diff --git a/llvm/lib/Target/AArch64/AArch64SystemOperands.td b/llvm/lib/Target/AArch64/AArch64SystemOperands.td
--- a/llvm/lib/Target/AArch64/AArch64SystemOperands.td
+++ b/llvm/lib/Target/AArch64/AArch64SystemOperands.td
@@ -612,6 +612,7 @@
 def : ROSysReg<"CNTPCT_EL0",         0b11, 0b011, 0b1110, 0b0000, 0b001>;
 def : ROSysReg<"CNTVCT_EL0",         0b11, 0b011, 0b1110, 0b0000, 0b010>;
 def : ROSysReg<"ID_MMFR4_EL1",       0b11, 0b000, 0b0000, 0b0010, 0b110>;
+def : ROSysReg<"ID_MMFR5_EL1",       0b11, 0b000, 0b0000, 0b0011, 0b110>;
 
 // Trace registers
 //                                 Op0    Op1     CRn     CRm    Op2
diff --git a/llvm/test/MC/AArch64/basic-a64-diagnostics.s b/llvm/test/MC/AArch64/basic-a64-diagnostics.s
--- a/llvm/test/MC/AArch64/basic-a64-diagnostics.s
+++ b/llvm/test/MC/AArch64/basic-a64-diagnostics.s
@@ -3581,6 +3581,7 @@
         msr ID_MMFR2_EL1, x12
         msr ID_MMFR3_EL1, x12
         msr ID_MMFR4_EL1, x12
+        msr ID_MMFR5_EL1, x12
         msr ID_ISAR0_EL1, x12
         msr ID_ISAR1_EL1, x12
         msr ID_ISAR2_EL1, x12
@@ -3680,6 +3681,9 @@
 // CHECK-ERROR-NEXT:         msr ID_MMFR4_EL1, x12
 // CHECK-ERROR-NEXT:             ^
 // CHECK-ERROR-NEXT: error: expected writable system register or pstate
+// CHECK-ERROR-NEXT:         msr ID_MMFR5_EL1, x12
+// CHECK-ERROR-NEXT:             ^
+// CHECK-ERROR-NEXT: error: expected writable system register or pstate
 // CHECK-ERROR-NEXT:         msr ID_ISAR0_EL1, x12
 // CHECK-ERROR-NEXT:             ^
 // CHECK-ERROR-NEXT: error: expected writable system register or pstate
diff --git a/llvm/test/MC/AArch64/basic-a64-instructions.s b/llvm/test/MC/AArch64/basic-a64-instructions.s
--- a/llvm/test/MC/AArch64/basic-a64-instructions.s
+++ b/llvm/test/MC/AArch64/basic-a64-instructions.s
@@ -4295,6 +4295,7 @@
 	mrs x9, ID_MMFR2_EL1
 	mrs x9, ID_MMFR3_EL1
 	mrs x9, ID_MMFR4_EL1
+	mrs x9, ID_MMFR5_EL1
 	mrs x9, ID_ISAR0_EL1
 	mrs x9, ID_ISAR1_EL1
 	mrs x9, ID_ISAR2_EL1
@@ -4596,6 +4597,7 @@
 // CHECK: mrs      x9, {{id_mmfr2_el1|ID_MMFR2_EL1}}           // encoding: [0xc9,0x01,0x38,0xd5]
 // CHECK: mrs      x9, {{id_mmfr3_el1|ID_MMFR3_EL1}}           // encoding: [0xe9,0x01,0x38,0xd5]
 // CHECK: mrs      x9, {{id_mmfr4_el1|ID_MMFR4_EL1}}           // encoding: [0xc9,0x02,0x38,0xd5]
+// CHECK: mrs      x9, {{id_mmfr5_el1|ID_MMFR5_EL1}}           // encoding: [0xc9,0x03,0x38,0xd5]
 // CHECK: mrs      x9, {{id_isar0_el1|ID_ISAR0_EL1}}           // encoding: [0x09,0x02,0x38,0xd5]
 // CHECK: mrs      x9, {{id_isar1_el1|ID_ISAR1_EL1}}           // encoding: [0x29,0x02,0x38,0xd5]
 // CHECK: mrs      x9, {{id_isar2_el1|ID_ISAR2_EL1}}           // encoding: [0x49,0x02,0x38,0xd5]
diff --git a/llvm/test/MC/Disassembler/AArch64/basic-a64-instructions.txt b/llvm/test/MC/Disassembler/AArch64/basic-a64-instructions.txt
--- a/llvm/test/MC/Disassembler/AArch64/basic-a64-instructions.txt
+++ b/llvm/test/MC/Disassembler/AArch64/basic-a64-instructions.txt
@@ -3513,6 +3513,7 @@
 # CHECK: mrs      x9, {{id_mmfr2_el1|ID_MMFR2_EL1}}
 # CHECK: mrs      x9, {{id_mmfr3_el1|ID_MMFR3_EL1}}
 # CHECK: mrs      x9, {{id_mmfr4_el1|ID_MMFR4_EL1}}
+# CHECK: mrs      x9, {{id_mmfr5_el1|ID_MMFR5_EL1}}
 # CHECK: mrs      x9, {{id_isar0_el1|ID_ISAR0_EL1}}
 # CHECK: mrs      x9, {{id_isar1_el1|ID_ISAR1_EL1}}
 # CHECK: mrs      x9, {{id_isar2_el1|ID_ISAR2_EL1}}
@@ -4069,6 +4070,7 @@
 0xc9 0x1 0x38 0xd5
 0xe9 0x1 0x38 0xd5
 0xc9 0x2 0x38 0xd5
+0xc9 0x3 0x38 0xd5
 0x9 0x2 0x38 0xd5
 0x29 0x2 0x38 0xd5
 0x49 0x2 0x38 0xd5