinter::printMRSSystemRegister(const MCInst *MI, unsigned OpNo,
 
   const AArch64SysReg::SysReg *Reg = lookupSysReg(Val, true /*Read*/, STI);
 
-  if (isValidSysReg(Reg, true /*Read*/, STI))
+  if (Reg)
     O << Reg->Name;
   else
     O << AArch64SysReg::genericRegisterString(Val);
@@ -1944,7 +1943,7 @@ void AArch64InstPrinter::printMSRSystemRegister(const MCInst *MI, unsigned OpNo,
 
   const AArch64SysReg::SysReg *Reg = lookupSysReg(Val, false /*Read*/, STI);
 
-  if (isValidSysReg(Reg, false /*Read*/, STI))
+  if (Reg)
     O << Reg->Name;
   else
     O << AArch64SysReg::genericRegisterString(Val);

llvm/lib/Target/AArch64/Utils/AArch64BaseInfo.h

@@ -719,7 +719,6 @@ AArch64StringToVectorLayout(StringRef LayoutStr) {
 namespace AArch64SysReg {
   struct SysReg {
     const char Name[32];
-    const char AltName[32];
     unsigned Encoding;
     bool Readable;
     bool Writeable;
@@ -735,9 +734,6 @@ namespace AArch64SysReg {
 #define GET_SysRegValues_DECL
 #include "AArch64GenSystemOperands.inc"
 
-  const SysReg *lookupSysRegByName(StringRef);
-  const SysReg *lookupSysRegByEncoding(uint16_t);
-
   uint32_t parseGenericRegister(StringRef Name);
   std::string genericRegisterString(uint32_t Bits);
 }