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dc03496d06
Estimated hours taken: 130
Rewrite significant parts of minimal model tabling so that it works
in a much wider variety of situations, including coups. Also, clean up
the tabling implementation to make it more maintainable, and introduce
a new grade component, .mm, that enables minimal model tabling.
(Minimal model tabling requires distributed fat, and we don't want to
incur such costs unless necessary.)
compiler/options.m:
Add a new option --use-minimal-model, which for now is documented
as "not for general use". This option is a grade option, and is
required if minimal model tabling is to work.
compiler/handle_options.m:
When --use-minimal-model is given, do not allow nondet frame hijacks,
since minimal model tabling cannot cope with hijacks.
Make --use-minimal-model a grade component.
compiler/code_info.m:
When --use-minimal-model is given, insert calls to MR_commit_{mark,cut}
around goals being committed across. This is now necessary, so that we
can detect and handle sitations where a goal being committed across
starts but does not complete a tabled goal.
compiler/table_gen.m:
Rename many of the tabling helper predicates, using a naming scheme
that separates predicates used for model_non procedures from those
used to implement simpler forms of tabling, while bringing out
the parallels between these two sets of predicates.
When calls to two tabling helper predicates always occur
one after the other, merge the two into one.
Generate and use more meaningful variable names; having all of the
several variables inserted by this transformation named TableVar
was quite confusing.
library/private_builtin.m:
Reorganize this file, to separate out the different sections.
The contents of the non-tabling sections were not modified, only
moved around.
Rename the predicates referred to by table_gen.m.
Move most of the type declarations and complex code out of here,
into runtime/mercury_tabling.c. This makes it easier to debug them,
since (a) creating a new executable is quicker, since you don't have
to wait for lots of mercury compiler invocations, and (b) gdb doesn't
get confused by #line directives. It also makes it easier to write
them, since you don't have to !&(*U&( remember to double all your
double quotes and to backslash all your backslashes.
runtime/mercury_grade.h:
Include a grade component reflecting whether MR_USE_MINIMAL_MODEL
is defined.
runtime/mercury_conf_param.h:
Document MR_USE_MINIMAL_MODEL.
runtime/mercury_stacks.[ch]:
The changes to tabling require the addition of two new stacks,
the generator stack and the cut stack. This module defines the
structures of the frames of these stacks and provides the
operations on these stacks.
The header file also contains some additional macros that return
the addresses of fixed nondet stack slots, not their contents,
for use by tabling code.
runtime/mercury_context.[ch]:
runtime/mercury_memory.[ch]:
runtime/mercury_wrapper.[ch]:
Declare and set up the two new stacks, both in saved contexts and in
the active context, if MR_USE_MINIMAL_MODEL is defined.
runtime/mercury_regorder.h:
Add four new global virtual machine registers to hold pointers
to the memory areas of the two new stacks and the current offsets
within them. These are defined whether MR_USE_MINIMAL_MODEL is defined
or not, since the cost is minimal and the potential bugs we avoid
would be hard to track down.
runtime/mercury_engine.h:
runtime/mercury_wrapper.c:
Add support for a new debugging flag, -dS, which prints the contents
of the nondet stack at several points during tabling.
runtime/mercury_tabling.[ch]:
The implementation of the new tabling system. Much of the new code here
is stuff moved from library/private_builtin.m, but in a significantly
rewritten form. There is also substantial new code, e.g. to handle
the extension of saved stack segments, and to manage dependencies
between subgoals in general.
Improve the documentation considerably.
Replace lists stored as Mercury data structures with lists stored
as linked structures in the usual C fashion. This allows us to use
debuggers such as ddd on these data structures, whose complexity
requires this.
Ensure that global names start with MR_.
runtime/mercury_init.h:
Explicitly include mercury_regs.h at the start. Without this,
we get an error, because now mercury_wrappers.h, which mercury_init.h
includes, also includes mercury_regs.h, but not before functions
have been declared.
runtime/Mmakefile:
Refer to the new file mercury_stacks.c (mercury_stacks.h already
existed, but the module consisted entirely of macros.)
Fix a sorting error.
scripts/{init,parse,final}_grade_options.sh-subr:
scripts/mgnuc.in:
Handle the new grade component.
tests/tabling/*
Add several new test cases that we now pass, most of which we couldn't
pass before. Also add some new test cases that we don't pass yet,
due to interactions between tabling and negated contexts.
trace/mercury_trace_internal.c:
If MR_USE_MINIMAL_MODEL is defined, add a new command to print
the generator stack. (The new command is deliberately not documented
in doc/mdb_doc yet, since (a) it is intended for developers only,
and (b) there is no way to test MR_USE_MINIMAL_MODEL in mdb_doc.)