diff --git a/cranelift/filetests/filetests/runtests/bitrev.clif b/cranelift/filetests/filetests/runtests/bitrev.clif
new file mode 100644
index 0000000000..2f3e7974e6
--- /dev/null
+++ b/cranelift/filetests/filetests/runtests/bitrev.clif
@@ -0,0 +1,40 @@
+test interpret
+test run
+target aarch64
+target x86_64
+
+function %bitrev_i8(i8) -> i8 {
+block0(v0: i8):
+    v1 = bitrev v0
+    return v1
+}
+; run: %bitrev_i8(1) == -128
+; run: %bitrev_i8(64) == 2
+; run: %bitrev_i8(-1) == -1
+
+function %bitrev_i16(i16) -> i16 {
+block0(v0: i16):
+    v1 = bitrev v0
+    return v1
+}
+; run: %bitrev_i16(1) == -32768
+; run: %bitrev_i16(16384) == 2
+; run: %bitrev_i16(-1) == -1
+
+function %bitrev_i32(i32) -> i32 {
+block0(v0: i32):
+    v1 = bitrev v0
+    return v1
+}
+; run: %bitrev_i32(1) == -2147483648
+; run: %bitrev_i32(1073741824) == 2
+; run: %bitrev_i32(-1) == -1
+
+function %bitrev_i64(i64) -> i64 {
+block0(v0: i64):
+    v1 = bitrev v0
+    return v1
+}
+; run: %bitrev_i64(1) == -9223372036854775808
+; run: %bitrev_i64(4611686018427387904) == 2
+; run: %bitrev_i64(-1) == -1
diff --git a/cranelift/filetests/filetests/runtests/cls-aarch64.clif b/cranelift/filetests/filetests/runtests/cls-aarch64.clif
new file mode 100644
index 0000000000..0c852028e8
--- /dev/null
+++ b/cranelift/filetests/filetests/runtests/cls-aarch64.clif
@@ -0,0 +1,24 @@
+test interpret
+test run
+target aarch64
+; not implemented on `x86_64`
+
+function %cls_i32(i32) -> i32 {
+block0(v0: i32):
+    v1 = cls v0
+    return v1
+}
+; run: %cls_i32(1) == 30
+; run: %cls_i32(0x40000000) == 0
+; run: %cls_i32(-1) == 31
+; run: %cls_i32(0) == 31
+
+function %cls_i64(i64) -> i64 {
+block0(v0: i64):
+    v1 = cls v0
+    return v1
+}
+; run: %cls_i64(1) == 62
+; run: %cls_i64(0x4000000000000000) == 0
+; run: %cls_i64(-1) == 63
+; run: %cls_i64(0) == 63
diff --git a/cranelift/filetests/filetests/runtests/cls-interpret.clif b/cranelift/filetests/filetests/runtests/cls-interpret.clif
new file mode 100644
index 0000000000..11c6826a9a
--- /dev/null
+++ b/cranelift/filetests/filetests/runtests/cls-interpret.clif
@@ -0,0 +1,23 @@
+test interpret
+; aarch64 yields cls_i8(1) == 30, which is incorrect
+
+function %cls_i8(i8) -> i8 {
+block0(v0: i8):
+    v1 = cls v0
+    return v1
+}
+; run: %cls_i8(1) == 6
+; run: %cls_i8(0x40) == 0
+; run: %cls_i8(-1) == 7
+; run: %cls_i8(0) == 7
+
+function %cls_i16(i16) -> i16 {
+block0(v0: i16):
+    v1 = cls v0
+    return v1
+}
+; run: %cls_i16(1) == 14
+; run: %cls_i16(0x4000) == 0
+; run: %cls_i16(-1) == 15
+; run: %cls_i16(0) == 15
+
diff --git a/cranelift/filetests/filetests/runtests/clz-interpret.clif b/cranelift/filetests/filetests/runtests/clz-interpret.clif
new file mode 100644
index 0000000000..bbacf0c28d
--- /dev/null
+++ b/cranelift/filetests/filetests/runtests/clz-interpret.clif
@@ -0,0 +1,19 @@
+test interpret
+
+function %clz_i8(i8) -> i8 {
+block0(v0: i8):
+    v1 = clz v0
+    return v1
+}
+; run: %clz_i8(1) == 7
+; run: %clz_i8(0x40) == 1
+; run: %clz_i8(-1) == 0
+
+function %clz_i16(i16) -> i16 {
+block0(v0: i16):
+    v1 = clz v0
+    return v1
+}
+; run: %clz_i16(1) == 15
+; run: %clz_i16(0x4000) == 1
+; run: %clz_i16(-1) == 0
\ No newline at end of file
diff --git a/cranelift/filetests/filetests/runtests/clz.clif b/cranelift/filetests/filetests/runtests/clz.clif
new file mode 100644
index 0000000000..b492bb0824
--- /dev/null
+++ b/cranelift/filetests/filetests/runtests/clz.clif
@@ -0,0 +1,22 @@
+test interpret
+test run
+target aarch64
+target x86_64
+
+function %clz_i32(i32) -> i32 {
+block0(v0: i32):
+    v1 = clz v0
+    return v1
+}
+; run: %clz_i32(1) == 31
+; run: %clz_i32(0x40000000) == 1
+; run: %clz_i32(-1) == 0
+
+function %clz_i64(i64) -> i64 {
+block0(v0: i64):
+    v1 = clz v0
+    return v1
+}
+; run: %clz_i64(1) == 63
+; run: %clz_i64(0x4000000000000000) == 1
+; run: %clz_i64(-1) == 0
diff --git a/cranelift/filetests/filetests/runtests/ctz-interpret.clif b/cranelift/filetests/filetests/runtests/ctz-interpret.clif
new file mode 100644
index 0000000000..21d074beb8
--- /dev/null
+++ b/cranelift/filetests/filetests/runtests/ctz-interpret.clif
@@ -0,0 +1,19 @@
+test interpret
+
+function %ctz_i8(i8) -> i8 {
+block0(v0: i8):
+    v1 = ctz v0
+    return v1
+}
+; run: %ctz_i8(1) == 0
+; run: %ctz_i8(0x40) == 6
+; run: %ctz_i8(-1) == 0
+
+function %ctz_i16(i16) -> i16 {
+block0(v0: i16):
+    v1 = ctz v0
+    return v1
+}
+; run: %ctz_i16(1) == 0
+; run: %ctz_i16(0x4000) == 14
+; run: %ctz_i16(-1) == 0
diff --git a/cranelift/filetests/filetests/runtests/ctz.clif b/cranelift/filetests/filetests/runtests/ctz.clif
new file mode 100644
index 0000000000..7d4ddd1d3a
--- /dev/null
+++ b/cranelift/filetests/filetests/runtests/ctz.clif
@@ -0,0 +1,22 @@
+test interpret
+test run
+target aarch64
+target x86_64
+
+function %ctz_i32(i32) -> i32 {
+block0(v0: i32):
+    v1 = ctz v0
+    return v1
+}
+; run: %ctz_i32(1) == 0
+; run: %ctz_i32(0x40000000) == 30
+; run: %ctz_i32(-1) == 0
+
+function %ctz_i64(i64) -> i64 {
+block0(v0: i64):
+    v1 = ctz v0
+    return v1
+}
+; run: %ctz_i64(1) == 0
+; run: %ctz_i64(0x4000000000000000) == 62
+; run: %ctz_i64(-1) == 0
diff --git a/cranelift/filetests/filetests/runtests/popcnt-aarch64.clif b/cranelift/filetests/filetests/runtests/popcnt-aarch64.clif
new file mode 100644
index 0000000000..99c2b2eca8
--- /dev/null
+++ b/cranelift/filetests/filetests/runtests/popcnt-aarch64.clif
@@ -0,0 +1,50 @@
+test interpret
+test run
+target aarch64
+
+function %popcnt_i8(i8) -> i8 {
+block0(v0: i8):
+    v1 = popcnt v0
+    return v1
+}
+; run: %popcnt_i8(1) == 1
+; run: %popcnt_i8(0x40) == 1
+; run: %popcnt_i8(-1) == 8
+; run: %popcnt_i8(0) == 0
+
+function %popcnt_i16(i16) -> i16 {
+block0(v0: i16):
+    v1 = popcnt v0
+    return v1
+}
+; run: %popcnt_i16(1) == 1
+; run: %popcnt_i16(0x4000) == 1
+; run: %popcnt_i16(-1) == 16
+; run: %popcnt_i16(0) == 0
+
+function %popcnt_i32(i32) -> i32 {
+block0(v0: i32):
+    v1 = popcnt v0
+    return v1
+}
+; run: %popcnt_i32(1) == 1
+; run: %popcnt_i32(0x40000000) == 1
+; run: %popcnt_i32(-1) == 32
+; run: %popcnt_i32(0) == 0
+
+function %popcnt_i64(i64) -> i64 {
+block0(v0: i64):
+    v1 = popcnt v0
+    return v1
+}
+; run: %popcnt_i64(1) == 1
+; run: %popcnt_i64(0x4000000000000000) == 1
+; run: %popcnt_i64(-1) == 64
+; run: %popcnt_i64(0) == 0
+
+function %popcnt_i8x16(i8x16) -> i8x16 {
+block0(v0: i8x16):
+    v1 = popcnt v0
+    return v1
+}
+; run: %popcnt_i8x16([1 1 1 1 0x40 0x40 0x40 0x40 0xff 0xff 0xff 0xff 0 0 0 0]) == [1 1 1 1 1 1 1 1 8 8 8 8 0 0 0 0]
diff --git a/cranelift/filetests/filetests/runtests/popcnt-interpret.clif b/cranelift/filetests/filetests/runtests/popcnt-interpret.clif
new file mode 100644
index 0000000000..ccca4f10d2
--- /dev/null
+++ b/cranelift/filetests/filetests/runtests/popcnt-interpret.clif
@@ -0,0 +1,24 @@
+test interpret
+; i16x8 vectors aren't currently supported by the `AArch64` backend.
+
+function %popcnt_i16x8(i16x8) -> i16x8 {
+block0(v0: i16x8):
+    v1 = popcnt v0
+    return v1
+}
+; run: %popcnt_i16x8([1 1 0x4000 0x4000 0xffff 0xffff 0 0]) == [1 1 1 1 16 16 0 0]
+
+function %popcnt_i32x4(i32x4) -> i32x4 {
+block0(v0: i32x4):
+    v1 = popcnt v0
+    return v1
+}
+; run: %popcnt_i32x4([1 0x40000000 0xFFFFFFFF 0]) == [1 1 32 0]
+
+function %popcnt_i64x2(i64x2) -> i64x2 {
+block0(v0: i64x2):
+    v1 = popcnt v0
+    return v1
+}
+; run: %popcnt_i64x2([1 0x4000000000000000]) == [1 1]
+; run: %popcnt_i64x2([0xffffffffffffffff 0]) == [64 0]
diff --git a/cranelift/interpreter/src/step.rs b/cranelift/interpreter/src/step.rs
index ce53528c20..802fea4645 100644
--- a/cranelift/interpreter/src/step.rs
+++ b/cranelift/interpreter/src/step.rs
@@ -668,11 +668,40 @@ where
         Opcode::IshlImm => binary(Value::shl, arg(0)?, imm_as_ctrl_ty()?)?,
         Opcode::UshrImm => binary(Value::ushr, arg(0)?, imm_as_ctrl_ty()?)?,
         Opcode::SshrImm => binary(Value::ishr, arg(0)?, imm_as_ctrl_ty()?)?,
-        Opcode::Bitrev => unimplemented!("Bitrev"),
-        Opcode::Clz => unimplemented!("Clz"),
-        Opcode::Cls => unimplemented!("Cls"),
-        Opcode::Ctz => unimplemented!("Ctz"),
-        Opcode::Popcnt => unimplemented!("Popcnt"),
+        Opcode::Bitrev => assign(Value::reverse_bits(arg(0)?)?),
+        // For `Clz`, `Cls`, `Ctz`, and `Popcnt`, the underlying Rust function
+        // always returns `u32` (and therefore a `Value` of type `U32`), so this
+        // is switched back to the correct type by recreating the `Value`.
+        Opcode::Clz => assign(Value::int(
+            Value::leading_zeros(arg(0)?)?.into_int()?,
+            ctrl_ty,
+        )?),
+        Opcode::Cls => {
+            let count = if Value::lt(&arg(0)?, &Value::int(0, ctrl_ty)?)? {
+                Value::int(Value::leading_ones(arg(0)?)?.into_int()?, ctrl_ty)?
+            } else {
+                Value::int(Value::leading_zeros(arg(0)?)?.into_int()?, ctrl_ty)?
+            };
+            assign(Value::sub(count, Value::int(1, ctrl_ty)?)?)
+        }
+        Opcode::Ctz => assign(Value::int(
+            Value::trailing_zeros(arg(0)?)?.into_int()?,
+            ctrl_ty,
+        )?),
+        Opcode::Popcnt => {
+            let count = if arg(0)?.ty().is_int() {
+                Value::int(Value::count_ones(arg(0)?)?.into_int()?, ctrl_ty)?
+            } else {
+                let lanes = extractlanes(&arg(0)?, ctrl_ty.lane_type())?;
+                let mut new_vec = SimdVec::new();
+                for i in lanes {
+                    let c: V = Value::count_ones(i)?;
+                    new_vec.push(c);
+                }
+                vectorizelanes(&new_vec, ctrl_ty)?
+            };
+            assign(count)
+        }
         Opcode::Fcmp => assign(Value::bool(
             fcmp(inst.fp_cond_code().unwrap(), &arg(0)?, &arg(1)?)?,
             ctrl_ty.as_bool(),
diff --git a/cranelift/interpreter/src/value.rs b/cranelift/interpreter/src/value.rs
index c76cacb0be..2f8fe47056 100644
--- a/cranelift/interpreter/src/value.rs
+++ b/cranelift/interpreter/src/value.rs
@@ -62,6 +62,13 @@ pub trait Value: Clone + From<DataValue> {
     fn or(self, other: Self) -> ValueResult<Self>;
     fn xor(self, other: Self) -> ValueResult<Self>;
     fn not(self) -> ValueResult<Self>;
+
+    // Bit counting.
+    fn count_ones(self) -> ValueResult<Self>;
+    fn leading_ones(self) -> ValueResult<Self>;
+    fn leading_zeros(self) -> ValueResult<Self>;
+    fn trailing_zeros(self) -> ValueResult<Self>;
+    fn reverse_bits(self) -> ValueResult<Self>;
 }
 
 #[derive(Error, Debug, PartialEq)]
@@ -132,6 +139,20 @@ pub enum ValueConversionKind {
 
 /// Helper for creating match expressions over [DataValue].
 macro_rules! unary_match {
+    ( $op:ident($arg1:expr); [ $( $data_value_ty:ident ),* ]; $return_value_ty:ident ) => {
+        match $arg1 {
+            $( DataValue::$data_value_ty(a) => {
+                Ok(DataValue::$return_value_ty(a.$op()))
+            } )*
+            _ => unimplemented!()
+        }
+    };
+    ( $op:ident($arg1:expr); [ $( $data_value_ty:ident ),* ] ) => {
+        match $arg1 {
+            $( DataValue::$data_value_ty(a) => { Ok(DataValue::$data_value_ty(a.$op())) } )*
+            _ => unimplemented!()
+        }
+    };
     ( $op:tt($arg1:expr); [ $( $data_value_ty:ident ),* ] ) => {
         match $arg1 {
             $( DataValue::$data_value_ty(a) => { Ok(DataValue::$data_value_ty($op a)) } )*
@@ -438,4 +459,24 @@ impl Value for DataValue {
     fn not(self) -> ValueResult<Self> {
         unary_match!(!(&self); [I8, I16, I32, I64])
     }
+
+    fn count_ones(self) -> ValueResult<Self> {
+        unary_match!(count_ones(&self); [I8, I16, I32, I64, I128, U8, U16, U32, U64, U128]; U32)
+    }
+
+    fn leading_ones(self) -> ValueResult<Self> {
+        unary_match!(leading_ones(&self); [I8, I16, I32, I64, I128, U8, U16, U32, U64, U128]; U32)
+    }
+
+    fn leading_zeros(self) -> ValueResult<Self> {
+        unary_match!(leading_zeros(&self); [I8, I16, I32, I64, I128, U8, U16, U32, U64, U128]; U32)
+    }
+
+    fn trailing_zeros(self) -> ValueResult<Self> {
+        unary_match!(trailing_zeros(&self); [I8, I16, I32, I64, I128, U8, U16, U32, U64, U128]; U32)
+    }
+
+    fn reverse_bits(self) -> ValueResult<Self> {
+        unary_match!(reverse_bits(&self); [I8, I16, I32, I64, I128, U8, U16, U32, U64, U128])
+    }
 }