Index: clang/test/Preprocessor/riscv-target-features.c
===================================================================
--- clang/test/Preprocessor/riscv-target-features.c
+++ clang/test/Preprocessor/riscv-target-features.c
@@ -463,6 +463,14 @@
 // RUN: -o - | FileCheck --check-prefix=CHECK-ZICBOP-EXT %s
 // CHECK-ZICBOP-EXT: __riscv_zicbop 1000000{{$}}
 
+// RUN: %clang -target riscv32-unknown-linux-gnu -menable-experimental-extensions \
+// RUN: -march=rv32izawrs1p0 -x c -E -dM %s \
+// RUN: -o - | FileCheck --check-prefix=CHECK-ZAWRS-EXT %s
+// RUN: %clang -target riscv64-unknown-linux-gnu -menable-experimental-extensions \
+// RUN: -march=rv64izawrs1p0 -x c -E -dM %s \
+// RUN: -o - | FileCheck --check-prefix=CHECK-ZAWRS-EXT %s
+// CHECK-ZAWRS-EXT: __riscv_zawrs 1000000{{$}}
+
 // RUN: %clang -target riscv32-unknown-linux-gnu -menable-experimental-extensions \
 // RUN: -march=rv32iztso0p1 -x c -E -dM %s \
 // RUN: -o - | FileCheck --check-prefix=CHECK-ZTSO-EXT %s
Index: llvm/lib/Support/RISCVISAInfo.cpp
===================================================================
--- llvm/lib/Support/RISCVISAInfo.cpp
+++ llvm/lib/Support/RISCVISAInfo.cpp
@@ -114,6 +114,7 @@
     {"zbt", RISCVExtensionVersion{0, 93}},
     {"zca", RISCVExtensionVersion{0, 70}},
     {"zvfh", RISCVExtensionVersion{0, 1}},
+    {"zawrs", RISCVExtensionVersion{1, 0}},
     {"ztso", RISCVExtensionVersion{0, 1}},
 };
 
Index: llvm/lib/Target/RISCV/RISCV.td
===================================================================
--- llvm/lib/Target/RISCV/RISCV.td
+++ llvm/lib/Target/RISCV/RISCV.td
@@ -461,6 +461,13 @@
                            AssemblerPredicate<(all_of FeatureStdExtZtso),
                            "'Ztso' (Memory Model - Total Store Order)">;
 
+def FeatureStdExtZawrs
+    : SubtargetFeature<"experimental-zawrs", "HasStdExtZawrs", "true",
+                       "'Zawrs' (Wait on Reservation Set)">;
+def HasStdExtZawrs : Predicate<"Subtarget->hasStdExtZawrs()">,
+                           AssemblerPredicate<(all_of FeatureStdExtZawrs),
+                           "'Zawrs' (Wait on Reservation Set)">;
+
 // Feature32Bit exists to mark CPUs that support RV32 to distinquish them from
 // tuning CPU names.
 def Feature32Bit
Index: llvm/lib/Target/RISCV/RISCVInstrInfo.td
===================================================================
--- llvm/lib/Target/RISCV/RISCVInstrInfo.td
+++ llvm/lib/Target/RISCV/RISCVInstrInfo.td
@@ -705,6 +705,23 @@
   let rd = 0;
   let imm12 = 0b110000000000;
 }
+
+let Predicates = [HasStdExtZawrs] in {
+def WRS_NTO : RVInstI<0b000, OPC_SYSTEM, (outs), (ins), "wrs.nto", "">,
+              Sched<[]> {
+  let rs1 = 0;
+  let rd = 0;
+  let imm12 = 0b000000001101;
+}
+
+def WRS_STO : RVInstI<0b000, OPC_SYSTEM, (outs), (ins), "wrs.sto", "">,
+              Sched<[]> {
+  let rs1 = 0;
+  let rd = 0;
+  let imm12 = 0b000000011101;
+}
+} // Predicates = [HasStdExtZawrs]
+
 } // hasSideEffects = 1, mayLoad = 0, mayStore = 0
 
 def CSRRW : CSR_ir<0b001, "csrrw">;
Index: llvm/lib/Target/RISCV/RISCVSubtarget.h
===================================================================
--- llvm/lib/Target/RISCV/RISCVSubtarget.h
+++ llvm/lib/Target/RISCV/RISCVSubtarget.h
@@ -92,6 +92,7 @@
   bool HasStdExtZicboz = false;
   bool HasStdExtZicbop = false;
   bool HasStdExtZmmul = false;
+  bool HasStdExtZawrs = false;
   bool HasStdExtZtso = false;
   bool HasRV32 = false;
   bool HasRV64 = false;
@@ -192,6 +193,7 @@
   bool hasStdExtZicbom() const { return HasStdExtZicbom; }
   bool hasStdExtZicboz() const { return HasStdExtZicboz; }
   bool hasStdExtZicbop() const { return HasStdExtZicbop; }
+  bool hasStdExtZawrs() const { return HasStdExtZawrs; }
   bool hasStdExtZmmul() const { return HasStdExtZmmul; }
   bool hasStdExtZtso() const { return HasStdExtZtso; }
   bool is64Bit() const { return HasRV64; }
Index: llvm/test/CodeGen/RISCV/attributes.ll
===================================================================
--- llvm/test/CodeGen/RISCV/attributes.ll
+++ llvm/test/CodeGen/RISCV/attributes.ll
@@ -84,6 +84,7 @@
 ; RUN: llc -mtriple=riscv64 -mattr=+zicbom %s -o - | FileCheck --check-prefix=RV64ZICBOM %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zicboz %s -o - | FileCheck --check-prefix=RV64ZICBOZ %s
 ; RUN: llc -mtriple=riscv64 -mattr=+zicbop %s -o - | FileCheck --check-prefix=RV64ZICBOP %s
+; RUN: llc -mtriple=riscv64 -mattr=+experimental-zawrs %s -o - | FileCheck --check-prefix=RV64ZAWRS %s
 ; RUN: llc -mtriple=riscv64 -mattr=+experimental-ztso %s -o - | FileCheck --check-prefix=RV64ZTSO %s
 
 ; RV32M: .attribute 5, "rv32i2p0_m2p0"
@@ -170,6 +171,7 @@
 ; RV64COMBINEINTOZKS: .attribute 5, "rv64i2p0_zbkb1p0_zbkc1p0_zbkx1p0_zks1p0_zksed1p0_zksh1p0"
 ; RV64ZICBOM: .attribute 5, "rv64i2p0_zicbom1p0"
 ; RV64ZICBOZ: .attribute 5, "rv64i2p0_zicboz1p0"
+; RV64ZAWRS: .attribute 5, "rv64i2p0_zawrs1p0"
 ; RV64ZICBOP: .attribute 5, "rv64i2p0_zicbop1p0"
 ; RV64ZTSO: .attribute 5, "rv64i2p0_ztso0p1"
 
Index: llvm/test/MC/RISCV/Zawrs-valid.s
===================================================================
--- /dev/null
+++ llvm/test/MC/RISCV/Zawrs-valid.s
@@ -0,0 +1,18 @@
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+experimental-zawrs -riscv-no-aliases -show-encoding \
+# RUN:     | FileCheck -check-prefixes=CHECK-ASM,CHECK-ASM-AND-OBJ %s
+# RUN: llvm-mc %s -triple=riscv64 -mattr=+experimental-zawrs -riscv-no-aliases -show-encoding \
+# RUN:     | FileCheck -check-prefixes=CHECK-ASM,CHECK-ASM-AND-OBJ %s
+# RUN: llvm-mc -filetype=obj -triple=riscv32 -mattr=+experimental-zawrs < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-zawrs -M no-aliases -d -r - \
+# RUN:     | FileCheck --check-prefix=CHECK-ASM-AND-OBJ %s
+# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+experimental-zawrs < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-zawrs -M no-aliases -d -r - \
+# RUN:     | FileCheck --check-prefix=CHECK-ASM-AND-OBJ %s
+
+# CHECK-ASM-AND-OBJ: wrs.nto
+# CHECK-ASM: encoding: [0x73,0x00,0xd0,0x00]
+wrs.nto
+
+# CHECK-ASM-AND-OBJ: wrs.sto
+# CHECK-ASM: encoding: [0x73,0x00,0xd0,0x01]
+wrs.sto
Index: llvm/test/MC/RISCV/attribute-arch.s
===================================================================
--- llvm/test/MC/RISCV/attribute-arch.s
+++ llvm/test/MC/RISCV/attribute-arch.s
@@ -197,5 +197,8 @@
 .attribute arch, "rv32izca0p70"
 # CHECK: attribute      5, "rv32i2p0_zca0p70"
 
+.attribute arch, "rv32izawrs1p0"
+# CHECK: attribute      5, "rv32i2p0_zawrs1p0"
+
 .attribute arch, "rv32iztso0p1"
 # CHECK: attribute      5, "rv32i2p0_ztso0p1"