Construction unifications of partially instantiated values involving direct
argument functors (where the single argument is free) did not generate any code
in both low-level and high-level backends. Incorrect behaviour could result if
the program tried to deconstruct the value at run-time.
Also, in the LLDS backend, such a construction unification did not enter the
variable into the var_state_map, leading to a compiler abort when the variable
is looked up.
compiler/ml_unify_gen.m:
Generate code for constructions of a direct arg functor with free
argument. This amounts to assigning a variable to a tagged null
pointer.
compiler/llds.m:
Add an rval option `mkword_hole', which is like `mkword' but the
pointer to be tagged is unspecified.
compiler/unify_gen.m:
Assign a variable to an `mkword_hole' rval, for a construction
unification of a direct arg functor with a free argument.
Reassign the variable to an `mkword' rval when the argument becomes
bound in a later unification.
compiler/code_info.m:
compiler/var_locn.m:
Add a predicate to reassign a variable from a `mkword_hole' expression
to a `mkword' expression.
compiler/llds_out_data.m:
Write out `mkword_hole' values as a tagged null pointer in C code.
compiler/call_gen.m:
compiler/code_util.m:
compiler/dupelim.m:
compiler/dupproc.m:
compiler/exprn_aux.m:
compiler/global_data.m:
compiler/jumpopt.m:
compiler/livemap.m:
compiler/llds_to_x86_64.m:
compiler/middle_rec.m:
compiler/opt_debug.m:
compiler/opt_util.m:
compiler/peephole.m:
compiler/stack_layout.m:
Conform to addition of `mkword_hole'.
tests/hard_coded/Mmakefile:
tests/hard_coded/direct_arg_partial_inst.exp:
tests/hard_coded/direct_arg_partial_inst.m:
tests/hard_coded/direct_arg_partial_inst2.exp:
tests/hard_coded/direct_arg_partial_inst2.m:
Add test cases.
