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Provide a mechanism to allow a predicate to be defined as a foreign_proc for
one backend and as external for another backend. The intended use is to
implement builtin_catch in exception.m, which cannot be implemented as a
foreign_proc for hlc grades, but whose implementation as external for the
LLDS grades requires handwriting extremely error-prone code and data structures
that the compiler could generate reliably.
The mechanism is two language extensions. One allows :- external declarations
such as
:- external(high_level_backend, p/3).
The second allows foreign_procs such as
:- pragma foreign_proc("C",
p(N::in, IO0::di, IO::uo),
[will_not_call_mercury, promise_pure, low_level_backend],
...
compiler/prog_data.m:
Add an extra field to the items for `:- external' declarations to
allow hold the optional backend designation.
Add an extra optional attribute to foreign_procs to handle the
backend designation.
compiler/prog_io_pragma.m:
Change the code for reading external declarations to handle the new
attribute.
compiler/prog_io_pragma.m:
Change the code for reading foreign_proc attributes to handle the new
attribute.
compiler/make_hlds.m:
Ignore external declarations and foreign_proc definitions if they are
for the wrong backend.
Use state variables in a place that can benefit from it.
compiler/hlds_module.m:
Clean up some formatting.
compiler/equiv_type.m:
compiler/ml_code_gen.m:
compiler/module_qual.m:
compiler/modules.m:
Conform to the changed data structures in prog_data.
doc/reference_manual.texi:
Add commented-out documentation of the extension to foreign_procs.
There is no existing documentation of :- external to update.
tests/hard_coded/backend_external.{m,exp,exp2}:
New test case for the new language extensions.
tests/hard_coded/Mmakefile:
Enable the new test case.
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3 lines
88 B
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p(1): expected lowlevel, found lowlevel, OK
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q(2): expected lowlevel, found lowlevel, OK
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