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mercury/compiler/code_gen.m
Zoltan Somogyi d1855187e5 Implement new methods of handling failures and the end points of branched 
Estimated hours taken: 260

Implement new methods of handling failures and the end points of branched
control structures.

compiler/notes/failure.html:
	Fix an omission about the handling of resume_is_known in if-then-elses.
	(This omission lead to a bug in the implementation.)

	Optimize cuts across multi goals when curfr is known to be equal
	to maxfr.

	Clarify the wording in several places.

compiler/code_info.m:
	Completely rewrite the methods for handling failure.

	Separate the fields of code_info into three classes: those which
	do not change after initialization, those which record state that
	depends on where in the HLDS goal we are, and those which contain
	persistent data such as label and cell counters.

	Rename grab_code_info and slap_code_info as remember_position
	and reset_to_position, and add a wrapper around the remembered
	code_info to make it harder to make mistakes in its use.
	(Only the location-dependent fields of the remembered code_info
	are used, but putting only them into a separate data structure would
	result in more, not less, memory being allocated.)

	Gather the predicates that deal with handling branched control
	structures into a submodule.

	Reorder the declarations and definitions of access predicates
	to conform to the new order of fields.

	Reorder the declarations and definitions of the failure handling
	submodule to better reflect the separation of higher-level and
	lower-level predicates.

compiler/code_gen.m:
	Replace code_gen__generate_{det,semi,non}_goal_2 with a single
	predicate, since for most HLDS constructs the code here is the same
	anyway (the called preds check the code model when needed).

	Move classification of the various kinds of unifications to unify_gen,
	since that is where it belongs.

	Move responsibility for initializing the code generator's trace
	info to code_info.

	Move the generation of code for negations to ite_gen, since the
	handling of negations is a cut-down version of the handling of
	negations. This should make the required double maintenance easier,
	and more likely to happen.

compiler/disj_gen.m:
compiler/ite_gen.m:
	These are the two modules that handle most failures; they have
	undergone a significant rewrite. As part of this rewrite, factor
	out the remaining common code between model_non and model_{det,semi}
	goals.

compiler/unify_gen.m:
	Move classification of the various kinds of unifications here from
	code_gen. This allows us to keep several previously exported
	predicates private.

compiler/call_gen.m:
	Factor out some code that was common to ordinary calls, higher order
	calls and method calls. Move the common code that checks whether
	we are doing tracing to trace.m.

	Replace call_gen__generate_{det,semi,nondet}_builtin with a single
	predicate.

	Delete the commented out call_gen__generate_complicated_unify,
	since it will never be needed and in any case suffered from
	significant code rot.

compiler/llds.m:
	Change the mkframe instruction so that depending on one of its
	arguments, it can create either ordinary frames, or the cut-down
	frames used by the new failure handling algorithm (they have only
	three fixed fields: prevfr, redoip and redofr).

compiler/llds_out.m:
	Emit a #define MR_USE_REDOFR before including mercury_imp.h, to
	tell the runtime we are using the new failure handling scheme.
	This effectively changes the grade of the compiled module.

	Emit MR_stackvar and MR_framevar instead of detstackvar and framevar.
	This is a step towards cleaning up the name-space, and a step towards
	making both start numbering at 0. For the time being, the compiler
	internally still starts counting framevars at 0; the code in llds_out.m
	adds a +1 offset.

compiler/trace.m:
	Change the way trace info is initialized to fit in with the new
	requirements of code_info.m.

	Move the "are we tracing" check from the callers to the implementation
	of trace__prepare_for_call.

compiler/*.m:
	Minor changes in accordance with the major ones above.

compiler/options.m:
	Introduce a new option, allow_hijacks, which is set to "yes" by
	default. It is not used yet, but the idea is that when it is set to no,
	the code generator will not generate code that hijacks the nondet
	stack frame of another procedure invocation; instead, it will create
	a new temporary nondet stack frame. If the current procedure is
	model_non, it will have three fields: prevfr, redoip and redofr.
	If the current procedure is model_det or model_semi, it will have
	a fourth field that is set to the value of MR_sp. The idea is that
	the runtime system, which will be able to distinguish between
	ordinary frames (whose size is at least 5 words), 3-word and 4-word
	temporary frames, will now be able to use the redofr slots of
	all three kinds of frames and the fourth slot values of 4-word
	temporary frames as the addresses relative to which framevars
	and detstackvars respectively ought to be offset in stack layouts.

compiler/handle_options.m:
	Turn off allow_hijacks if the gc method is accurate.

runtime/mercury_stacks.h:
	Change the definitions for the nondet stack handling macros
	to accommodate the new nondet stack handling discipline.
	Define a new macro for creating temp nondet frames.

	Define MR_based_stackvar and MR_based_framevar (both of which start
	numbering slots at 1), and express other references, including
	MR_stackvar and MR_framevar and backward compatible definitions of
	detstackvar and framevar for hand-written C code, in terms of those
	two.

runtime/mercury_stack_trace.[ch]:
	Add a new function to print a dump of the fixed elements nondet stack,
	for debugging my changes. (The dump does not include variable values.)

runtime/mercury_trace_internal.c:
	Add a new undocumented command "D" for dumping the nondet stack
	(users should not know about this command, since the output is
	intelligible only to implementors).

	Add a new command "toggle_echo" that can cause the debugger to echo
	all commands. When the input to the debugger is redirected, this
	echo causes the output of the session to be much more readable.

runtime/mercury_wrapper.c:
	Save the address of the artificial bottom nondet stack frame,
	so that the new function in mercury_stack_trace.c can find out
	where to stop.

runtime/mercury_engine.c:
runtime/mercury_wrapper.c:
	Put MR_STACK_TRACE_THIS_MODULE at the tops of these modules, so that
	the labels they define (e.g. do_fail and global_success) are registered
	in the label table when their module initialization functions are
	called. This is necessary for a meaningful nondet stack dump.

runtime/mercury_grade.h:
	Add a new component to the grade string that specifies whether
	the code was compiled with the old or the new method of handling
	the nondet stack. This is important, because modules compiled
	with different nondet stack handling disciplines are not compatible.
	This component depends on whether MR_USE_REDOFR is defined or not.

runtime/mercury_imp.h:
	If MR_DISABLE_REDOFR is defined, undefine off MR_USE_REDOFR before
	including mercury_grade.h. This is to allow people to continue
	working on un-updated workspaces after this change is installed;
	they should put "EXTRA_CFLAGS = -DMR_DISABLE_REDOFR" into
	Mmake.stage.params. (This way their stage1 will use the new method
	of handling failure, while their stage2 2&3 will use the old one.)

	This change should be undone once all our workspaces have switched
	over to the new failure handling method.

tests/hard_coded/cut_test.{m,exp}:
	A new test case to tickle the various ways of handling cuts in the
	new code generator.

tests/hard_coded/Mmakefile:
	Enable the new test case.
1998-07-20 10:04:02 +00:00

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%---------------------------------------------------------------------------%
% Copyright (C) 1994-1998 The University of Melbourne.
% This file may only be copied under the terms of the GNU General
% Public License - see the file COPYING in the Mercury distribution.
%---------------------------------------------------------------------------%
%
% Code generation - convert from HLDS to LLDS.
%
% Main authors: conway, zs.
%
% The two main tasks of this module are
%
% 1 to look after the aspects of generating code for a procedure
% that do not involve generating code for a specific goal, and
%
% 2 to provide a generic predicate that can be called from anywhere in
% the code generator to generate code for a goal.
%
% Code_gen forwards most of the actual construction of code for particular
% goals to other modules. The generation of code for unifications is done
% by unify_gen, for calls, higher-order calls and method calls by call_gen,
% for commits by commit_gen, for if-then-elses and negations by ite_gen,
% for switches by switch_gen and its subsidiary modules, for disjunctions
% by disj_gen, and for pragma_c_codes by pragma_c_gen. The only kind of goal
% handled directly by code_gen is the conjunction.
%
%---------------------------------------------------------------------------%
:- module code_gen.
:- interface.
:- import_module hlds_module, hlds_pred, hlds_goal, llds, code_info.
:- import_module continuation_info, globals.
:- import_module list, io.
% Translate a HLDS module to LLDS.
:- pred generate_code(module_info::in, module_info::out,
list(c_procedure)::out, io__state::di, io__state::uo) is det.
% Translate a HLDS procedure to LLDS, threading through
% the data structure that records information about layout
% structures and the counter for ensuring the uniqueness
% of cell numbers.
:- pred generate_proc_code(proc_info::in, proc_id::in, pred_id::in,
module_info::in, globals::in,
continuation_info::in, continuation_info::out, int::in, int::out,
c_procedure::out) is det.
% Translate a HLDS goal to LLDS.
:- pred code_gen__generate_goal(code_model::in, hlds_goal::in, code_tree::out,
code_info::in, code_info::out) is det.
%---------------------------------------------------------------------------%
%---------------------------------------------------------------------------%
:- implementation.
:- import_module call_gen, unify_gen, ite_gen, switch_gen, disj_gen.
:- import_module par_conj_gen, pragma_c_gen, commit_gen.
:- import_module trace, options, hlds_out.
:- import_module code_aux, middle_rec, passes_aux, llds_out.
:- import_module code_util, type_util, mode_util.
:- import_module prog_data, prog_out, instmap.
:- import_module bool, char, int, string.
:- import_module map, assoc_list, set, term, tree, std_util, require, varset.
%---------------------------------------------------------------------------%
generate_code(ModuleInfo0, ModuleInfo, Procedures) -->
% get a list of all the predicate ids
% for which we are going to generate code.
{ module_info_predids(ModuleInfo0, PredIds) },
% now generate the code for each predicate
generate_pred_list_code(ModuleInfo0, ModuleInfo, PredIds, Procedures).
% Translate a list of HLDS predicates to LLDS.
:- pred generate_pred_list_code(module_info::in, module_info::out,
list(pred_id)::in, list(c_procedure)::out,
io__state::di, io__state::uo) is det.
generate_pred_list_code(ModuleInfo, ModuleInfo, [], []) --> [].
generate_pred_list_code(ModuleInfo0, ModuleInfo, [PredId | PredIds],
Predicates) -->
{ module_info_preds(ModuleInfo0, PredInfos) },
% get the pred_info structure for this predicate
{ map__lookup(PredInfos, PredId, PredInfo) },
% extract a list of all the procedure ids for this
% predicate and generate code for them
{ pred_info_non_imported_procids(PredInfo, ProcIds) },
( { ProcIds = [] } ->
{ Predicates0 = [] },
{ ModuleInfo1 = ModuleInfo0 }
;
generate_pred_code(ModuleInfo0, ModuleInfo1, PredId,
PredInfo, ProcIds, Predicates0)
),
{ list__append(Predicates0, Predicates1, Predicates) },
% and generate the code for the rest of the predicates
generate_pred_list_code(ModuleInfo1, ModuleInfo, PredIds, Predicates1).
% Translate a HLDS predicate to LLDS.
:- pred generate_pred_code(module_info::in, module_info::out,
pred_id::in, pred_info::in, list(proc_id)::in, list(c_procedure)::out,
io__state::di, io__state::uo) is det.
generate_pred_code(ModuleInfo0, ModuleInfo, PredId, PredInfo, ProcIds, Code) -->
globals__io_lookup_bool_option(very_verbose, VeryVerbose),
( { VeryVerbose = yes } ->
io__write_string("% Generating code for "),
hlds_out__write_pred_id(ModuleInfo0, PredId),
io__write_string("\n"),
globals__io_lookup_bool_option(statistics, Statistics),
maybe_report_stats(Statistics)
;
[]
),
{ module_info_get_continuation_info(ModuleInfo0, ContInfo0) },
{ module_info_get_cell_count(ModuleInfo0, CellCount0) },
globals__io_get_globals(Globals),
{ generate_proc_list_code(ProcIds, PredId, PredInfo, ModuleInfo0,
Globals, ContInfo0, ContInfo, CellCount0, CellCount,
[], Code) },
{ module_info_set_cell_count(ModuleInfo0, CellCount, ModuleInfo1) },
{ module_info_set_continuation_info(ModuleInfo1, ContInfo,
ModuleInfo) }.
% Translate all the procedures of a HLDS predicate to LLDS.
:- pred generate_proc_list_code(list(proc_id)::in, pred_id::in, pred_info::in,
module_info::in, globals::in,
continuation_info::in, continuation_info::out, int::in, int::out,
list(c_procedure)::in, list(c_procedure)::out) is det.
generate_proc_list_code([], _PredId, _PredInfo, _ModuleInfo, _Globals,
ContInfo, ContInfo, CellCount, CellCount, Procs, Procs).
generate_proc_list_code([ProcId | ProcIds], PredId, PredInfo, ModuleInfo0,
Globals, ContInfo0, ContInfo, CellCount0, CellCount,
Procs0, Procs) :-
pred_info_procedures(PredInfo, ProcInfos),
map__lookup(ProcInfos, ProcId, ProcInfo),
generate_proc_code(ProcInfo, ProcId, PredId, ModuleInfo0, Globals,
ContInfo0, ContInfo1, CellCount0, CellCount1, Proc),
generate_proc_list_code(ProcIds, PredId, PredInfo, ModuleInfo0,
Globals, ContInfo1, ContInfo, CellCount1, CellCount,
[Proc | Procs0], Procs).
%---------------------------------------------------------------------------%
% Values of this type hold information about stack frames that is
% generated when generating prologs and is used in generating epilogs
% and when massaging the code generated for the procedure.
:- type frame_info
---> frame(
int, % Number of slots in frame.
maybe(int), % Slot number of succip if succip is
% present in a general slot.
bool % Is this the frame of a model_non
% proc defined via pragma C code?
).
%---------------------------------------------------------------------------%
generate_proc_code(ProcInfo, ProcId, PredId, ModuleInfo, Globals,
ContInfo0, ContInfo, CellCount0, CellCount, Proc) :-
proc_info_interface_determinism(ProcInfo, Detism),
proc_info_interface_code_model(ProcInfo, CodeModel),
proc_info_goal(ProcInfo, Goal),
proc_info_varset(ProcInfo, VarSet),
proc_info_liveness_info(ProcInfo, Liveness),
proc_info_stack_slots(ProcInfo, StackSlots),
proc_info_get_initial_instmap(ProcInfo, ModuleInfo, InitialInst),
Goal = _ - GoalInfo,
goal_info_get_follow_vars(GoalInfo, MaybeFollowVars),
(
MaybeFollowVars = yes(FollowVars)
;
MaybeFollowVars = no,
map__init(FollowVars)
),
globals__lookup_bool_option(Globals, basic_stack_layout,
BasicStackLayout),
( BasicStackLayout = yes ->
SaveSuccip = yes
;
SaveSuccip = no
),
% Initialise the code_info structure. Generate_category_code
% below will use the returned OutsideResumePoint as the
% entry to the code that handles the failure of the procedure,
% if such code is needed. It is never needed for model_det
% procedures, always needed for model_semi procedures, and
% needed for model_non procedures only if we are doing
% execution tracing.
code_info__init(VarSet, Liveness, StackSlots, SaveSuccip, Globals,
PredId, ProcId, ProcInfo, InitialInst, FollowVars,
ModuleInfo, CellCount0, OutsideResumePoint, CodeInfo0),
% Generate code for the procedure.
generate_category_code(CodeModel, Goal, OutsideResumePoint,
CodeTree, MaybeTraceCallLabel, FrameInfo, CodeInfo0, CodeInfo),
code_info__get_cell_count(CellCount, CodeInfo, _),
% Turn the code tree into a list.
tree__flatten(CodeTree, FragmentList),
% Now the code is a list of code fragments (== list(instr)),
% so we need to do a level of unwinding to get a flat list.
list__condense(FragmentList, Instructions0),
FrameInfo = frame(TotalSlots, MaybeSuccipSlot, _),
(
MaybeSuccipSlot = yes(SuccipSlot)
->
% The set of recorded live values at calls (for value
% numbering) and returns (for accurate gc and execution
% tracing) do not yet record the stack slot holding the
% succip, so add it to those sets.
code_gen__add_saved_succip(Instructions0,
SuccipSlot, Instructions)
;
Instructions = Instructions0
),
( BasicStackLayout = yes ->
% Create the procedure layout structure.
code_info__get_layout_info(LayoutInfo, CodeInfo, _),
code_util__make_local_entry_label(ModuleInfo, PredId, ProcId,
no, EntryLabel),
continuation_info__add_proc_info(proc(PredId, ProcId),
EntryLabel, TotalSlots, Detism, MaybeSuccipSlot,
MaybeTraceCallLabel, LayoutInfo, ContInfo0, ContInfo)
;
ContInfo = ContInfo0
),
predicate_name(ModuleInfo, PredId, Name),
predicate_arity(ModuleInfo, PredId, Arity),
% Construct a c_procedure structure with all the information.
Proc = c_procedure(Name, Arity, proc(PredId, ProcId), Instructions).
%---------------------------------------------------------------------------%
%---------------------------------------------------------------------------%
% Generate_category_code generates code for an entire procedure.
% Its algorithm has three or four main stages:
%
% - generate code for the body goal
% - generate code for the procedure entry
% - generate code for the procedure exit
% - generate code for the procedure fail (if needed)
%
% The first three tasks are forwarded to other procedures.
% The fourth task, if needed, is done by generate_category_code.
%
% The only caller of generate_category_code, generate_proc_code,
% has set up the code generator state to reflect what the machine
% state will be on entry to the procedure. Ensuring that the
% machine state at exit will conform to the expectation
% of the caller is the job of code_gen__generate_exit.
%
% The reason why we generate the entry code after the body is that
% information such as the total number of stack slots needed,
% which is needed in the procedure entry prologue, cannot be
% conveniently obtained before generating the body, since the
% code generator may allocate temporary variables to hold values
% such as saved heap and trail pointers.
%
% Code_gen__generate_entry cannot depend on the code generator
% state, since when it is invoked this state is not appropriate
% for the procedure entry. Nor can it change the code generator state,
% since that would confuse code_gen__generate_exit.
%
% Generating CALL trace events is done by generate_category_code,
% since only on entry to generate_category_code is the code generator
% state set up right. Generating EXIT trace events is done by
% code_gen__generate_exit. Generating FAIL trace events is done
% by generate_category_code, since this requires modifying how
% we generate code for the body of the procedure (failures must
% now branch to a different place). Since FAIL trace events are
% part of the failure continuation, generate_category_code takes
% care of the failure continuation as well. (Model_det procedures
% of course have no failure continuation. Model_non procedures have
% a failure continuation, but in the absence of tracing this
% continuation needs no code. Only model_semi procedures need code
% for the failure continuation at all times.)
:- pred generate_category_code(code_model::in, hlds_goal::in,
resume_point_info::in, code_tree::out, maybe(label)::out,
frame_info::out, code_info::in, code_info::out) is det.
generate_category_code(model_det, Goal, ResumePoint, Code,
MaybeTraceCallLabel, FrameInfo) -->
% generate the code for the body of the clause
(
code_info__get_globals(Globals),
{ globals__lookup_bool_option(Globals, middle_rec, yes) },
middle_rec__match_and_generate(Goal, MiddleRecCode)
->
{ Code = MiddleRecCode },
{ MaybeTraceCallLabel = no },
{ FrameInfo = frame(0, no, no) }
;
code_info__get_maybe_trace_info(MaybeTraceInfo),
( { MaybeTraceInfo = yes(TraceInfo) } ->
trace__generate_external_event_code(call, TraceInfo,
TraceCallLabel, _TypeInfos, TraceCallCode),
{ MaybeTraceCallLabel = yes(TraceCallLabel) }
;
{ TraceCallCode = empty },
{ MaybeTraceCallLabel = no }
),
code_gen__generate_goal(model_det, Goal, BodyCode),
code_gen__generate_entry(model_det, Goal, ResumePoint,
FrameInfo, EntryCode),
code_gen__generate_exit(model_det, FrameInfo, _, ExitCode),
{ Code =
tree(EntryCode,
tree(TraceCallCode,
tree(BodyCode,
ExitCode)))
}
).
generate_category_code(model_semi, Goal, ResumePoint, Code,
MaybeTraceCallLabel, FrameInfo) -->
{ set__singleton_set(FailureLiveRegs, reg(r, 1)) },
{ FailCode = node([
assign(reg(r, 1), const(false)) - "Fail",
livevals(FailureLiveRegs) - "",
goto(succip) - "Return from procedure call"
]) },
code_info__get_maybe_trace_info(MaybeTraceInfo),
( { MaybeTraceInfo = yes(TraceInfo) } ->
trace__generate_external_event_code(call, TraceInfo,
TraceCallLabel, _TypeInfos, TraceCallCode),
{ MaybeTraceCallLabel = yes(TraceCallLabel) },
code_gen__generate_goal(model_semi, Goal, BodyCode),
code_gen__generate_entry(model_semi, Goal, ResumePoint,
FrameInfo, EntryCode),
code_gen__generate_exit(model_semi, FrameInfo,
RestoreDeallocCode, ExitCode),
code_info__generate_resume_point(ResumePoint, ResumeCode),
{ code_info__resume_point_vars(ResumePoint, ResumeVarList) },
{ set__list_to_set(ResumeVarList, ResumeVars) },
code_info__set_forward_live_vars(ResumeVars),
trace__generate_external_event_code(fail, TraceInfo, _, _,
TraceFailCode),
{ Code =
tree(EntryCode,
tree(TraceCallCode,
tree(BodyCode,
tree(ExitCode,
tree(ResumeCode,
tree(TraceFailCode,
tree(RestoreDeallocCode,
FailCode)))))))
}
;
{ MaybeTraceCallLabel = no },
code_gen__generate_goal(model_semi, Goal, BodyCode),
code_gen__generate_entry(model_semi, Goal, ResumePoint,
FrameInfo, EntryCode),
code_gen__generate_exit(model_semi, FrameInfo,
RestoreDeallocCode, ExitCode),
code_info__generate_resume_point(ResumePoint, ResumeCode),
{ Code =
tree(EntryCode,
tree(BodyCode,
tree(ExitCode,
tree(ResumeCode,
tree(RestoreDeallocCode,
FailCode)))))
}
).
generate_category_code(model_non, Goal, ResumePoint, Code,
MaybeTraceCallLabel, FrameInfo) -->
code_info__get_maybe_trace_info(MaybeTraceInfo),
( { MaybeTraceInfo = yes(TraceInfo) } ->
trace__generate_external_event_code(call, TraceInfo,
TraceCallLabel, _TypeInfos, TraceCallCode),
{ MaybeTraceCallLabel = yes(TraceCallLabel) },
code_gen__generate_goal(model_non, Goal, BodyCode),
code_gen__generate_entry(model_non, Goal, ResumePoint,
FrameInfo, EntryCode),
code_gen__generate_exit(model_non, FrameInfo, _, ExitCode),
code_info__generate_resume_point(ResumePoint, ResumeCode),
{ code_info__resume_point_vars(ResumePoint, ResumeVarList) },
{ set__list_to_set(ResumeVarList, ResumeVars) },
code_info__set_forward_live_vars(ResumeVars),
trace__generate_external_event_code(fail, TraceInfo, _, _,
TraceFailCode),
{ FailCode = node([
goto(do_fail) - "fail after fail trace port"
]) },
{ Code =
tree(EntryCode,
tree(TraceCallCode,
tree(BodyCode,
tree(ExitCode,
tree(ResumeCode,
tree(TraceFailCode,
FailCode))))))
}
;
{ MaybeTraceCallLabel = no },
code_gen__generate_goal(model_non, Goal, BodyCode),
code_gen__generate_entry(model_non, Goal, ResumePoint,
FrameInfo, EntryCode),
code_gen__generate_exit(model_non, FrameInfo, _, ExitCode),
{ Code =
tree(EntryCode,
tree(BodyCode,
ExitCode))
}
).
%---------------------------------------------------------------------------%
% Generate the prologue for a procedure.
%
% The prologue will contain
%
% a comment to mark prologue start
% a comment explaining the stack layout
% the procedure entry label
% code to allocate a stack frame
% code to fill in some special slots in the stack frame
% a comment to mark prologue end
%
% At the moment the only special slots are the succip slot, and
% the slots holding the call number and call depth for tracing.
%
% Not all frames will have all these components. For example, the code
% to allocate a stack frame will be missing if the procedure doesn't
% need a stack frame, and if the procedure is nondet, then the code
% to fill in the succip slot is subsumed by the mkframe.
:- pred code_gen__generate_entry(code_model::in, hlds_goal::in,
resume_point_info::in, frame_info::out, code_tree::out,
code_info::in, code_info::out) is det.
code_gen__generate_entry(CodeModel, Goal, OutsideResumePoint,
FrameInfo, EntryCode) -->
code_info__get_stack_slots(StackSlots),
code_info__get_varset(VarSet),
{ code_aux__explain_stack_slots(StackSlots, VarSet, SlotsComment) },
{ StartComment = node([
comment("Start of procedure prologue") - "",
comment(SlotsComment) - ""
]) },
code_info__get_total_stackslot_count(MainSlots),
code_info__get_pred_id(PredId),
code_info__get_proc_id(ProcId),
code_info__get_module_info(ModuleInfo),
{ code_util__make_local_entry_label(ModuleInfo, PredId, ProcId, no,
Entry) },
{ LabelCode = node([
label(Entry) - "Procedure entry point"
]) },
code_info__get_succip_used(Used),
(
% Do we need to save the succip across calls?
{ Used = yes },
% Do we need to use a general slot for storing succip?
{ CodeModel \= model_non }
->
{ SuccipSlot is MainSlots + 1 },
{ SaveSuccipCode = node([
assign(stackvar(SuccipSlot), lval(succip)) -
"Save the success ip"
]) },
{ TotalSlots = SuccipSlot },
{ MaybeSuccipSlot = yes(SuccipSlot) }
;
{ SaveSuccipCode = empty },
{ TotalSlots = MainSlots },
{ MaybeSuccipSlot = no }
),
code_info__get_maybe_trace_info(MaybeTraceInfo),
( { MaybeTraceInfo = yes(TraceInfo) } ->
{ trace__generate_slot_fill_code(TraceInfo, TraceFillCode) }
;
{ TraceFillCode = empty }
),
{ predicate_module(ModuleInfo, PredId, ModuleName) },
{ predicate_name(ModuleInfo, PredId, PredName) },
{ predicate_arity(ModuleInfo, PredId, Arity) },
{ prog_out__sym_name_to_string(ModuleName, ModuleNameString) },
{ string__int_to_string(Arity, ArityStr) },
{ string__append_list([ModuleNameString, ":", PredName, "/", ArityStr],
PushMsg) },
(
{ CodeModel = model_non }
->
{ code_info__resume_point_stack_addr(OutsideResumePoint,
OutsideResumeAddress) },
(
{ Goal = pragma_c_code(_,_,_,_,_,_, PragmaCode) - _},
{ PragmaCode = nondet(Fields, FieldsContext,
_,_,_,_,_,_,_) }
->
{ pragma_c_gen__struct_name(ModuleName, PredName,
Arity, ProcId, StructName) },
{ Struct = pragma_c_struct(StructName,
Fields, FieldsContext) },
{ string__format("#define\tMR_ORDINARY_SLOTS\t%d\n",
[i(TotalSlots)], DefineStr) },
{ DefineComponents = [pragma_c_raw_code(DefineStr)] },
{ NondetFrameInfo = ordinary_frame(PushMsg, TotalSlots,
yes(Struct)) },
{ AllocCode = node([
mkframe(NondetFrameInfo, OutsideResumeAddress)
- "Allocate stack frame",
pragma_c([], DefineComponents,
will_not_call_mercury, no, no)
- ""
]) },
{ NondetPragma = yes }
;
{ NondetFrameInfo = ordinary_frame(PushMsg, TotalSlots,
no) },
{ AllocCode = node([
mkframe(NondetFrameInfo, OutsideResumeAddress)
- "Allocate stack frame"
]) },
{ NondetPragma = no }
)
;
{ TotalSlots > 0 }
->
{ AllocCode = node([
incr_sp(TotalSlots, PushMsg) -
"Allocate stack frame"
]) },
{ NondetPragma = no }
;
{ AllocCode = empty },
{ NondetPragma = no }
),
{ FrameInfo = frame(TotalSlots, MaybeSuccipSlot, NondetPragma) },
{ EndComment = node([
comment("End of procedure prologue") - ""
]) },
{ EntryCode =
tree(StartComment,
tree(LabelCode,
tree(AllocCode,
tree(SaveSuccipCode,
tree(TraceFillCode,
EndComment)))))
}.
%---------------------------------------------------------------------------%
% Generate the success epilogue for a procedure.
%
% The success epilogue will contain
%
% a comment to mark epilogue start
% code to place the output arguments where their caller expects
% code to restore registers from some special slots
% code to deallocate the stack frame
% code to set r1 to TRUE (for semidet procedures only)
% a jump back to the caller, including livevals information
% a comment to mark epilogue end
%
% The parts of this that restore registers and deallocate the stack
% frame are also part of the failure epilog, which is handled by
% our caller; this is why we return RestoreDeallocCode.
%
% At the moment the only special slots are the succip slot, and
% the slots holding the call number and call depth for tracing.
%
% Not all frames will have all these components. For example, for
% nondet procedures we don't deallocate the stack frame before
% success.
%
% Epilogues for procedures defined by nondet pragma C codes do not
% follow the rules above. For such procedures, the normal functions
% of the epilogue are handled when traversing the pragma C code goal;
% we need only #undef a macro defined by the procedure prologue.
:- pred code_gen__generate_exit(code_model::in, frame_info::in,
code_tree::out, code_tree::out, code_info::in, code_info::out) is det.
code_gen__generate_exit(CodeModel, FrameInfo, RestoreDeallocCode, ExitCode) -->
{ StartComment = node([
comment("Start of procedure epilogue") - ""
]) },
{ EndComment = node([
comment("End of procedure epilogue") - ""
]) },
{ FrameInfo = frame(TotalSlots, MaybeSuccipSlot, NondetPragma) },
( { NondetPragma = yes } ->
{ UndefStr = "#undef\tMR_ORDINARY_SLOTS\n" },
{ UndefComponents = [pragma_c_raw_code(UndefStr)] },
{ UndefCode = node([
pragma_c([], UndefComponents,
will_not_call_mercury, no, no)
- ""
]) },
{ RestoreDeallocCode = empty }, % always empty for nondet code
{ ExitCode =
tree(StartComment,
tree(UndefCode,
EndComment))
}
;
code_info__get_instmap(Instmap),
code_info__get_arginfo(ArgModes),
code_info__get_headvars(HeadVars),
{ assoc_list__from_corresponding_lists(HeadVars, ArgModes,
Args)},
(
{ instmap__is_unreachable(Instmap) }
->
{ FlushCode = empty }
;
code_info__setup_call(Args, callee, FlushCode)
),
(
{ MaybeSuccipSlot = yes(SuccipSlot) }
->
{ RestoreSuccipCode = node([
assign(succip, lval(stackvar(SuccipSlot))) -
"restore the success ip"
]) }
;
{ RestoreSuccipCode = empty }
),
(
{ TotalSlots = 0 ; CodeModel = model_non }
->
{ DeallocCode = empty }
;
{ DeallocCode = node([
decr_sp(TotalSlots) - "Deallocate stack frame"
]) }
),
{ RestoreDeallocCode = tree(RestoreSuccipCode, DeallocCode ) },
code_info__get_maybe_trace_info(MaybeTraceInfo),
( { MaybeTraceInfo = yes(TraceInfo) } ->
trace__generate_external_event_code(exit, TraceInfo,
_, TypeInfoDatas, TraceExitCode),
{ assoc_list__values(TypeInfoDatas, TypeInfoLvals) }
;
{ TraceExitCode = empty },
{ TypeInfoLvals = [] }
),
% Find out which locations should be mentioned
% in the success path livevals(...) annotation,
% so that value numbering doesn't optimize them away.
{ code_gen__select_args_with_mode(Args, top_out, _OutVars,
OutLvals) },
{ list__append(TypeInfoLvals, OutLvals, LiveArgLvals) },
{ set__list_to_set(LiveArgLvals, LiveArgs) },
(
{ CodeModel = model_det },
{ SuccessCode = node([
livevals(LiveArgs) - "",
goto(succip) - "Return from procedure call"
]) },
{ AllSuccessCode =
tree(TraceExitCode,
tree(RestoreDeallocCode,
SuccessCode))
}
;
{ CodeModel = model_semi },
{ set__insert(LiveArgs, reg(r, 1), SuccessLiveRegs) },
{ SuccessCode = node([
assign(reg(r, 1), const(true)) - "Succeed",
livevals(SuccessLiveRegs) - "",
goto(succip) - "Return from procedure call"
]) },
{ AllSuccessCode =
tree(TraceExitCode,
tree(RestoreDeallocCode,
SuccessCode))
}
;
{ CodeModel = model_non },
{ SuccessCode = node([
livevals(LiveArgs) - "",
goto(do_succeed(no))
- "Return from procedure call"
]) },
{ AllSuccessCode =
tree(TraceExitCode,
SuccessCode)
}
),
{ ExitCode =
tree(StartComment,
tree(FlushCode,
tree(AllSuccessCode,
EndComment)))
}
).
%---------------------------------------------------------------------------%
% Generate a goal. This predicate arranges for the necessary updates of
% the generic data structures before and after the actual code generation,
% which is delegated to goal-specific predicates.
code_gen__generate_goal(ContextModel, Goal - GoalInfo, Code) -->
% Make any changes to liveness before Goal
{ goal_is_atomic(Goal) ->
IsAtomic = yes
;
IsAtomic = no
},
code_info__pre_goal_update(GoalInfo, IsAtomic),
code_info__get_instmap(Instmap),
(
{ instmap__is_reachable(Instmap) }
->
{ goal_info_get_code_model(GoalInfo, CodeModel) },
% sanity check: code of some code models
% should occur only in limited contexts
{
CodeModel = model_det
;
CodeModel = model_semi,
( ContextModel \= model_det ->
true
;
error("semidet model in det context")
)
;
CodeModel = model_non,
( ContextModel = model_non ->
true
;
error("nondet model in det/semidet context")
)
},
code_gen__generate_goal_2(Goal, GoalInfo, CodeModel, Code),
% Make live any variables which subsequent goals
% will expect to be live, but were not generated
code_info__set_instmap(Instmap),
code_info__post_goal_update(GoalInfo)
;
{ Code = empty }
),
!.
%---------------------------------------------------------------------------%
:- pred code_gen__generate_goal_2(hlds_goal_expr::in, hlds_goal_info::in,
code_model::in, code_tree::out, code_info::in, code_info::out) is det.
code_gen__generate_goal_2(unify(_, _, _, Uni, _), _, CodeModel, Code) -->
unify_gen__generate_unification(CodeModel, Uni, Code).
code_gen__generate_goal_2(conj(Goals), _GoalInfo, CodeModel, Code) -->
code_gen__generate_goals(Goals, CodeModel, Code).
code_gen__generate_goal_2(par_conj(Goals, _SM), GoalInfo, CodeModel, Code) -->
par_conj_gen__generate_par_conj(Goals, GoalInfo, CodeModel, Code).
code_gen__generate_goal_2(disj(Goals, StoreMap), _, CodeModel, Code) -->
disj_gen__generate_disj(CodeModel, Goals, StoreMap, Code).
code_gen__generate_goal_2(not(Goal), _GoalInfo, CodeModel, Code) -->
ite_gen__generate_negation(CodeModel, Goal, Code).
code_gen__generate_goal_2(if_then_else(_Vars, Cond, Then, Else, StoreMap),
_GoalInfo, CodeModel, Code) -->
ite_gen__generate_ite(CodeModel, Cond, Then, Else, StoreMap, Code).
code_gen__generate_goal_2(switch(Var, CanFail, CaseList, StoreMap),
GoalInfo, CodeModel, Code) -->
switch_gen__generate_switch(CodeModel, Var, CanFail, CaseList,
StoreMap, GoalInfo, Code).
code_gen__generate_goal_2(some(_Vars, Goal), _GoalInfo, CodeModel, Code) -->
commit_gen__generate_commit(CodeModel, Goal, Code).
code_gen__generate_goal_2(higher_order_call(PredVar, Args, Types,
Modes, Det, _PredOrFunc), GoalInfo, CodeModel, Code) -->
call_gen__generate_higher_order_call(CodeModel, PredVar, Args,
Types, Modes, Det, GoalInfo, Code).
code_gen__generate_goal_2(class_method_call(TCVar, Num, Args, Types,
Modes, Det), GoalInfo, CodeModel, Code) -->
call_gen__generate_class_method_call(CodeModel, TCVar, Num, Args,
Types, Modes, Det, GoalInfo, Code).
code_gen__generate_goal_2(call(PredId, ProcId, Args, BuiltinState, _, _),
GoalInfo, CodeModel, Code) -->
(
{ BuiltinState = not_builtin }
->
call_gen__generate_call(CodeModel, PredId, ProcId, Args,
GoalInfo, Code)
;
call_gen__generate_builtin(CodeModel, PredId, ProcId, Args,
Code)
).
code_gen__generate_goal_2(pragma_c_code(MayCallMercury, PredId, ProcId,
Args, ArgNames, OrigArgTypes, PragmaImpl),
GoalInfo, CodeModel, Code) -->
pragma_c_gen__generate_pragma_c_code(CodeModel, MayCallMercury,
PredId, ProcId, Args, ArgNames, OrigArgTypes, GoalInfo,
PragmaImpl, Code).
%---------------------------------------------------------------------------%
% Generate a conjoined series of goals.
% Note of course, that with a conjunction, state information
% flows directly from one conjunct to the next.
:- pred code_gen__generate_goals(hlds_goals::in, code_model::in,
code_tree::out, code_info::in, code_info::out) is det.
code_gen__generate_goals([], _, empty) --> [].
code_gen__generate_goals([Goal | Goals], CodeModel, Instr) -->
code_gen__generate_goal(CodeModel, Goal, Instr1),
code_info__get_instmap(Instmap),
(
{ instmap__is_unreachable(Instmap) }
->
{ Instr = Instr1 }
;
code_gen__generate_goals(Goals, CodeModel, Instr2),
{ Instr = tree(Instr1, Instr2) }
).
%---------------------------------------------------------------------------%
:- pred code_gen__select_args_with_mode(assoc_list(var, arg_info)::in,
arg_mode::in, list(var)::out, list(lval)::out) is det.
code_gen__select_args_with_mode([], _, [], []).
code_gen__select_args_with_mode([Var - ArgInfo | Args], DesiredMode, Vs, Ls) :-
code_gen__select_args_with_mode(Args, DesiredMode, Vs0, Ls0),
ArgInfo = arg_info(Loc, Mode),
(
Mode = DesiredMode
->
code_util__arg_loc_to_register(Loc, Reg),
Vs = [Var | Vs0],
Ls = [Reg | Ls0]
;
Vs = Vs0,
Ls = Ls0
).
%---------------------------------------------------------------------------%
% Add the succip to the livevals before and after calls.
% Traverses the list of instructions looking for livevals and calls,
% adding succip in the stackvar number given as an argument.
:- pred code_gen__add_saved_succip(list(instruction)::in, int::in,
list(instruction)::out) is det.
code_gen__add_saved_succip([], _StackLoc, []).
code_gen__add_saved_succip([Instrn0 - Comment | Instrns0 ], StackLoc,
[Instrn - Comment | Instrns]) :-
(
Instrn0 = livevals(LiveVals0),
Instrns0 \= [goto(succip) - _ | _]
% XXX We should also test for tailcalls
% once we start generating them directly.
->
set__insert(LiveVals0, stackvar(StackLoc), LiveVals1),
Instrn = livevals(LiveVals1)
;
Instrn0 = call(Target, ReturnLabel, LiveVals0, CM)
->
Instrn = call(Target, ReturnLabel,
[live_lvalue(stackvar(StackLoc), succip, "", []) |
LiveVals0], CM)
;
Instrn = Instrn0
),
code_gen__add_saved_succip(Instrns0, StackLoc, Instrns).
%---------------------------------------------------------------------------%
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