diff --git a/src/backend_x64/emit_x64_vector.cpp b/src/backend_x64/emit_x64_vector.cpp
index 77d4207a..fc4d1ccf 100644
--- a/src/backend_x64/emit_x64_vector.cpp
+++ b/src/backend_x64/emit_x64_vector.cpp
@@ -938,6 +938,61 @@ void EmitX64::EmitVectorPopulationCount(EmitContext& ctx, IR::Inst* inst) {
     });
 }
 
+void EmitX64::EmitVectorSignExtend8(EmitContext& ctx, IR::Inst* inst) {
+    auto args = ctx.reg_alloc.GetArgumentInfo(inst);
+    if (code.DoesCpuSupport(Xbyak::util::Cpu::tSSE41)) {
+        const Xbyak::Xmm a = ctx.reg_alloc.UseScratchXmm(args[0]);
+        code.pmovsxbw(a, a);
+        ctx.reg_alloc.DefineValue(inst, a);
+    } else {
+        const Xbyak::Xmm a = ctx.reg_alloc.UseXmm(args[0]);
+        const Xbyak::Xmm result = ctx.reg_alloc.ScratchXmm();
+        code.pxor(result, result);
+        code.punpcklbw(result, a);
+        code.psraw(result, 8);
+        ctx.reg_alloc.DefineValue(inst, result);
+    }
+}
+
+void EmitX64::EmitVectorSignExtend16(EmitContext& ctx, IR::Inst* inst) {
+    auto args = ctx.reg_alloc.GetArgumentInfo(inst);
+    if (code.DoesCpuSupport(Xbyak::util::Cpu::tSSE41)) {
+        const Xbyak::Xmm a = ctx.reg_alloc.UseScratchXmm(args[0]);
+        ctx.reg_alloc.DefineValue(inst, a);
+        code.pmovsxwd(a, a);
+    } else {
+        const Xbyak::Xmm a = ctx.reg_alloc.UseXmm(args[0]);
+        const Xbyak::Xmm result = ctx.reg_alloc.ScratchXmm();
+        code.pxor(result, result);
+        code.punpcklwd(result, a);
+        code.psrad(result, 16);
+        ctx.reg_alloc.DefineValue(inst, result);
+    }
+}
+
+void EmitX64::EmitVectorSignExtend32(EmitContext& ctx, IR::Inst* inst) {
+    if (code.DoesCpuSupport(Xbyak::util::Cpu::tSSE41)) {
+        auto args = ctx.reg_alloc.GetArgumentInfo(inst);
+        const Xbyak::Xmm a = ctx.reg_alloc.UseScratchXmm(args[0]);
+        code.pmovsxdq(a, a);
+        ctx.reg_alloc.DefineValue(inst, a);
+        return;
+    }
+
+    EmitOneArgumentFallback(code, ctx, inst, [](std::array<u64, 2>& result, const std::array<u32, 4>& a){
+        for (size_t i = 0; i < 2; ++i) {
+            result[i] = Common::SignExtend<32, u64>(a[i]);
+        }
+    });
+}
+
+void EmitX64::EmitVectorSignExtend64(EmitContext& ctx, IR::Inst* inst) {
+    EmitOneArgumentFallback(code, ctx, inst, [](std::array<u64, 2>& result, const std::array<u64, 2>& a){
+        result[1] = (a[0] >> 63) ? ~u64(0) : 0;
+        result[0] = a[0];
+    });
+}
+
 void EmitX64::EmitVectorSub8(EmitContext& ctx, IR::Inst* inst) {
     EmitVectorOperation(code, ctx, inst, &Xbyak::CodeGenerator::psubb);
 }
diff --git a/src/frontend/ir/ir_emitter.cpp b/src/frontend/ir/ir_emitter.cpp
index 1c79797c..960669b3 100644
--- a/src/frontend/ir/ir_emitter.cpp
+++ b/src/frontend/ir/ir_emitter.cpp
@@ -981,6 +981,21 @@ U128 IREmitter::VectorPopulationCount(const U128& a) {
     return Inst<U128>(Opcode::VectorPopulationCount, a);
 }
 
+U128 IREmitter::VectorSignExtend(size_t original_esize, const U128& a) {
+    switch (original_esize) {
+    case 8:
+        return Inst<U128>(Opcode::VectorSignExtend8, a);
+    case 16:
+        return Inst<U128>(Opcode::VectorSignExtend16, a);
+    case 32:
+        return Inst<U128>(Opcode::VectorSignExtend32, a);
+    case 64:
+        return Inst<U128>(Opcode::VectorSignExtend64, a);
+    }
+    UNREACHABLE();
+    return {};
+}
+
 U128 IREmitter::VectorSub(size_t esize, const U128& a, const U128& b) {
     switch (esize) {
     case 8:
diff --git a/src/frontend/ir/ir_emitter.h b/src/frontend/ir/ir_emitter.h
index c25d891f..29fcbdf7 100644
--- a/src/frontend/ir/ir_emitter.h
+++ b/src/frontend/ir/ir_emitter.h
@@ -224,6 +224,7 @@ public:
     U128 VectorPairedAdd(size_t esize, const U128& a, const U128& b);
     U128 VectorPairedAddLower(size_t esize, const U128& a, const U128& b);
     U128 VectorPopulationCount(const U128& a);
+    U128 VectorSignExtend(size_t original_esize, const U128& a);
     U128 VectorSub(size_t esize, const U128& a, const U128& b);
     U128 VectorZeroExtend(size_t original_esize, const U128& a);
     U128 VectorZeroUpper(const U128& a);
diff --git a/src/frontend/ir/opcodes.inc b/src/frontend/ir/opcodes.inc
index 85bd88b7..2e469304 100644
--- a/src/frontend/ir/opcodes.inc
+++ b/src/frontend/ir/opcodes.inc
@@ -249,6 +249,10 @@ OPCODE(VectorPairedAdd16,           T::U128,        T::U128,        T::U128
 OPCODE(VectorPairedAdd32,           T::U128,        T::U128,        T::U128                         )
 OPCODE(VectorPairedAdd64,           T::U128,        T::U128,        T::U128                         )
 OPCODE(VectorPopulationCount,       T::U128,        T::U128                                         )
+OPCODE(VectorSignExtend8,           T::U128,        T::U128                                         )
+OPCODE(VectorSignExtend16,          T::U128,        T::U128                                         )
+OPCODE(VectorSignExtend32,          T::U128,        T::U128                                         )
+OPCODE(VectorSignExtend64,          T::U128,        T::U128                                         )
 OPCODE(VectorSub8,                  T::U128,        T::U128,        T::U128                         )
 OPCODE(VectorSub16,                 T::U128,        T::U128,        T::U128                         )
 OPCODE(VectorSub32,                 T::U128,        T::U128,        T::U128                         )