Index: clang/test/Driver/aarch64-perfmon.c
===================================================================
--- /dev/null
+++ clang/test/Driver/aarch64-perfmon.c
@@ -0,0 +1,13 @@
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.4a+pmuv3 %s 2>&1 | FileCheck --check-prefix=CHECK-PERFMON %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.2a+pmuv3 %s 2>&1 | FileCheck --check-prefix=CHECK-PERFMON %s
+// CHECK-PERFMON: "-target-feature" "+perfmon"
+
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.4a+nopmuv3 %s 2>&1 | FileCheck --check-prefix=CHECK-NOPERFMON %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.2a+nopmuv3 %s 2>&1 | FileCheck --check-prefix=CHECK-NOPERFMON %s
+// CHECK-NOPERFMON: "-target-feature" "-perfmon"
+
+// RUN: %clang -### -target aarch64-none-none-eabi                 %s 2>&1 | FileCheck %s --check-prefix=ABSENTPERFMON
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.4a %s 2>&1 | FileCheck %s --check-prefix=ABSENTPERFMON
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.2a %s 2>&1 | FileCheck %s --check-prefix=ABSENTPERFMON
+// ABSENTPERFMON-NOT: "-target-feature" "+perfmon"
+// ABSENTPERFMON-NOT: "-target-feature" "-perfmon"
\ No newline at end of file
Index: llvm/include/llvm/Support/AArch64TargetParser.h
===================================================================
--- llvm/include/llvm/Support/AArch64TargetParser.h
+++ llvm/include/llvm/Support/AArch64TargetParser.h
@@ -71,6 +71,7 @@
   AEK_SMEI64 =      1ULL << 39,
   AEK_HBC =         1ULL << 40,
   AEK_MOPS =        1ULL << 41,
+  AEK_PERFMON =     1ULL << 42,
 };
 
 enum class ArchKind {
Index: llvm/include/llvm/Support/AArch64TargetParser.def
===================================================================
--- llvm/include/llvm/Support/AArch64TargetParser.def
+++ llvm/include/llvm/Support/AArch64TargetParser.def
@@ -146,6 +146,7 @@
 AARCH64_ARCH_EXT_NAME("sme-i64",      AArch64::AEK_SMEI64,      "+sme-i64",      "-sme-i64")
 AARCH64_ARCH_EXT_NAME("hbc",          AArch64::AEK_HBC,         "+hbc",          "-hbc")
 AARCH64_ARCH_EXT_NAME("mops",         AArch64::AEK_MOPS,        "+mops",         "-mops")
+AARCH64_ARCH_EXT_NAME("pmuv3",        AArch64::AEK_PERFMON,     "+perfmon",      "-perfmon")
 #undef AARCH64_ARCH_EXT_NAME
 
 #ifndef AARCH64_CPU_NAME
Index: llvm/lib/Support/AArch64TargetParser.cpp
===================================================================
--- llvm/lib/Support/AArch64TargetParser.cpp
+++ llvm/lib/Support/AArch64TargetParser.cpp
@@ -118,6 +118,8 @@
     Features.push_back("+hbc");
   if (Extensions & AArch64::AEK_MOPS)
     Features.push_back("+mops");
+  if (Extensions & AArch64::AEK_PERFMON)
+    Features.push_back("+perfmon");
 
   return true;
 }
Index: llvm/unittests/Support/TargetParserTest.cpp
===================================================================
--- llvm/unittests/Support/TargetParserTest.cpp
+++ llvm/unittests/Support/TargetParserTest.cpp
@@ -1428,17 +1428,14 @@
 
 TEST(TargetParserTest, AArch64ExtensionFeatures) {
   std::vector<uint64_t> Extensions = {
-    AArch64::AEK_CRC,      AArch64::AEK_CRYPTO,
-    AArch64::AEK_FP,       AArch64::AEK_SIMD,
-    AArch64::AEK_FP16,     AArch64::AEK_PROFILE,
-    AArch64::AEK_RAS,      AArch64::AEK_LSE,
-    AArch64::AEK_RDM,      AArch64::AEK_DOTPROD,
-    AArch64::AEK_SVE,      AArch64::AEK_SVE2,
-    AArch64::AEK_SVE2AES,  AArch64::AEK_SVE2SM4,
-    AArch64::AEK_SVE2SHA3, AArch64::AEK_SVE2BITPERM,
-    AArch64::AEK_RCPC,     AArch64::AEK_FP16FML,
-    AArch64::AEK_SME,      AArch64::AEK_SMEF64,
-    AArch64::AEK_SMEI64 };
+      AArch64::AEK_CRC,         AArch64::AEK_CRYPTO,  AArch64::AEK_FP,
+      AArch64::AEK_SIMD,        AArch64::AEK_FP16,    AArch64::AEK_PROFILE,
+      AArch64::AEK_RAS,         AArch64::AEK_LSE,     AArch64::AEK_RDM,
+      AArch64::AEK_DOTPROD,     AArch64::AEK_SVE,     AArch64::AEK_SVE2,
+      AArch64::AEK_SVE2AES,     AArch64::AEK_SVE2SM4, AArch64::AEK_SVE2SHA3,
+      AArch64::AEK_SVE2BITPERM, AArch64::AEK_RCPC,    AArch64::AEK_FP16FML,
+      AArch64::AEK_SME,         AArch64::AEK_SMEF64,  AArch64::AEK_SMEI64,
+      AArch64::AEK_PERFMON};
 
   std::vector<StringRef> Features;
 
@@ -1473,6 +1470,7 @@
   EXPECT_TRUE(llvm::is_contained(Features, "+sme"));
   EXPECT_TRUE(llvm::is_contained(Features, "+sme-f64"));
   EXPECT_TRUE(llvm::is_contained(Features, "+sme-i64"));
+  EXPECT_TRUE(llvm::is_contained(Features, "+perfmon"));
 }
 
 TEST(TargetParserTest, AArch64ArchFeatures) {
@@ -1520,6 +1518,7 @@
       {"sme-i64", "nosme-i64", "+sme-i64", "-sme-i64"},
       {"hbc", "nohbc", "+hbc", "-hbc"},
       {"mops", "nomops", "+mops", "-mops"},
+      {"pmuv3", "nopmuv3", "+perfmon", "-perfmon"},
   };
 
   for (unsigned i = 0; i < array_lengthof(ArchExt); i++) {