diff --git a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
--- a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -3211,6 +3211,9 @@
     {"pauth", {AArch64::FeaturePAuth}},
     {"flagm", {AArch64::FeatureFlagM}},
     {"rme", {AArch64::FeatureRME}},
+    {"sme", {AArch64::FeatureSME}},
+    {"sme-f64", {AArch64::FeatureSMEF64}},
+    {"sme-i64", {AArch64::FeatureSMEI64}},
     // FIXME: Unsupported extensions
     {"lor", {}},
     {"rdma", {}},
diff --git a/llvm/test/MC/AArch64/SME/directives-negative.s b/llvm/test/MC/AArch64/SME/directives-negative.s
new file mode 100644
--- /dev/null
+++ b/llvm/test/MC/AArch64/SME/directives-negative.s
@@ -0,0 +1,37 @@
+// RUN: not llvm-mc -triple aarch64 -o - %s 2>&1 | FileCheck %s
+
+.arch_extension sme
+.arch_extension nosme
+smstart
+// CHECK: error: instruction requires: sme
+// CHECK-NEXT: smstart
+
+.arch_extension sme-f64
+.arch_extension nosme-f64
+fmopa za0.d, p0/m, p0/m, z0.d, z0.d
+// CHECK: error: instruction requires: sme-f64
+// CHECK-NEXT: fmopa za0.d, p0/m, p0/m, z0.d, z0.d
+
+.arch_extension sme-i64
+.arch_extension nosme-i64
+addha za0.d, p0/m, p0/m, z0.d
+// CHECK: error: instruction requires: sme-i64
+// CHECK-NEXT: addha za0.d, p0/m, p0/m, z0.d
+
+.arch armv8-a+sme
+.arch armv8-a+nosme
+smstart
+// CHECK: error: instruction requires: sme
+// CHECK-NEXT: smstart
+
+.arch armv8-a+sme-f64
+.arch armv8-a+nosme-f64
+fmopa za0.d, p0/m, p0/m, z0.d, z0.d
+// CHECK: error: instruction requires: sme-f64
+// CHECK-NEXT: fmopa za0.d, p0/m, p0/m, z0.d, z0.d
+
+.arch armv8-a+sme-i64
+.arch armv8-a+nosme-i64
+addha za0.d, p0/m, p0/m, z0.d
+// CHECK: error: instruction requires: sme-i64
+// CHECK-NEXT: addha za0.d, p0/m, p0/m, z0.d
diff --git a/llvm/test/MC/AArch64/SME/directives.s b/llvm/test/MC/AArch64/SME/directives.s
new file mode 100644
--- /dev/null
+++ b/llvm/test/MC/AArch64/SME/directives.s
@@ -0,0 +1,35 @@
+// RUN: llvm-mc -triple aarch64 -o - %s 2>&1 | FileCheck %s
+
+.arch_extension sme
+smstart
+// CHECK: smstart
+
+.arch_extension nosme
+
+.arch_extension sme-f64
+fmopa za0.d, p0/m, p0/m, z0.d, z0.d
+// CHECK: fmopa za0.d, p0/m, p0/m, z0.d, z0.d
+
+.arch_extension nosme-f64
+
+.arch_extension sme-i64
+addha za0.d, p0/m, p0/m, z0.d
+// CHECK: addha za0.d, p0/m, p0/m, z0.d
+
+.arch_extension nosme-i64
+
+.arch armv8-a+sme
+smstart
+// CHECK: smstart
+
+.arch armv8-a+nosme
+
+.arch armv8-a+sme-f64
+fmopa za0.d, p0/m, p0/m, z0.d, z0.d
+// CHECK: fmopa za0.d, p0/m, p0/m, z0.d, z0.d
+
+.arch armv8-a+nosme-f64
+
+.arch armv8-a+sme-i64
+addha za0.d, p0/m, p0/m, z0.d
+// CHECK: addha za0.d, p0/m, p0/m, z0.d