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Explain how to declare and update boolean bitfields.

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SegPrefs are not necessarily to do with segments.

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Gareth Rees 2014-04-17 23:41:09 +01:00
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45
mps/design/type.txt
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@ -151,6 +151,14 @@ compared ``w3i3mv\hi\amcss.exe`` running with and without the macro
for ``BoolCheck`` on the PC Aaron. "With" ran in 97.7% of the time
(averaged over 3 runs).
_`.bool.bitfield`: When a Boolean needs to be stored in a bitfield,
the type of the bitfield must be ``unsigned:1``, not ``Bool:1``.
(That's because the two values of the type ``Bool:1`` are ``0`` and
``-1``, which means that assigning ``TRUE`` would require a sign
conversion.) To avoid warnings about loss of data from GCC with the
``-Wconversion`` option, ``misc.h`` provides the ``BOOL`` macro for
coercing a value to an unsigned single-bit field.
``typedef unsigned BufferMode``
@ -235,7 +243,8 @@ objects.
``typedef Size Epoch``
_`.epoch`: An ``Epoch`` is a count of the number of flips that have
occurred. It is used in the implementation of location dependencies.
occurred, in which objects may have moved. It is used in the
implementation of location dependencies.
``Epoch`` is converted to ``mps_word_t`` in the MPS C Interface, as a
field of ``mps_ld_s``.
@ -351,7 +360,7 @@ references must be scanned in order to respect the properties of
references of the ranks. Therefore they are declared explicitly with
their integer values.
.. note:: Could ``Rank`` be a ``short``?
.. note:: Could ``Rank`` be an ``unsigned short`` or ``unsigned char``?
.. note::
@ -459,30 +468,35 @@ create a valid registered constant root that contains any references.
become invalid; but you can't add them afterwards because the root is
supposed to be constant.)
_`.rootmode.conv.c`: ``RootMode`` is converted to ``mps_rm_t`` in the MPS C
Interface.
_`.rootmode.conv.c`: ``RootMode`` is converted to ``mps_rm_t`` in the
MPS C Interface.
``typedef int RootVar``
_`.rootvar`: The type ``RootVar`` is the type of the
discriminator for the union within ``RootStruct``.
_`.rootvar`: The type ``RootVar`` is the type of the discriminator for
the union within ``RootStruct``.
``typedef int SegPrefKind``
_`.segprefkind`: The type ``SegPrefKind`` expresses a preference about
where the arena should place a segment. It takes one of the following
_`.segprefkind`: The type ``SegPrefKind`` expresses a preference for
addresses within an address space. It takes one of the following
values:
================== ====================================================
Kind Description
================== ====================================================
``SegPrefHigh`` Place the segment high in the address space.
``SegPrefLow`` Place the segment low in the address space.
``SegPrefZoneSet`` Place the segment in specified zones.
``SegPrefHigh`` Prefer high addresses.
``SegPrefLow`` Prefer low addresses.
``SegPrefZoneSet`` Prefer addresses in specified zones.
================== ====================================================
.. note::
The name is misleading as this is used to refer to address
preferences in general, not just addresses of segments.
``typedef unsigned Serial``
@ -490,9 +504,8 @@ _`.serial`: A ``Serial`` is a number which is assigned to a structure
when it is initialized. The serial number is taken from a field in the
parent structure, which is incremented. Thus, every instance of a
structure has a unique "name" which is a path of structures from the
global root. For example::
space[3].pool[5].buffer[2]
global root. For example, "the third arena's fifth pool's second
buffer".
Why? Consistency checking, debugging, and logging. Not well thought
out.
@ -509,6 +522,8 @@ right-hand operand of the ``<<`` or ``>>`` operators) is intended, to
make the code clear. It should also be used for structure fields which
have this use.
.. note:: Could ``Shift`` be an ``unsigned short`` or ``unsigned char``?
``typedef unsigned long Sig``
@ -640,7 +655,7 @@ _`.word.ops`: ``WordIsAligned()``, ``WordAlignUp()``,
``typedef Word ZoneSet``
_`.zoneset`: ``ZoneSet`` is a conservative approximation to a set of
zone. See design.mps.refset_.
zones. See design.mps.refset_.
Abstract types