[mercury-users] Why isn't deforestation working here?

[Ralph Becket]

I've attached the simplified code for the LZW compression module I've been
working on.  I've got several successive refinements of this thing (the
attached version isn't one of the scarier ones), but all share pretty much
the same main-loop code.  I've managed to get rid of just about all memory
allocation in the program, but there is one place left that is bugging me,
and it's to do with io__result/1s being generated every time my program
reads a byte from the input file.

The basic format of the code is something like this:

	io__read_byte(Result, IO_in, IO_out),
	(	Result = ok(Byte), ...
	;	Result = eof, ...
	;	Result = error(ErrCode), ...
	)

and I was under the impression that compiling with

	MCFLAGS = -O 6 --intermodule-optimization

should deforest (vb?) this code.  Any help would be greatly appreciated!

Cheers,

Ralph


begin 600 compress.m
M)2`M+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM
M+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM("4*)2!C;VUP<F5S
M<RYM"B4*)2!697)S:6]N(#$*)0HE(%1H:7,@=F5R<VEO;B!I<R!A8F]U="!A
M<R!S:6UP;&4 at 87,@:70 at 9V5T<RP@=7-I;F<@=&AE('-T86YD87)D(&QI8G)A
M<GD*)2!M87`@*&$@,C,T('1R964@:6UP;&5M96YT871I;VXI('1O(&UA<"!P
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M(&ME97!I;F<@86QL('1H92!B:6YA<GD@;W5T<'5T('-T=69F(&QO8VME9"!I
M;B!A('-I;F=L92T*)2!C;VYS=')U8W1O<B!T>7!E+ at HE"B4 at +2TM+2TM+2TM
M+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM
M+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2`E"@HZ+2!M;V1U;&4 at 8V]M<')E<W,N
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M+2TM("4*)2`M+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM+2TM
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`
end
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