Revert "[Mips] Support "$sp" named register (#136821)"

This reverts commit 13012fe.

Author: wzssyqa

llvm/lib/Target/Mips/MipsISelLowering.cpp

@@ -72,8 +72,6 @@
 #include <cstdint>
 #include <deque>
 #include <iterator>
-#include <regex>
-#include <string>
 #include <utility>
 #include <vector>
 
@@ -4867,101 +4865,25 @@ MipsTargetLowering::emitPseudoD_SELECT(MachineInstr &MI,
   return BB;
 }
 
-// Copies the function MipsAsmParser::matchCPURegisterName.
-int MipsTargetLowering::getCPURegisterIndex(StringRef Name) const {
-  int CC;
-
-  CC = StringSwitch<unsigned>(Name)
-           .Case("zero", 0)
-           .Case("at", 1)
-           .Case("AT", 1)
-           .Case("a0", 4)
-           .Case("a1", 5)
-           .Case("a2", 6)
-           .Case("a3", 7)
-           .Case("v0", 2)
-           .Case("v1", 3)
-           .Case("s0", 16)
-           .Case("s1", 17)
-           .Case("s2", 18)
-           .Case("s3", 19)
-           .Case("s4", 20)
-           .Case("s5", 21)
-           .Case("s6", 22)
-           .Case("s7", 23)
-           .Case("k0", 26)
-           .Case("k1", 27)
-           .Case("gp", 28)
-           .Case("sp", 29)
-           .Case("fp", 30)
-           .Case("s8", 30)
-           .Case("ra", 31)
-           .Case("t0", 8)
-           .Case("t1", 9)
-           .Case("t2", 10)
-           .Case("t3", 11)
-           .Case("t4", 12)
-           .Case("t5", 13)
-           .Case("t6", 14)
-           .Case("t7", 15)
-           .Case("t8", 24)
-           .Case("t9", 25)
-           .Default(-1);
-
-  if (!(ABI.IsN32() || ABI.IsN64()))
-    return CC;
-
-  // Although SGI documentation just cuts out t0-t3 for n32/n64,
-  // GNU pushes the values of t0-t3 to override the o32/o64 values for t4-t7
-  // We are supporting both cases, so for t0-t3 we'll just push them to t4-t7.
-  if (8 <= CC && CC <= 11)
-    CC += 4;
-
-  if (CC == -1)
-    CC = StringSwitch<unsigned>(Name)
-             .Case("a4", 8)
-             .Case("a5", 9)
-             .Case("a6", 10)
-             .Case("a7", 11)
-             .Case("kt0", 26)
-             .Case("kt1", 27)
-             .Default(-1);
-
-  return CC;
-}
-
 // FIXME? Maybe this could be a TableGen attribute on some registers and
 // this table could be generated automatically from RegInfo.
 Register
 MipsTargetLowering::getRegisterByName(const char *RegName, LLT VT,
                                       const MachineFunction &MF) const {
-  // 1. Delete symbol '$'.
-  std::string newRegName = RegName;
-  if (StringRef(RegName).starts_with("$"))
-    newRegName = StringRef(RegName).substr(1);
-
-  // 2. Get register index value.
-  std::smatch matchResult;
-  int regIdx;
-  static const std::regex matchStr("^[0-9]*$");
-  if (std::regex_match(newRegName, matchResult, matchStr))
-    regIdx = std::stoi(newRegName);
-  else {
-    newRegName = StringRef(newRegName).lower();
-    regIdx = getCPURegisterIndex(StringRef(newRegName));
-  }
-
-  // 3. Get register.
-  if (regIdx >= 0 && regIdx < 32) {
-    const MCRegisterInfo *MRI = MF.getContext().getRegisterInfo();
-    const MCRegisterClass &RC = Subtarget.isGP64bit()
-                                    ? MRI->getRegClass(Mips::GPR64RegClassID)
-                                    : MRI->getRegClass(Mips::GPR32RegClassID);
-    return RC.getRegister(regIdx);
+  // The Linux kernel uses $28 and sp.
+  if (Subtarget.isGP64bit()) {
+    Register Reg = StringSwitch<Register>(RegName)
+                       .Case("$28", Mips::GP_64)
+                       .Case("sp", Mips::SP_64)
+                       .Default(Register());
+    return Reg;
   }
 
-  report_fatal_error(
-      Twine("Invalid register name \"" + StringRef(RegName) + "\"."));
+  Register Reg = StringSwitch<Register>(RegName)
+                     .Case("$28", Mips::GP)
+                     .Case("sp", Mips::SP)
+                     .Default(Register());
+  return Reg;
 }
 
 MachineBasicBlock *MipsTargetLowering::emitLDR_W(MachineInstr &MI,

llvm/lib/Target/Mips/MipsISelLowering.h

@@ -505,8 +505,6 @@ class TargetRegisterClass;
       return true;
     }
 
-    int getCPURegisterIndex(StringRef Name) const;
-
     /// Emit a sign-extension using sll/sra, seb, or seh appropriately.
     MachineBasicBlock *emitSignExtendToI32InReg(MachineInstr &MI,
                                                 MachineBasicBlock *BB,