Implement select and vselect instructions.

This gives us the opportunity to use the AsBool derived type variables and a
Select instruction format with a non-default typevar_operand setting.

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(

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
 #
 

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)