diff --git a/cranelift/docs/cton_domain.py b/cranelift/docs/cton_domain.py
index e1dc08a67b..823ed9c8a5 100644
--- a/cranelift/docs/cton_domain.py
+++ b/cranelift/docs/cton_domain.py
@@ -13,6 +13,7 @@
 import re
 
 from docutils import nodes
+from docutils.parsers.rst import directives
 
 from sphinx import addnodes
 from sphinx.directives import ObjectDescription
@@ -22,6 +23,8 @@ from sphinx.roles import XRefRole
 from sphinx.util.docfields import Field, GroupedField, TypedField
 from sphinx.util.nodes import make_refnode
 
+import sphinx.ext.autodoc
+
 class CtonObject(ObjectDescription):
     """
     Any kind of Cretonne IL object.
@@ -29,6 +32,11 @@ class CtonObject(ObjectDescription):
     This is a shared base class for the different kinds of indexable objects
     in the Cretonne IL reference.
     """
+    option_spec = {
+        'noindex': directives.flag,
+        'module': directives.unchanged,
+        'annotation': directives.unchanged,
+    }
 
     def add_target_and_index(self, name, sig, signode):
         """
@@ -209,7 +217,33 @@ class CretonneDomain(Domain):
                  make_refnode(builder, fromdocname, obj[0],
                               obj[1] + '-' + target, contnode, target))]
 
+
+class TypeDocumenter(sphinx.ext.autodoc.Documenter):
+    # Invoke with .. autoctontype::
+    objtype = 'ctontype'
+    # Convert into cton:type directives
+    domain = 'cton'
+    directivetype = 'type'
+
+    @classmethod
+    def can_document_member(cls, member, membername, isattr, parent):
+        return False
+
+    def resolve_name(self, modname, parents, path, base):
+        return 'cretonne.types', [ base ]
+
+    def add_content(self, more_content, no_docstring=False):
+        super(TypeDocumenter, self).add_content(more_content, no_docstring)
+        sourcename = self.get_sourcename()
+        membytes = self.object.membytes
+        if membytes:
+            self.add_line(u':bytes: {}'.format(membytes), sourcename)
+        else:
+            self.add_line(u':bytes: Can\'t be stored in memory', sourcename)
+
+
 def setup(app):
     app.add_domain(CretonneDomain)
+    app.add_autodocumenter(TypeDocumenter)
 
     return { 'version' : '0.1' }
diff --git a/cranelift/docs/langref.rst b/cranelift/docs/langref.rst
index 0f12a7489e..ad2ccb4299 100644
--- a/cranelift/docs/langref.rst
+++ b/cranelift/docs/langref.rst
@@ -87,10 +87,7 @@ All SSA values have a type which determines the size and shape (for SIMD
 vectors) of the value. Many instructions are polymorphic -- they can operate on
 different types.
 
-.. type:: bool
-
-    A boolean value that is either true or false. Booleans can't be stored in
-    memory.
+.. autoctontype:: bool
 
 Integer types
 -------------
@@ -99,21 +96,10 @@ Integer values have a fixed size and can be interpreted as either signed or
 unsigned. Some instructions will interpret an operand as a signed or unsigned
 number, others don't care.
 
-.. type:: i8
-
-    A 8-bit integer value taking up 1 byte in memory.
-
-.. type:: i16
-
-    A 16-bit integer value taking up 2 bytes in memory.
-
-.. type:: i32
-
-    A 32-bit integer value taking up 4 bytes in memory.
-
-.. type:: i64
-
-    A 64-bit integer value taking up 8 bytes in memory.
+.. autoctontype:: i8
+.. autoctontype:: i16
+.. autoctontype:: i32
+.. autoctontype:: i64
 
 Floating point types
 --------------------
@@ -122,17 +108,8 @@ The floating point types have the IEEE semantics that are supported by most
 hardware. There is no support for higher-precision types like quads or
 double-double formats.
 
-.. type:: f32
-
-    A 32-bit floating point type represented in the IEEE 754 *single precision*
-    format. This corresponds to the :c:type:`float` type in most C
-    implementations.
-
-.. type:: f64
-
-    A 64-bit floating point type represented in the IEEE 754 *double precision*
-    format. This corresponds to the :c:type:`double` type in most C
-    implementations.
+.. autoctontype:: f32
+.. autoctontype:: f64
 
 SIMD vector types
 -----------------
@@ -201,7 +178,7 @@ in this reference.
 
 .. type:: fB
 
-    Either of the floating point scalar types: :type:`f32` or :type:`f64.
+    Either of the floating point scalar types: :type:`f32` or :type:`f64`.
 
 .. type:: Float
 
diff --git a/meta/cretonne/__init__.py b/meta/cretonne/__init__.py
index 9133f8e062..216607c9dc 100644
--- a/meta/cretonne/__init__.py
+++ b/meta/cretonne/__init__.py
@@ -12,6 +12,11 @@ instructions.
 class Type(object):
     """A concrete value type."""
 
+    def __init__(self, name, membytes, doc):
+        self.name = name
+        self.membytes = membytes
+        self.__doc__ = doc
+
     def __str__(self):
         return self.name
 
@@ -19,12 +24,12 @@ class ScalarType(Type):
     """
     A concrete scalar (not vector) type.
 
-    Also tracks a unique set of :class:`VectorType` instances with this type as
-    the lane type.
+    Also tracks a unique set of :py:class:`VectorType` instances with this type
+    as the lane type.
     """
 
-    def __init__(self, name):
-        self.name = name
+    def __init__(self, name, membytes, doc):
+        super(ScalarType, self).__init__(name, membytes, doc)
         self._vectors = dict()
 
     def __repr__(self):
@@ -53,9 +58,14 @@ class VectorType(Type):
 
     def __init__(self, base, lanes):
         assert isinstance(base, ScalarType), 'SIMD lanes must be scalar types'
+        super(VectorType, self).__init__(
+                name='{}x{}'.format(base.name, lanes),
+                membytes=lanes*base.membytes,
+                doc="""
+                A SIMD vector with {} lanes containing a {} each.
+                """.format(lanes, base.name))
         self.base = base
         self.lanes = lanes
-        self.name = '{}x{}'.format(base.name, lanes)
 
     def __repr__(self):
         return 'VectorType(base={}, lanes={})'.format(self.base.name, self.lanes)
@@ -65,7 +75,10 @@ class IntType(ScalarType):
 
     def __init__(self, bits):
         assert bits > 0, 'IntType must have positive number of bits'
-        super(IntType, self).__init__('i{:d}'.format(bits))
+        super(IntType, self).__init__(
+                name='i{:d}'.format(bits),
+                membytes=bits/8,
+                doc="An integer type with {} bits.".format(bits))
         self.bits = bits
 
     def __repr__(self):
@@ -74,9 +87,9 @@ class IntType(ScalarType):
 class FloatType(ScalarType):
     """A concrete scalar floating point type."""
 
-    def __init__(self, bits):
+    def __init__(self, bits, doc):
         assert bits > 0, 'FloatType must have positive number of bits'
-        super(FloatType, self).__init__('f{:d}'.format(bits))
+        super(FloatType, self).__init__( name='f{:d}'.format(bits), membytes=bits/8, doc=doc)
         self.bits = bits
 
     def __repr__(self):
diff --git a/meta/cretonne/types.py b/meta/cretonne/types.py
index 382fe0def2..27a74aec67 100644
--- a/meta/cretonne/types.py
+++ b/meta/cretonne/types.py
@@ -2,19 +2,32 @@
 
 from . import ScalarType, IntType, FloatType
 
-#: A boolean value.
-bool = ScalarType('bool')
+bool = ScalarType('bool', 0,
+        """
+        A boolean value that is either true or false.
+        """)
 
-i8  = IntType(8)  #: 8-bit int.
-i16 = IntType(16) #: 16-bit int.
-i32 = IntType(32) #: 32-bit int.
-i64 = IntType(64) #: 64-bit int.
+i8  = IntType(8)
+i16 = IntType(16)
+i32 = IntType(32)
+i64 = IntType(64)
 
-f32 = FloatType(32) #: IEEE 32-bit float.
-f64 = FloatType(64) #: IEEE 64-bit float
+f32 = FloatType(32,
+        """
+        A 32-bit floating point type represented in the IEEE 754-2008 *binary32*
+        interchange format. This corresponds to the :c:type:`float` type in most
+        C implementations.
+        """)
 
-i8x16 = i8.by(16) #: Vector of 16 i8 lanes.
+f64 = FloatType(64,
+        """
+        A 64-bit floating point type represented in the IEEE 754-2008 *binary64*
+        interchange format. This corresponds to the :c:type:`double` type in
+        most C implementations.
+        """)
 
-f32x4 = f32.by(4) #: Vector of 4 f32 lanes.
-f64x2 = f64.by(2) #: Vector of 2 f64 lanes.
+i8x16 = i8.by(16)
+
+f32x4 = f32.by(4)
+f64x2 = f64.by(2)