[m-rev.] for review: fix delay death and parallel conjunctions

[Julien Fischer]

On Fri, 30 Jun 2006, Peter Wang wrote:

> Estimated hours taken: 6
> Branches: main
>
> compiler/liveness.m:
> 	Fix the deadness pass's handling of parallel conjunctions.

The log message should mention what was wrong with it.

> 	This was causing problems with later passes (delay death and resume
> 	point detection) because variables were appearing in the pre-death
> 	and post-death sets that they shouldn't have.
>
> 	Also make detect_deadness_in_par_conj look more similar to
> 	detect_deadness_in_disj and detect_deadness_in_cases.

Is this just a cosmetic change?

> 	Revert the previous change to delay_death_par_conj which was
> 	unnecessary and caused problems with nested parallel conjunctions and
> 	--delay-death.
>
> tests/par_conj/Mercury.options:
> tests/par_conj/Mmakefile:
> tests/par_conj/par_ddeath.exp:
> tests/par_conj/par_ddeath.m:
> tests/par_conj/par_ddeath_2.exp:
> tests/par_conj/par_ddeath_2.m:
> 	Add test cases.
>
>

...

> retrieving revision 1.1
> diff -u -r1.1 Mercury.options
> --- tests/par_conj/Mercury.options	28 Jun 2006 06:13:12 -0000	1.1
> +++ tests/par_conj/Mercury.options	30 Jun 2006 04:38:04 -0000
> @@ -0,0 +1,2 @@
> +MCFLAGS-par_ddeath = --trace deep
> +MCFLAGS-par_ddeath_2 = --trace deep

I would put a short comment there explaining why those test cases need to
be compiled with deep tracing, e.g

	# These test cases are compiled with --trace deep because they
	# are regression tests for a bug that only shows up with deep
	# tracing.

...

> Index: tests/par_conj/par_ddeath.m
> ===================================================================
> RCS file: tests/par_conj/par_ddeath.m
> diff -N tests/par_conj/par_ddeath.m
> --- /dev/null	1 Jan 1970 00:00:00 -0000
> +++ tests/par_conj/par_ddeath.m	30 Jun 2006 11:42:42 -0000
> @@ -0,0 +1,30 @@
> +% There was a problem with this file when --trace deep was used,
> +% due to a bug in the --delay-death pass.
> +%
> +% Uncaught Mercury exception:
> +% Software Error: map.lookup: key not found
> +%         Key Type: term.var(parse_tree.prog_data.prog_var_type)
> +%         Key Value: var(6)
> +%         Value Type: ll_backend.var_locn.var_state
> +

I find it helpful if the comments at the head of regression tests explain
what the cause of the bug was.

The rest of that looks okay.

Julien.
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