[RISCV] Enable framework to resolve encoding conflicts among vendor-specific CSRs (llvm#97287)

This PR is a follow-up of PR llvm#96174 which added the framework to resolve
encoding conflicts among vendor specific CSRs. This PR explicitly
enables this only for the RISCV target.

Author: quic-garvgupt

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

@@ -1890,11 +1890,18 @@ ParseStatus RISCVAsmParser::parseCSRSystemRegister(OperandVector &Operands) {
     if (CE) {
       int64_t Imm = CE->getValue();
       if (isUInt<12>(Imm)) {
-        auto SysReg = RISCVSysReg::lookupSysRegByEncoding(Imm);
-        // Accept an immediate representing a named or un-named Sys Reg
-        // if the range is valid, regardless of the required features.
-        Operands.push_back(
-            RISCVOperand::createSysReg(SysReg ? SysReg->Name : "", S, Imm));
+        auto Range = RISCVSysReg::lookupSysRegByEncoding(Imm);
+        // Accept an immediate representing a named Sys Reg if it satisfies the
+        // the required features.
+        for (auto &Reg : Range) {
+          if (Reg.haveRequiredFeatures(STI->getFeatureBits())) {
+            Operands.push_back(RISCVOperand::createSysReg(Reg.Name, S, Imm));
+            return ParseStatus::Success;
+          }
+        }
+        // Accept an immediate representing an un-named Sys Reg if the range is
+        // valid, regardless of the required features.
+        Operands.push_back(RISCVOperand::createSysReg("", S, Imm));
         return ParseStatus::Success;
       }
     }

llvm/lib/Target/RISCV/MCTargetDesc/RISCVInstPrinter.cpp

@@ -121,11 +121,14 @@ void RISCVInstPrinter::printCSRSystemRegister(const MCInst *MI, unsigned OpNo,
                                               const MCSubtargetInfo &STI,
                                               raw_ostream &O) {
   unsigned Imm = MI->getOperand(OpNo).getImm();
-  auto SysReg = RISCVSysReg::lookupSysRegByEncoding(Imm);
-  if (SysReg && SysReg->haveRequiredFeatures(STI.getFeatureBits()))
-    markup(O, Markup::Register) << SysReg->Name;
-  else
-    markup(O, Markup::Register) << formatImm(Imm);
+  auto Range = RISCVSysReg::lookupSysRegByEncoding(Imm);
+  for (auto &Reg : Range) {
+    if (Reg.haveRequiredFeatures(STI.getFeatureBits())) {
+      markup(O, Markup::Register) << Reg.Name;
+      return;
+    }
+  }
+  markup(O, Markup::Register) << formatImm(Imm);
 }
 
 void RISCVInstPrinter::printFenceArg(const MCInst *MI, unsigned OpNo,

llvm/lib/Target/RISCV/RISCVSystemOperands.td

@@ -49,6 +49,7 @@ def SysRegsList : GenericTable {
 
   let PrimaryKey = [ "Encoding" ];
   let PrimaryKeyName = "lookupSysRegByEncoding";
+  let PrimaryKeyReturnRange = true;
 }
 
 def lookupSysRegByName : SearchIndex {