[m-rev.] diff: fix bug in mode analysis wrt quantification
Zoltan Somogyi
zs at cs.mu.OZ.AU
Fri Oct 7 14:33:17 AEST 2005
For review by Ralph.
Zoltan.
Fix a bug I detected and Ralph tracked down. It was the result of an
interaction of the state variable transformation, mode analysis and
(lack of) quantification.
Sometimes, the final value of a state variable introduced with "some [!X]"
notation is not used along some paths of computation. In some of those cases,
a second pass of mode checking (usually unique mode checking) could delete the
unification building the final version of the state variable in one branch
of e.g. a switch while not being able to delete a procedure call building
that same final version transformation in another branch. Later compiler passes
then get errors because the branches bind different sets of variables.
The fix is to rerun quantification when this happens, to delete the final
version of the state variable from the switch's nonlocal set and thus from
the nonlocal set of any non-eliminated goals that bind it.
compiler/mode_info.m:
Add a field to the mode info that records the need for a
requantification.
compiler/modecheck_unify.m:
When eliminating a unification, set the flag if the unification was
inserted by the state variable transformation and may contain a
singleton variable (such as the final version of the variable in the
example above).
compiler/modes.m:
Requantify the procedure at the end of mode analysis if the flag
is set.
tests/valid/state_var_mode_bug.m:
New test case, a very cut down and abstracted version of the original
code the bug was detected in.
tests/valid/Mmakefile:
Enable the new test case.
cvs diff: Diffing .
cvs diff: Diffing analysis
cvs diff: Diffing bindist
cvs diff: Diffing boehm_gc
cvs diff: Diffing boehm_gc/Mac_files
cvs diff: Diffing boehm_gc/cord
cvs diff: Diffing boehm_gc/cord/private
cvs diff: Diffing boehm_gc/doc
cvs diff: Diffing boehm_gc/include
cvs diff: Diffing boehm_gc/include/private
cvs diff: Diffing boehm_gc/tests
cvs diff: Diffing browser
cvs diff: Diffing bytecode
cvs diff: Diffing compiler
Index: compiler/mode_info.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/compiler/mode_info.m,v
retrieving revision 1.74
diff -u -b -r1.74 mode_info.m
--- compiler/mode_info.m 30 Sep 2005 08:08:27 -0000 1.74
+++ compiler/mode_info.m 6 Oct 2005 06:09:20 -0000
@@ -121,6 +121,7 @@
:- pred mode_info_get_errors(mode_info::in, list(mode_error_info)::out) is det.
:- pred mode_info_get_warnings(mode_info::in, list(mode_warning_info)::out)
is det.
+:- pred mode_info_get_need_to_requantify(mode_info::in, bool::out) is det.
:- pred mode_info_get_num_errors(mode_info::in, int::out) is det.
:- pred mode_info_get_liveness(mode_info::in, set(prog_var)::out) is det.
:- pred mode_info_get_varset(mode_info::in, prog_varset::out) is det.
@@ -168,6 +169,8 @@
mode_info::in, mode_info::out) is det.
:- pred mode_info_set_warnings(list(mode_warning_info)::in,
mode_info::in, mode_info::out) is det.
+:- pred mode_info_set_need_to_requantify(bool::in,
+ mode_info::in, mode_info::out) is det.
:- pred mode_info_add_live_vars(set(prog_var)::in,
mode_info::in, mode_info::out) is det.
:- pred mode_info_remove_live_vars(set(prog_var)::in,
@@ -240,6 +243,8 @@
:- pred mode_info_add_warning(mode_warning_info::in,
mode_info::in, mode_info::out) is det.
+:- pred mode_info_need_to_requantify(mode_info::in, mode_info::out) is det.
+
%-----------------------------------------------------------------------------%
% The mode_info contains a flag indicating whether initialisation calls,
@@ -309,7 +314,11 @@
initial_instmap :: instmap,
% The mode warnings found.
- warnings :: list(mode_warning_info)
+ warnings :: list(mode_warning_info),
+
+ % Set to `yes' if we need to requantify the procedure body
+ % after mode analysis finishes.
+ need_to_requantify :: bool
).
:- type mode_info
@@ -433,9 +442,10 @@
Changed = no,
CheckingExtraGoals = no,
MayInitSolverVars = yes,
+ NeedToRequantify = no,
ModeSubInfo = mode_sub_info(ProcId, VarSet, Unreachable, Changed,
- CheckingExtraGoals, InstMapping0, WarningList),
+ CheckingExtraGoals, InstMapping0, WarningList, NeedToRequantify),
ModeInfo = mode_info(ModuleInfo, PredId, VarTypes, Debug,
Context, ModeContext, InstMapping0, LockedVars, DelayInfo,
@@ -457,6 +467,7 @@
mode_info_get_locked_vars(MI, MI ^ locked_vars).
mode_info_get_errors(MI, MI ^ errors).
mode_info_get_warnings(MI, MI ^ mode_sub_info ^ warnings).
+mode_info_get_need_to_requantify(MI, MI ^ mode_sub_info ^ need_to_requantify).
mode_info_get_delay_info(MI, MI ^ delay_info).
mode_info_get_live_vars(MI, MI ^ live_vars).
mode_info_get_nondet_live_vars(MI, MI ^ nondet_live_vars).
@@ -479,6 +490,8 @@
mode_info_set_errors(Errors, MI, MI ^ errors := Errors).
mode_info_set_warnings(Warnings, MI,
MI ^ mode_sub_info ^ warnings := Warnings).
+mode_info_set_need_to_requantify(NTRQ, MI,
+ MI ^ mode_sub_info ^ need_to_requantify := NTRQ).
mode_info_set_delay_info(DelayInfo, MI, MI ^ delay_info := DelayInfo).
mode_info_set_live_vars(LiveVarsList, MI, MI ^ live_vars := LiveVarsList).
mode_info_set_nondet_live_vars(NondetLiveVars, MI,
@@ -699,6 +712,9 @@
mode_info_get_warnings(!.ModeInfo, Warnings0),
list__append(Warnings0, [ModeWarningInfo], Warnings),
mode_info_set_warnings(Warnings, !ModeInfo).
+
+mode_info_need_to_requantify(!ModeInfo) :-
+ mode_info_set_need_to_requantify(yes, !ModeInfo).
%-----------------------------------------------------------------------------%
Index: compiler/modecheck_unify.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/compiler/modecheck_unify.m,v
retrieving revision 1.88
diff -u -b -r1.88 modecheck_unify.m
--- compiler/modecheck_unify.m 5 Oct 2005 06:33:47 -0000 1.88
+++ compiler/modecheck_unify.m 6 Oct 2005 06:09:20 -0000
@@ -88,8 +88,8 @@
%-----------------------------------------------------------------------------%
-modecheck_unification(X, var(Y), Unification0, UnifyContext,
- UnifyGoalInfo0, Unify, !ModeInfo, !IO) :-
+modecheck_unification(X, var(Y), Unification0, UnifyContext, UnifyGoalInfo0,
+ Unify, !ModeInfo, !IO) :-
mode_info_get_module_info(!.ModeInfo, ModuleInfo0),
mode_info_get_var_types(!.ModeInfo, VarTypes),
mode_info_get_instmap(!.ModeInfo, InstMap0),
@@ -149,7 +149,8 @@
ModeOfX = (InstOfX -> Inst),
ModeOfY = (InstOfY -> Inst),
categorize_unify_var_var(ModeOfX, ModeOfY, LiveX, LiveY, X, Y,
- Det, UnifyContext, VarTypes, Unification0, Unify0, !ModeInfo),
+ Det, UnifyContext, UnifyGoalInfo0, VarTypes, Unification0, Unify0,
+ !ModeInfo),
(
MaybeInitX = no,
Unify = Unify0
@@ -834,12 +835,12 @@
%
:- pred categorize_unify_var_var((mode)::in, (mode)::in,
is_live::in, is_live::in, prog_var::in,
- prog_var::in, determinism::in, unify_context::in,
+ prog_var::in, determinism::in, unify_context::in, hlds_goal_info::in,
map(prog_var, type)::in, unification::in, hlds_goal_expr::out,
mode_info::in, mode_info::out) is det.
categorize_unify_var_var(ModeOfX, ModeOfY, LiveX, LiveY, X, Y, Det,
- UnifyContext, VarTypes, Unification0, Unify, !ModeInfo) :-
+ UnifyContext, GoalInfo, VarTypes, Unification0, Unify, !ModeInfo) :-
mode_info_get_module_info(!.ModeInfo, ModuleInfo0),
(
mode_is_output(ModuleInfo0, ModeOfX)
@@ -889,7 +890,7 @@
UnifyContext, Unification0, Unification, !ModeInfo)
)
),
- %
+
% Optimize away unifications with dead variables and simple tests that
% cannot fail by replacing them with `true'. (The optimization of simple
% tests is necessary because otherwise determinism analysis assumes they
@@ -898,17 +899,18 @@
%
% Optimize away unifications which always fail by replacing them with
% `fail'.
- %
(
Unification = assign(AssignTarget, _),
mode_info_var_is_live(!.ModeInfo, AssignTarget, dead)
->
- Unify = conj([])
+ Unify = conj([]),
+ record_optimize_away(GoalInfo, !ModeInfo)
;
Unification = simple_test(_, _),
Det = det
->
- Unify = conj([])
+ Unify = conj([]),
+ record_optimize_away(GoalInfo, !ModeInfo)
;
Det = failure
->
@@ -935,6 +937,16 @@
)
;
Unify = unify(X, var(Y), ModeOfX - ModeOfY, Unification, UnifyContext)
+ ).
+
+:- pred record_optimize_away(hlds_goal_info::in,
+ mode_info::in, mode_info::out) is det.
+
+record_optimize_away(GoalInfo, !ModeInfo) :-
+ ( goal_info_has_feature(GoalInfo, dont_warn_singleton) ->
+ mode_info_need_to_requantify(!ModeInfo)
+ ;
+ true
).
% Modecheck_complicated_unify does some extra checks that are needed
Index: compiler/modes.m
===================================================================
RCS file: /home/mercury/mercury1/repository/mercury/compiler/modes.m,v
retrieving revision 1.315
diff -u -b -r1.315 modes.m
--- compiler/modes.m 5 Oct 2005 06:33:48 -0000 1.315
+++ compiler/modes.m 6 Oct 2005 06:09:20 -0000
@@ -361,6 +361,7 @@
:- import_module hlds__instmap.
:- import_module hlds__make_hlds.
:- import_module hlds__passes_aux.
+:- import_module hlds__quantification.
:- import_module hlds__special_pred.
:- import_module libs__globals.
:- import_module libs__options.
@@ -943,10 +944,17 @@
% VarTypes may be the same as VarTypes0, since mode checking can
% add new variables (e.g. when handling calls in implied modes).
mode_info_get_var_types(!.ModeInfo, VarTypes),
+ mode_info_get_need_to_requantify(!.ModeInfo, NeedToRequantify),
proc_info_set_goal(Body, !ProcInfo),
proc_info_set_varset(VarSet, !ProcInfo),
proc_info_set_vartypes(VarTypes, !ProcInfo),
- proc_info_set_argmodes(ArgModes, !ProcInfo)
+ proc_info_set_argmodes(ArgModes, !ProcInfo),
+ (
+ NeedToRequantify = no
+ ;
+ NeedToRequantify = yes,
+ requantify_proc(!ProcInfo)
+ )
).
%-----------------------------------------------------------------------------%
cvs diff: Diffing compiler/notes
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cvs diff: Diffing debian/patches
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cvs diff: Diffing tests/hard_coded/purity
cvs diff: Diffing tests/hard_coded/sub-modules
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cvs diff: Diffing tests/invalid
cvs diff: Diffing tests/invalid/purity
cvs diff: Diffing tests/misc_tests
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Index: tests/valid/Mmakefile
===================================================================
RCS file: /home/mercury/mercury1/repository/tests/valid/Mmakefile,v
retrieving revision 1.157
diff -u -b -r1.157 Mmakefile
--- tests/valid/Mmakefile 16 Aug 2005 05:17:07 -0000 1.157
+++ tests/valid/Mmakefile 6 Oct 2005 03:15:48 -0000
@@ -186,6 +186,7 @@
stack_alloc \
stack_opt_simplify \
state_var_bug \
+ state_var_mode_bug \
static \
subtype_switch \
switch_detection_bug \
Index: tests/valid/state_var_mode_bug.m
===================================================================
RCS file: tests/valid/state_var_mode_bug.m
diff -N tests/valid/state_var_mode_bug.m
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ tests/valid/state_var_mode_bug.m 7 Oct 2005 04:18:52 -0000
@@ -0,0 +1,97 @@
+%-----------------------------------------------------------------------------%
+% vim: ft=mercury ts=4 sw=4 et
+%-----------------------------------------------------------------------------%
+%
+% Author: Ralph Becket <rafe at cs.mu.oz.au>
+%
+% This is a regression test for a bug involving the interaction of the mode
+% system and quantification, triggered by the state variable transformation.
+%
+%-----------------------------------------------------------------------------%
+
+:- module state_var_mode_bug.
+
+:- interface.
+
+:- import_module bool, int.
+
+:- pred p(bool::in, bool::in, int::in, int::out) is semidet.
+
+:- implementation.
+
+p(A, B, !Y) :-
+ some [!X] (
+ p0(!:X),
+ p2(!X),
+ p2(!X),
+ (
+ A = yes
+ ->
+ (
+ B = yes,
+ p1(!.X),
+ p2(!X),
+ p1(!.X)
+ ;
+ B = no,
+ (
+ p1(!.X),
+ p2(!X)
+ ->
+ p1(!.X)
+ ;
+ true
+ )
+ )
+ ;
+ (
+ p1(!.X),
+ p2(!X)
+ ->
+ (
+ A = yes,
+ p1(!.X),
+ p2(!X),
+ % The bug occurs here. The final value of !X is defined
+ % in both branches of this switch, but this final value
+ % is not used. The unique modes can therefore optimize away
+ % the copy unification in the "no" branch, but cannot
+ % optimize away the binding of the variable representing
+ % the value in the call to p2 in the "yes" branch. Later
+ % compiler passes that check whether the two branches bind
+ % the same set of variables in the process of recomputing
+ % instmap delta then find that they don't, leading to a
+ % compiler abort.
+ (
+ B = yes,
+ p2(!X)
+ ;
+ B = no
+ )
+ ;
+ A = no
+ )
+ ;
+ p1(!.X)
+ ->
+ p1(!.X),
+ p2(!X),
+ p1(!.X)
+ ;
+ true
+ )
+ )
+ ).
+
+:- pred p0(int::out) is det.
+
+p0(0).
+
+:- pred p1(int::in) is semidet.
+
+p1(1).
+
+:- pred p2(int::in, int::out) is semidet.
+
+p2(!X) :-
+ p1(!.X).
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cvs diff: Diffing vim
cvs diff: Diffing vim/after
cvs diff: Diffing vim/ftplugin
cvs diff: Diffing vim/syntax
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