[RISCV] Add srmcfg CSR from Ssqosid extension. (#79914)

Based on the spec here
https://github.com/riscv/riscv-ssqosid/releases/tag/v1.0-rc1

Ssqosid extension name will be added in a separate patch.

Author: topperc

llvm/lib/Target/RISCV/RISCVSystemOperands.td

@@ -132,6 +132,11 @@ def : SysReg<"sip", 0x144>;
 let DeprecatedName = "sptbr" in
 def : SysReg<"satp", 0x180>;
 
+//===----------------------------------------------------------------------===//
+// Quality-of-Service(QoS) Identifiers (Ssqosid)
+//===----------------------------------------------------------------------===//
+def : SysReg<"srmcfg", 0x181>;
+
 //===----------------------------------------------------------------------===//
 // Debug/Trace Registers
 //===----------------------------------------------------------------------===//

llvm/test/MC/RISCV/supervisor-csr-names.s

@@ -196,6 +196,24 @@ csrrs t1, satp, zero
 # uimm12
 csrrs t2, 0x180, zero
 
+#########################################
+# Quality-of-Service(QoS) Identifiers
+#########################################
+
+# srmcfg
+# name
+# CHECK-INST: csrrs t1, srmcfg, zero
+# CHECK-ENC: encoding: [0x73,0x23,0x10,0x18]
+# CHECK-INST-ALIAS: csrr t1, srmcfg
+# uimm12
+# CHECK-INST: csrrs t2, srmcfg, zero
+# CHECK-ENC: encoding: [0xf3,0x23,0x10,0x18]
+# CHECK-INST-ALIAS: csrr t2, srmcfg
+# name
+csrrs t1, srmcfg, zero
+# uimm12
+csrrs t2, 0x181, zero
+
 #########################################
 # Debug/Trace Registers
 #########################################