[m-rev.] for review: Opt-export version_array lookup and set.

[Peter Wang]

This allows the compiler to eliminate the construction of typeinfo
arguments for calls to version_array.lookup and version_array.set,
when compiling with intermodule optimisation and --optimize-unused-args.

In particular, version_hash_table would previously dynamically construct
typeinfos in order lookup or update hash table buckets.

This change improves the run time of a do-nothing build of Prince using
mmc --make on my machine from 1.6 s to 1.43 s.

library/version_array.m:
    Add pragma inlines for version_array.lookup and version_array.set.

library/Mercury.options:
    Always compile version_hash_table with --optimize-unused-args.

diff --git a/library/Mercury.options b/library/Mercury.options
index 0e828c1a9..6a621788a 100644
--- a/library/Mercury.options
+++ b/library/Mercury.options
@@ -21,6 +21,8 @@ MCFLAGS-lexer                   += --optimize-constructor-last-call
 MCFLAGS-sparse_bitset   += --use-atomic-cells --optimize-constant-propagation
 MCFLAGS-tree_bitset     += --use-atomic-cells --optimize-constant-propagation
 
+MCFLAGS-version_hash_table      += --optimize-unused-args
+
 # Speed up structure sharing analysis.
 MCFLAGS-set_ctree234            += --structure-sharing-widening 1
 MCFLAGS-set_tree234             += --structure-sharing-widening 1
diff --git a/library/version_array.m b/library/version_array.m
index 463bf89e8..0e2d36955 100644
--- a/library/version_array.m
+++ b/library/version_array.m
@@ -461,6 +461,7 @@ from_reverse_list_loop(I, [X | Xs], !VA) :-
 lookup(VA, I) = X :-
     lookup(VA, I, X).
 
+:- pragma inline(pred(version_array.lookup/3)).
 lookup(VA, I, X) :-
     ( if get_if_in_range(VA, I, X0) then
         X = X0
@@ -474,6 +475,7 @@ VA ^ elem(I) = X :-
 
 %---------------------------------------------------------------------------%
 
+:- pragma inline(pred(version_array.set/4)).
 set(I, X, !VA) :-
     ( if set_if_in_range(I, X, !VA) then
         true
-- 
2.38.0