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+pmuv3p4 %s 2>&1 | FileCheck --check-prefix=CHECK-PERFMON %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.2a+pmuv3p4 %s 2>&1 | FileCheck --check-prefix=CHECK-PERFMON %s
+// CHECK-PERFMON: "-target-feature" "+perfmon"
+
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.4a+nopmuv3p4 %s 2>&1 | FileCheck --check-prefix=CHECK-NOPERFMON %s
+// RUN: %clang -### -target aarch64-none-none-eabi -march=armv8.2a+nopmuv3p4 %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: clang/test/Driver/arm-perfmon.c
===================================================================
--- /dev/null
+++ clang/test/Driver/arm-perfmon.c
@@ -0,0 +1,13 @@
+// RUN: %clang -### -target arm-none-none-eabi -march=armv8.4a+pmuv3p4 %s 2>&1 | FileCheck --check-prefix=CHECK-PERFMON %s
+// RUN: %clang -### -target arm-none-none-eabi -march=armv8.2a+pmuv3p4 %s 2>&1 | FileCheck --check-prefix=CHECK-PERFMON %s
+// CHECK-PERFMON: "-target-feature" "+perfmon"
+
+// RUN: %clang -### -target arm-none-none-eabi -march=armv8.4a+nopmuv3p4 %s 2>&1 | FileCheck --check-prefix=CHECK-NOPERFMON %s
+// RUN: %clang -### -target arm-none-none-eabi -march=armv8.2a+nopmuv3p4 %s 2>&1 | FileCheck --check-prefix=CHECK-NOPERFMON %s
+// CHECK-NOPERFMON: "-target-feature" "-perfmon"
+
+// RUN: %clang -### -target arm-none-none-eabi                 %s 2>&1 | FileCheck %s --check-prefix=ABSENTPERFMON
+// RUN: %clang -### -target arm-none-none-eabi -march=armv8.4a %s 2>&1 | FileCheck %s --check-prefix=ABSENTPERFMON
+// RUN: %clang -### -target arm-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
@@ -69,6 +69,7 @@
   AEK_SME =         1ULL << 37,
   AEK_SMEF64 =      1ULL << 38,
   AEK_SMEI64 =      1ULL << 39,
+  AEK_PERFMON =     1ULL << 40,
 };
 
 enum class ArchKind {
Index: llvm/include/llvm/Support/AArch64TargetParser.def
===================================================================
--- llvm/include/llvm/Support/AArch64TargetParser.def
+++ llvm/include/llvm/Support/AArch64TargetParser.def
@@ -144,6 +144,7 @@
 AARCH64_ARCH_EXT_NAME("sme",          AArch64::AEK_SME,         "+sme",   "-sme")
 AARCH64_ARCH_EXT_NAME("sme-f64",      AArch64::AEK_SMEF64,      "+sme-f64", "-sme-f64")
 AARCH64_ARCH_EXT_NAME("sme-i64",      AArch64::AEK_SMEI64,      "+sme-i64", "-sme-i64")
+AARCH64_ARCH_EXT_NAME("pmuv3p4",      AArch64::AEK_PERFMON,     "+perfmon", "-perfmon")
 #undef AARCH64_ARCH_EXT_NAME
 
 #ifndef AARCH64_CPU_NAME
Index: llvm/include/llvm/Support/ARMTargetParser.h
===================================================================
--- llvm/include/llvm/Support/ARMTargetParser.h
+++ llvm/include/llvm/Support/ARMTargetParser.h
@@ -60,6 +60,7 @@
   AEK_CDECP6 =      1 << 28,
   AEK_CDECP7 =      1 << 29,
   AEK_PACBTI =      1 << 30,
+  AEK_PERFMON =     1ULL << 31,
   // Unsupported extensions.
   AEK_OS       =    1ULL << 59,
   AEK_IWMMXT   =    1ULL << 60,
Index: llvm/include/llvm/Support/ARMTargetParser.def
===================================================================
--- llvm/include/llvm/Support/ARMTargetParser.def
+++ llvm/include/llvm/Support/ARMTargetParser.def
@@ -213,6 +213,7 @@
 ARM_ARCH_EXT_NAME("cdecp6",   ARM::AEK_CDECP6,   "+cdecp6",  "-cdecp6")
 ARM_ARCH_EXT_NAME("cdecp7",   ARM::AEK_CDECP7,   "+cdecp7",  "-cdecp7")
 ARM_ARCH_EXT_NAME("pacbti",   ARM::AEK_PACBTI,   "+pacbti",  "-pacbti")
+ARM_ARCH_EXT_NAME("pmuv3p4",  ARM::AEK_PERFMON,  "+perfmon", "-perfmon")
 #undef ARM_ARCH_EXT_NAME
 
 #ifndef ARM_HW_DIV_NAME
Index: llvm/lib/Support/AArch64TargetParser.cpp
===================================================================
--- llvm/lib/Support/AArch64TargetParser.cpp
+++ llvm/lib/Support/AArch64TargetParser.cpp
@@ -114,6 +114,8 @@
     Features.push_back("+sme-f64");
   if (Extensions & AArch64::AEK_SMEI64)
     Features.push_back("+sme-i64");
+  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
@@ -728,7 +728,8 @@
                               {"sb", "nosb", "+sb", "-sb"},
                               {"i8mm", "noi8mm", "+i8mm", "-i8mm"},
                               {"mve", "nomve", "+mve", "-mve"},
-                              {"mve.fp", "nomve.fp", "+mve.fp", "-mve.fp"}};
+                              {"mve.fp", "nomve.fp", "+mve.fp", "-mve.fp"},
+                              {"pmuv3p4", "nopmuv3p4", "+perfmon", "-perfmon"}};
 
   for (unsigned i = 0; i < array_lengthof(ArchExt); i++) {
     EXPECT_EQ(StringRef(ArchExt[i][2]), ARM::getArchExtFeature(ArchExt[i][0]));
@@ -1438,7 +1439,7 @@
     AArch64::AEK_SVE2SHA3, AArch64::AEK_SVE2BITPERM,
     AArch64::AEK_RCPC,     AArch64::AEK_FP16FML,
     AArch64::AEK_SME,      AArch64::AEK_SMEF64,
-    AArch64::AEK_SMEI64 };
+    AArch64::AEK_SMEI64,   AArch64::AEK_PERFMON};
 
   std::vector<StringRef> Features;
 
@@ -1473,6 +1474,7 @@
   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) {
@@ -1521,6 +1523,7 @@
                               {"sme", "nosme", "+sme", "-sme"},
                               {"sme-f64", "nosme-f64", "+sme-f64", "-sme-f64"},
                               {"sme-i64", "nosme-i64", "+sme-i64", "-sme-i64"},
+                              {"pmuv3p4", "nopmuv3p4", "+perfmon", "-perfmon"},
 };
 
   for (unsigned i = 0; i < array_lengthof(ArchExt); i++) {