diff --git a/docs/langref.rst b/docs/langref.rst
index ca58a9b273..05ebfa9e05 100644
--- a/docs/langref.rst
+++ b/docs/langref.rst
@@ -656,35 +656,12 @@ load a constant into an SSA value.
 .. autoinst:: f32const
 .. autoinst:: f64const
 .. autoinst:: vconst
-
-.. inst:: a = select c, x, y
-
-    Conditional select.
-
-    :arg b1 c: Controlling flag.
-    :arg T x: Value to return when ``c`` is true.
-    :arg T y: Value to return when ``c`` is false. Must be same type as ``x``.
-    :result T a: Same type as ``x`` and ``y``.
-
-    This instruction selects whole values. Use :inst:`vselect` for lane-wise
-    selection.
+.. autoinst:: select
 
 Vector operations
 -----------------
 
-.. inst:: a  = vselect c, x, y
-
-    Vector lane select.
-
-    Select lanes from ``x`` or ``y`` controlled by the lanes of the boolean
-    vector ``c``.
-
-    :arg b1xN c: Controlling flag vector.
-    :arg TxN x: Vector with lanes selected by the true lanes of ``c``.
-              Must be a vector type with the same number of lanes as ``c``.
-    :arg TxN y: Vector with lanes selected by the false lanes of ``c``.
-              Must be same type as ``x``.
-    :result TxN a: Same type as ``x`` and ``y``.
+.. autoinst:: vselect
 
 .. inst:: a = vbuild x, y, z, ...
 
diff --git a/meta/cretonne/__init__.py b/meta/cretonne/__init__.py
index 2c737c2e7e..c0eec9e970 100644
--- a/meta/cretonne/__init__.py
+++ b/meta/cretonne/__init__.py
@@ -283,6 +283,7 @@ class TypeVar(object):
         if self.is_derived:
             assert derived_func
             self.derived_func = derived_func
+            self.name = '{}({})'.format(derived_func, base.name)
         else:
             self.type_set = TypeSet(
                     allow_scalars=scalars,
@@ -303,18 +304,14 @@ class TypeVar(object):
         When this type variable assumes a scalar type, the derived type will be
         the same scalar type.
         """
-        return TypeVar(
-                "Lane type of " + self.name, '',
-                base=self, derived_func='Lane')
+        return TypeVar(None, None, base=self, derived_func='Lane')
 
     def as_bool(self):
         """
         Return a derived type variable that has the same vector geometry as
         this type variable, but with boolean lanes. Scalar types map to `b1`.
         """
-        return TypeVar(
-                self.name + " as boolean", '',
-                base=self, derived_func='AsBool')
+        return TypeVar(None, None, base=self, derived_func='AsBool')
 
     def operand_kind(self):
         # When a `TypeVar` object is used to describe the type of an `Operand`
@@ -607,8 +604,8 @@ class Instruction(object):
             # No other derived typevars allowed.
             if typ is not tv:
                 raise RuntimeError(
-                        "type variable {} must not be derived from {}"
-                        .format(typ.name, tv.name))
+                        "{}: type variable {} must be derived from {}"
+                        .format(self.ins[opidx], typ.name, ctrl_typevar))
             # Other free type variables can only be used once each.
             if tv in other_tvs:
                 raise RuntimeError(
diff --git a/meta/cretonne/base.py b/meta/cretonne/base.py
index 9e13377ed6..c28c3724a2 100644
--- a/meta/cretonne/base.py
+++ b/meta/cretonne/base.py
@@ -19,6 +19,9 @@ Testable = TypeVar(
 TxN = TypeVar(
         '%Tx%N', 'A SIMD vector type',
         ints=True, floats=True, bools=True, scalars=False, simd=True)
+Any = TypeVar(
+        'Any', 'Any integer, float, or boolean scalar or vector type',
+        ints=True, floats=True, bools=True, scalars=True, simd=True)
 
 #
 # Control flow
@@ -140,6 +143,41 @@ vconst = Instruction(
         ins=N, outs=a)
 
 #
+# Generics.
+#
+
+c = Operand('c', Testable, doc='Controlling value to test')
+x = Operand('x', Any, doc='Value to use when `c` is true')
+y = Operand('y', Any, doc='Value to use when `c` is false')
+a = Operand('a', Any)
+
+select = Instruction(
+        'select', r"""
+        Conditional select.
+
+        This instruction selects whole values. Use :inst:`vselect` for
+        lane-wise selection.
+        """,
+        ins=(c, x, y), outs=a)
+
+#
+# Vector operations
+#
+
+c = Operand('c', TxN.as_bool(), doc='Controlling vector')
+x = Operand('x', TxN, doc='Value to use where `c` is true')
+y = Operand('y', TxN, doc='Value to use where `c` is false')
+a = Operand('a', TxN)
+
+vselect = Instruction(
+        'vselect', r"""
+        Vector lane select.
+
+        Select lanes from ``x`` or ``y`` controlled by the lanes of the boolean
+        vector ``c``.
+        """,
+        ins=(c, x, y), outs=a)
+#
 # Integer arithmetic
 #
 
diff --git a/meta/cretonne/formats.py b/meta/cretonne/formats.py
index 261b400321..4843befea9 100644
--- a/meta/cretonne/formats.py
+++ b/meta/cretonne/formats.py
@@ -26,6 +26,10 @@ BinaryImmRev = InstructionFormat(imm64, value)
 # Generate result + overflow flag.
 BinaryOverflow = InstructionFormat(value, value, multiple_results=True)
 
+# The select instructions are controlled by the second value operand.
+# The first value operand is the controlling flag whisch has a derived type.
+Select = InstructionFormat(value, value, value, typevar_operand=1)
+
 Jump = InstructionFormat(ebb, variable_args, boxed_storage=True)
 Branch = InstructionFormat(value, ebb, variable_args, boxed_storage=True)
 BranchTable = InstructionFormat(value, jump_table)
diff --git a/src/libcretonne/instructions.rs b/src/libcretonne/instructions.rs
index c6b353ae9c..d1861fb669 100644
--- a/src/libcretonne/instructions.rs
+++ b/src/libcretonne/instructions.rs
@@ -158,6 +158,11 @@ pub enum InstructionData {
         second_result: Value,
         args: [Value; 2],
     },
+    Select {
+        opcode: Opcode,
+        ty: Type,
+        args: [Value; 3],
+    },
     Jump {
         opcode: Opcode,
         ty: Type,
@@ -295,13 +300,13 @@ impl InstructionData {
 ///
 /// Bits 4-7:
 ///     Permitted set of types for the controlling type variable as an index into `TYPE_SETS`.
-/// 
+///
 /// Bits 8-15:
 ///     Offset into `OPERAND_CONSTRAINT` table of the descriptors for this opcode. The first
 ///     `fixed_results()` entries describe the result constraints, then follows constraints for the
 ///     fixed `Value` input operands. The number of `Value` inputs isdetermined by the instruction
 ///     format.
-///   
+///
 #[derive(Clone, Copy)]
 pub struct OpcodeConstraints(u16);
 
diff --git a/src/libcretonne/write.rs b/src/libcretonne/write.rs
index d3a676293d..e6eb3a477f 100644
--- a/src/libcretonne/write.rs
+++ b/src/libcretonne/write.rs
@@ -156,6 +156,9 @@ pub fn write_instruction(w: &mut Write, func: &Function, inst: Inst) -> Result {
         BinaryImm { opcode, lhs, rhs, .. } => writeln!(w, "{} {}, {}", opcode, lhs, rhs),
         BinaryImmRev { opcode, lhs, rhs, .. } => writeln!(w, "{} {}, {}", opcode, lhs, rhs),
         BinaryOverflow { opcode, args, .. } => writeln!(w, "{} {}, {}", opcode, args[0], args[1]),
+        Select { opcode, args, .. } => {
+            writeln!(w, "{} {}, {}, {}", opcode, args[0], args[1], args[2])
+        }
         Jump { opcode, ref data, .. } => writeln!(w, "{} {}", opcode, data),
         Branch { opcode, ref data, .. } => writeln!(w, "{} {}", opcode, data),
         BranchTable { opcode, arg, table, .. } => writeln!(w, "{} {}, {}", opcode, arg, table),
diff --git a/src/libreader/parser.rs b/src/libreader/parser.rs
index 2247259530..6aab089330 100644
--- a/src/libreader/parser.rs
+++ b/src/libreader/parser.rs
@@ -668,6 +668,7 @@ impl<'a> Parser<'a> {
                     args: [lhs, rhs],
                 }
             }
+            InstructionFormat::Select |
             InstructionFormat::Jump |
             InstructionFormat::Branch |
             InstructionFormat::BranchTable |