diff --git a/cl/_testrt/mask/in.go b/cl/_testrt/mask/in.go
index 18211c06..f5e266e5 100644
--- a/cl/_testrt/mask/in.go
+++ b/cl/_testrt/mask/in.go
@@ -2,7 +2,41 @@ package main
 
 func main() {
 	println(mask(1))
+	println(mask_shl(127, 5))
+	println(mask_shl8(127, 5))
+	println(mask_shl8u(127, 5))
+	println(mask_shl8(127, 16))
+	println(mask_shl8u(127, 16))
+	println(mask_shr(127, 5))
+	println(mask_shr8(127, 5))
+	println(mask_shr8u(127, 5))
+	println(mask_shr8(127, 16))
 }
+
 func mask(x int8) int32 {
 	return int32(x) << 31 >> 31
 }
+
+func mask_shl8(x int8, y int) int8 {
+	return x << y
+}
+
+func mask_shl8u(x uint8, y int) uint8 {
+	return x << y
+}
+
+func mask_shl(x int, y int) int {
+	return x << y
+}
+
+func mask_shr8(x int8, y int) int8 {
+	return x >> y
+}
+
+func mask_shr8u(x uint8, y int) uint8 {
+	return x >> y
+}
+
+func mask_shr(x int, y int) int {
+	return x >> y
+}
diff --git a/cl/_testrt/mask/out.ll b/cl/_testrt/mask/out.ll
index bea4f657..c64b738f 100644
--- a/cl/_testrt/mask/out.ll
+++ b/cl/_testrt/mask/out.ll
@@ -7,6 +7,21 @@ source_filename = "main"
 @__llgo_argc = global ptr null
 @__llgo_argv = global ptr null
 @0 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@1 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@2 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@3 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@4 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@5 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@6 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@7 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@8 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@9 = private unnamed_addr constant [2 x i8] c"\0A\00", align 1
+@10 = private unnamed_addr constant [22 x i8] c"negative shift amount\00", align 1
+@11 = private unnamed_addr constant [22 x i8] c"negative shift amount\00", align 1
+@12 = private unnamed_addr constant [22 x i8] c"negative shift amount\00", align 1
+@13 = private unnamed_addr constant [22 x i8] c"negative shift amount\00", align 1
+@14 = private unnamed_addr constant [22 x i8] c"negative shift amount\00", align 1
+@15 = private unnamed_addr constant [22 x i8] c"negative shift amount\00", align 1
 
 define void @main.init() {
 _llgo_0:
@@ -32,6 +47,49 @@ _llgo_0:
   call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %3)
   %4 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @0, i64 1)
   call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %4)
+  %5 = call i64 @main.mask_shl(i64 127, i64 5)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %5)
+  %6 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @1, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %6)
+  %7 = call i8 @main.mask_shl8(i8 127, i64 5)
+  %8 = sext i8 %7 to i64
+  call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %8)
+  %9 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @2, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %9)
+  %10 = call i8 @main.mask_shl8u(i8 127, i64 5)
+  %11 = sext i8 %10 to i64
+  call void @"github.com/goplus/llgo/internal/runtime.PrintUint"(i64 %11)
+  %12 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @3, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %12)
+  %13 = call i8 @main.mask_shl8(i8 127, i64 16)
+  %14 = sext i8 %13 to i64
+  call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %14)
+  %15 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @4, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %15)
+  %16 = call i8 @main.mask_shl8u(i8 127, i64 16)
+  %17 = sext i8 %16 to i64
+  call void @"github.com/goplus/llgo/internal/runtime.PrintUint"(i64 %17)
+  %18 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @5, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %18)
+  %19 = call i64 @main.mask_shr(i64 127, i64 5)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %19)
+  %20 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @6, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %20)
+  %21 = call i8 @main.mask_shr8(i8 127, i64 5)
+  %22 = sext i8 %21 to i64
+  call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %22)
+  %23 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @7, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %23)
+  %24 = call i8 @main.mask_shr8u(i8 127, i64 5)
+  %25 = sext i8 %24 to i64
+  call void @"github.com/goplus/llgo/internal/runtime.PrintUint"(i64 %25)
+  %26 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @8, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %26)
+  %27 = call i8 @main.mask_shr8(i8 127, i64 16)
+  %28 = sext i8 %27 to i64
+  call void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64 %28)
+  %29 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @9, i64 1)
+  call void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String" %29)
   ret void
 }
 
@@ -39,8 +97,79 @@ define i32 @main.mask(i8 %0) {
 _llgo_0:
   %1 = sext i8 %0 to i32
   %2 = shl i32 %1, 31
-  %3 = ashr i32 %2, 31
-  ret i32 %3
+  %3 = select i1 false, i32 0, i32 %2
+  %4 = ashr i32 %3, 31
+  ret i32 %4
+}
+
+define i64 @main.mask_shl(i64 %0, i64 %1) {
+_llgo_0:
+  %2 = icmp slt i64 %1, 0
+  %3 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @10, i64 21)
+  call void @"github.com/goplus/llgo/internal/runtime.CheckRuntimeError"(i1 %2, %"github.com/goplus/llgo/internal/runtime.String" %3)
+  %4 = icmp uge i64 %1, 64
+  %5 = shl i64 %0, %1
+  %6 = select i1 %4, i64 0, i64 %5
+  ret i64 %6
+}
+
+define i8 @main.mask_shl8(i8 %0, i64 %1) {
+_llgo_0:
+  %2 = icmp slt i64 %1, 0
+  %3 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @11, i64 21)
+  call void @"github.com/goplus/llgo/internal/runtime.CheckRuntimeError"(i1 %2, %"github.com/goplus/llgo/internal/runtime.String" %3)
+  %4 = trunc i64 %1 to i8
+  %5 = icmp uge i8 %4, 8
+  %6 = shl i8 %0, %4
+  %7 = select i1 %5, i8 0, i8 %6
+  ret i8 %7
+}
+
+define i8 @main.mask_shl8u(i8 %0, i64 %1) {
+_llgo_0:
+  %2 = icmp slt i64 %1, 0
+  %3 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @12, i64 21)
+  call void @"github.com/goplus/llgo/internal/runtime.CheckRuntimeError"(i1 %2, %"github.com/goplus/llgo/internal/runtime.String" %3)
+  %4 = trunc i64 %1 to i8
+  %5 = icmp uge i8 %4, 8
+  %6 = shl i8 %0, %4
+  %7 = select i1 %5, i8 0, i8 %6
+  ret i8 %7
+}
+
+define i64 @main.mask_shr(i64 %0, i64 %1) {
+_llgo_0:
+  %2 = icmp slt i64 %1, 0
+  %3 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @13, i64 21)
+  call void @"github.com/goplus/llgo/internal/runtime.CheckRuntimeError"(i1 %2, %"github.com/goplus/llgo/internal/runtime.String" %3)
+  %4 = icmp uge i64 %1, 64
+  %5 = select i1 %4, i64 63, i64 %1
+  %6 = ashr i64 %0, %5
+  ret i64 %6
+}
+
+define i8 @main.mask_shr8(i8 %0, i64 %1) {
+_llgo_0:
+  %2 = icmp slt i64 %1, 0
+  %3 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @14, i64 21)
+  call void @"github.com/goplus/llgo/internal/runtime.CheckRuntimeError"(i1 %2, %"github.com/goplus/llgo/internal/runtime.String" %3)
+  %4 = trunc i64 %1 to i8
+  %5 = icmp uge i8 %4, 8
+  %6 = select i1 %5, i8 7, i8 %4
+  %7 = ashr i8 %0, %6
+  ret i8 %7
+}
+
+define i8 @main.mask_shr8u(i8 %0, i64 %1) {
+_llgo_0:
+  %2 = icmp slt i64 %1, 0
+  %3 = call %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr @15, i64 21)
+  call void @"github.com/goplus/llgo/internal/runtime.CheckRuntimeError"(i1 %2, %"github.com/goplus/llgo/internal/runtime.String" %3)
+  %4 = trunc i64 %1 to i8
+  %5 = icmp uge i8 %4, 8
+  %6 = lshr i8 %0, %4
+  %7 = select i1 %5, i8 0, i8 %6
+  ret i8 %7
 }
 
 declare void @"github.com/goplus/llgo/internal/runtime.init"()
@@ -50,3 +179,7 @@ declare void @"github.com/goplus/llgo/internal/runtime.PrintInt"(i64)
 declare void @"github.com/goplus/llgo/internal/runtime.PrintString"(%"github.com/goplus/llgo/internal/runtime.String")
 
 declare %"github.com/goplus/llgo/internal/runtime.String" @"github.com/goplus/llgo/internal/runtime.NewString"(ptr, i64)
+
+declare void @"github.com/goplus/llgo/internal/runtime.PrintUint"(i64)
+
+declare void @"github.com/goplus/llgo/internal/runtime.CheckRuntimeError"(i1, %"github.com/goplus/llgo/internal/runtime.String")
diff --git a/internal/runtime/error.go b/internal/runtime/error.go
new file mode 100644
index 00000000..a33d69db
--- /dev/null
+++ b/internal/runtime/error.go
@@ -0,0 +1,15 @@
+package runtime
+
+type errorString string
+
+func (e errorString) RuntimeError() {}
+
+func (e errorString) Error() string {
+	return "runtime error: " + string(e)
+}
+
+func CheckRuntimeError(b bool, s string) {
+	if b {
+		panic(errorString(s).Error())
+	}
+}
diff --git a/internal/runtime/llgo_autogen.lla b/internal/runtime/llgo_autogen.lla
index 908e7b58..652fbb7f 100644
Binary files a/internal/runtime/llgo_autogen.lla and b/internal/runtime/llgo_autogen.lla differ
diff --git a/ssa/expr.go b/ssa/expr.go
index 7dfa45a0..1ebf1973 100644
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -320,20 +320,36 @@ func (b Builder) BinOp(op token.Token, x, y Expr) Expr {
 			}
 		}
 	case isLogicOp(op): // op: & | ^ << >> &^
-		if op == token.AND_NOT {
+		switch op {
+		case token.AND_NOT:
 			return Expr{b.impl.CreateAnd(x.impl, b.impl.CreateNot(y.impl, ""), ""), x.Type}
-		}
-		kind := x.kind
-		llop := logicOpToLLVM[op-logicOpBase]
-		if op == token.SHR && kind == vkUnsigned {
-			llop = llvm.LShr // Logical Shift Right
-		}
-		if op == token.SHL || op == token.SHR {
-			if b.Prog.SizeOf(x.Type) != b.Prog.SizeOf(y.Type) {
+		case token.SHL, token.SHR:
+			if y.kind == vkSigned {
+				check := Expr{b.impl.CreateICmp(llvm.IntSLT, y.impl, llvm.ConstInt(y.ll, 0, false), ""), b.Prog.Bool()}
+				b.InlineCall(b.Func.Pkg.rtFunc("CheckRuntimeError"), check, b.Str("negative shift amount"))
+			}
+			xsize, ysize := b.Prog.SizeOf(x.Type), b.Prog.SizeOf(y.Type)
+			if xsize != ysize {
 				y = b.Convert(x.Type, y)
 			}
+			overflows := b.impl.CreateICmp(llvm.IntUGE, y.impl, llvm.ConstInt(y.ll, xsize*8, false), "")
+			xzero := llvm.ConstInt(x.ll, 0, false)
+			if op == token.SHL {
+				rhs := b.impl.CreateShl(x.impl, y.impl, "")
+				return Expr{b.impl.CreateSelect(overflows, xzero, rhs, ""), x.Type}
+			} else {
+				if x.kind == vkSigned {
+					rhs := b.impl.CreateSelect(overflows, llvm.ConstInt(y.ll, 8*xsize-1, false), y.impl, "")
+					return Expr{b.impl.CreateAShr(x.impl, rhs, ""), x.Type}
+				} else {
+					rsh := b.impl.CreateLShr(x.impl, y.impl, "")
+					return Expr{b.impl.CreateSelect(overflows, xzero, rsh, ""), x.Type}
+				}
+			}
+		default:
+			llop := logicOpToLLVM[op-logicOpBase]
+			return Expr{llvm.CreateBinOp(b.impl, llop, x.impl, y.impl), x.Type}
 		}
-		return Expr{llvm.CreateBinOp(b.impl, llop, x.impl, y.impl), x.Type}
 	case isPredOp(op): // op: == != < <= < >=
 		tret := b.Prog.Bool()
 		kind := x.kind
diff --git a/ssa/ssa_test.go b/ssa/ssa_test.go
index 13a98552..daac56f2 100644
--- a/ssa/ssa_test.go
+++ b/ssa/ssa_test.go
@@ -446,7 +446,7 @@ func TestUnOp(t *testing.T) {
 	b := fn.MakeBody(1)
 	ptr := fn.Param(0)
 	val := b.UnOp(token.MUL, ptr)
-	val2 := b.BinOp(token.SHR, val, prog.Val(1))
+	val2 := b.BinOp(token.XOR, val, prog.Val(1))
 	b.Store(ptr, val2)
 	b.Return(val2)
 	assertPkg(t, pkg, `; ModuleID = 'foo/bar'
@@ -455,7 +455,7 @@ source_filename = "foo/bar"
 define i64 @fn(ptr %0) {
 _llgo_0:
   %1 = load i64, ptr %0, align 4
-  %2 = ashr i64 %1, 1
+  %2 = xor i64 %1, 1
   store i64 %2, ptr %0, align 4
   ret i64 %2
 }