performance bug

[Simon TAYLOR]

On mercury-bugs, Fergus wrote:
> There is a bug with intermodule optimization: it is including
> lots of dead code in the generated .c files, for functions
> which are defined in other modules but never used.
> For example, the text size of library/library.o is about 50k, whereas
> it ought to be less than 1k.

This is caused by using the wrong version of a module_info
in dead_proc_elim.m.

There is a performance problem with inter-module optimization in that 
it performs analysis on all predicates imported from `.opt' files,
not just the ones that are used in the current module. I'll fix that 
one soon.


Estimated hours taken: 0.5

compiler/dead_proc_elim.m
	Dead procedure elimination was claiming to remove dead procedures 
	but wasn't actually removing them due to using the wrong version 
	of a module_info.

Index: dead_proc_elim.m
===================================================================
RCS file: /home/staff/zs/imp/mercury/compiler/dead_proc_elim.m,v
retrieving revision 1.28
diff -u -r1.28 dead_proc_elim.m
--- dead_proc_elim.m	1997/06/12 04:23:07	1.28
+++ dead_proc_elim.m	1997/06/17 04:19:03
@@ -440,7 +440,7 @@
 	module_info_base_gen_infos(ModuleInfo2, BaseGenInfos0),
 	dead_proc_elim__eliminate_base_gen_infos(BaseGenInfos0, Needed,
 		BaseGenInfos),
-	module_info_set_base_gen_infos(ModuleInfo1, BaseGenInfos, ModuleInfo).
+	module_info_set_base_gen_infos(ModuleInfo2, BaseGenInfos, ModuleInfo).
 
 
 		% eliminate any unused procedures for this pred