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frameopt.m
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frameopt.m
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%-----------------------------------------------------------------------------%
% vim: ft=mercury ts=4 sw=4 et
%-----------------------------------------------------------------------------%
% Copyright (C) 1994-2001,2003-2012 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.
%-----------------------------------------------------------------------------%
%
% File: frameopt.m.
% Main author: zs.
%
% This module performs two kinds of transformation to optimize code that
% manipulates detstack frames.
%
% The first and more common transformation transforms code such as
%
% proc_entry:
% incr_sp(N)
% stackvar(N) = succip
% if (cond) goto L1
% ...
% L1: finalization
% succip = stackvar(N)
% decr_sp(N)
% proceed
%
% into
%
% proc_entry:
% if (cond) goto L1
% incr_sp(N)
% stackvar(N) = succip
% ...
% finalization
% succip = stackvar(N)
% decr_sp(N)
% proceed
% L1: finalization
% proceed
%
% The advantage is that we don't set up the stack frame unless we need it.
%
% The actual optimization is more complex than this, because we want to delay
% the construction of the stack frame across more than one jump, if this is
% possible.
%
% The second transformation transforms code such as
%
% proc_entry:
% incr_sp(N)
% stackvar(N) = succip
% ...
% finalization
% succip = stackvar(N)
% decr_sp(N)
% goto proc_entry
%
% into
%
% proc_entry:
% incr_sp(N)
% stackvar(N) = succip
% L1:
% ...
% succip = stackvar(N)
% finalization
% goto L1
%
% The advantage is that we don't destroy the stack frame just to set it up
% again. The restore of succip can be omitted if the procedure makes no calls,
% since in that case succip must still contain the value it had when this
% procedure was called.
%
% Since the second transformation is a bigger win, we prefer to use it
% whenever both transformations are possible.
%
% For predicates that live on the nondet stack, we attempt to perform
% only the second transformation.
%
% NOTE: This module cannot handle code sequences of the form
%
% label1:
% label2:
%
% Jump optimization converts any gotos to label1 to gotos to label2, making
% label1 unused, and label optimization removes unused labels. (This works
% for any number of labels in a sequence, not just two.) Therefore the
% handle_options module turns on the jump and label optimizations whenever
% frame optimization is turned on.
%
%-----------------------------------------------------------------------------%
:- module ll_backend.frameopt.
:- interface.
:- import_module ll_backend.llds.
:- import_module mdbcomp.
:- import_module mdbcomp.prim_data.
:- import_module bool.
:- import_module counter.
:- import_module list.
:- import_module set_tree234.
%-----------------------------------------------------------------------------%
% frameopt_main_det_stack(ProcLabel, !LabelCounter, !Instrs, AddComments,
% AnyChange):
%
% Attempt to update !Instrs using the one of the transformations
% described above for procedures that live on the det stack.
%
% ProcLabel should be the ProcLabel of the procedure whose body !.Instrs
% implements, and !.LabelCounter that procedure's label counter.
% If frameopt_main allocates any labels, !:LabelCounter will reflect this.
%
% AnyChange says whether we performed any modifications.
% If yes, then we also introduced some extra labels that should be
% deleted and probably some jumps that could be profitably be
% short-circuited.
%
:- pred frameopt_main_det_stack(proc_label::in, counter::in, counter::out,
list(instruction)::in, list(instruction)::out, bool::in, bool::out)
is det.
% frameopt_main_nondet_stack(ProcLabel, !LabelCounter, !Instrs,
% AddComments, AnyChange):
%
% The equivalent of frameopt_main_det_stack for procedures that live on
% the nondet stack, but attempting only the transformation that delays
% the creation of stack frames.
%
:- pred frameopt_main_nondet_stack(proc_label::in, counter::in, counter::out,
list(instruction)::in, list(instruction)::out, bool::in, bool::out)
is det.
% frameopt_keep_nondet_frame(ProcLabel, LayoutLabels,
% !LabelCounter, !Instrs, AnyChange):
%
% The equivalent of frameopt_main_det_stack for procedures that live on
% the nondet stack, but attempting only the transformation that keeps
% existing stack frames at tail calls. This should be called before
% other LLDS optimizations on the procedure body.
%
% LayoutLabels should be the set of labels in the procedure with layout
% structures, while MayAlterRtti should say whether we are allowed to
% perform optimizations that may interfere with RTTI.
%
:- pred frameopt_keep_nondet_frame(proc_label::in, set_tree234(label)::in,
counter::in, counter::out, list(instruction)::in, list(instruction)::out,
bool::out) is det.
%-----------------------------------------------------------------------------%
%-----------------------------------------------------------------------------%
:- implementation.
:- import_module ll_backend.opt_debug.
:- import_module ll_backend.opt_util.
:- import_module parse_tree.
:- import_module parse_tree.prog_data_foreign.
:- import_module assoc_list.
:- import_module int.
:- import_module map.
:- import_module maybe.
:- import_module pair.
:- import_module queue.
:- import_module require.
:- import_module set.
:- import_module string.
%-----------------------------------------------------------------------------%
frameopt_main_det_stack(ProcLabel, !C, Instrs0, Instrs, AddComments, Mod) :-
opt_util.get_prologue(Instrs0, LabelInstr, Comments0, Instrs1),
( if detect_det_entry(Instrs1, _, _, EntryInfo) then
some [!BlockMap] (
map.init(!:BlockMap),
divide_into_basic_blocks([LabelInstr | Instrs1], ProcLabel,
BasicInstrs, !C),
build_frame_block_map(BasicInstrs, EntryInfo, LabelSeq0, no, no,
ProcLabel, !BlockMap, map.init, PredMap, !C,
map.init, PreExitDummyLabelMap),
analyze_block_map(LabelSeq0, PreExitDummyLabelMap, !BlockMap,
KeepFrame),
(
KeepFrame = yes(FirstLabel - SecondLabel),
CanClobberSuccip = can_clobber_succip(LabelSeq0, !.BlockMap),
keep_frame_transform(LabelSeq0, FirstLabel, SecondLabel,
CanClobberSuccip, !BlockMap),
LabelSeq = LabelSeq0,
NewComment = llds_instr(comment("keeping stack frame"), ""),
Comments = Comments0 ++ [NewComment],
flatten_block_seq(LabelSeq, !.BlockMap, BodyInstrs),
Instrs = Comments ++ BodyInstrs,
Mod = yes
;
KeepFrame = no,
( if can_delay_frame(LabelSeq0, !.BlockMap) then
delay_frame_transform(LabelSeq0, LabelSeq, EntryInfo,
ProcLabel, PredMap, !C, !BlockMap, AddComments,
TransformComments, DescComments, CanTransform),
(
CanTransform = can_transform,
Comments = Comments0 ++ TransformComments
++ DescComments,
flatten_block_seq(LabelSeq, !.BlockMap, BodyInstrs),
Instrs = Comments ++ BodyInstrs,
Mod = yes
;
CanTransform = cannot_transform,
maybe_add_comments(AddComments, DescComments,
Instrs0, Instrs, Mod)
)
else
Instrs = Instrs0,
Mod = no
)
)
)
else
Instrs = Instrs0,
Mod = no
).
frameopt_main_nondet_stack(ProcLabel, !C, Instrs0, Instrs, AddComments, Mod) :-
opt_util.get_prologue(Instrs0, LabelInstr, Comments0, Instrs1),
( if detect_nondet_entry(Instrs1, _, _, EntryInfo) then
some [!BlockMap] (
map.init(!:BlockMap),
divide_into_basic_blocks([LabelInstr | Instrs1], ProcLabel,
BasicInstrs, !C),
build_frame_block_map(BasicInstrs, EntryInfo, LabelSeq0, no, no,
ProcLabel, !BlockMap, map.init, PredMap, !C,
map.init, PreExitDummyLabelMap),
analyze_block_map(LabelSeq0, PreExitDummyLabelMap, !BlockMap,
_KeepFrame),
( if can_delay_frame(LabelSeq0, !.BlockMap) then
delay_frame_transform(LabelSeq0, LabelSeq, EntryInfo,
ProcLabel, PredMap, !C, !BlockMap, AddComments,
TransformComments, DescComments, CanTransform),
(
CanTransform = can_transform,
Comments = Comments0 ++ TransformComments ++ DescComments,
flatten_block_seq(LabelSeq, !.BlockMap, BodyInstrs),
Instrs = Comments ++ BodyInstrs,
Mod = yes
;
CanTransform = cannot_transform,
maybe_add_comments(AddComments, DescComments,
Instrs0, Instrs, Mod)
)
else
Instrs = Instrs0,
Mod = no
)
)
else
Instrs = Instrs0,
Mod = no
).
:- pred maybe_add_comments(bool::in, list(instruction)::in,
list(instruction)::in, list(instruction)::out, bool::out) is det.
maybe_add_comments(Comments, DescComments, Instrs0, Instrs, Mod) :-
(
Comments = no,
Instrs = Instrs0,
Mod = no
;
Comments = yes,
Instrs =
[llds_instr(comment("could not delay frame creation"), "")]
++ DescComments ++ Instrs0,
Mod = yes
).
%-----------------------------------------------------------------------------%
frameopt_keep_nondet_frame(ProcLabel, LayoutLabels, !C, Instrs0, Instrs,
Mod) :-
opt_util.get_prologue(Instrs0, LabelInstr, Comments0, Instrs1),
( if
nondetstack_setup(Instrs1, FrameInfo, Redoip, MkframeInstr, Remain),
MkframeInstr = llds_instr(MkframeUinstr, MkframeComment),
find_succeed_labels(Instrs1, map.init, SuccMap),
counter.allocate(KeepFrameLabelNum, !C),
KeepFrameLabel = internal_label(KeepFrameLabelNum, ProcLabel),
keep_nondet_frame(Remain, Instrs2, ProcLabel, KeepFrameLabel,
MkframeUinstr, SuccMap, LayoutLabels, no, yes)
then
list.condense([[LabelInstr], Comments0,
[llds_instr(mkframe(FrameInfo, no), MkframeComment),
llds_instr(label(KeepFrameLabel),
"tail recursion target, nofulljump"),
llds_instr(assign(redoip_slot(lval(curfr)),
const(llconst_code_addr(Redoip))), "")],
Instrs2], Instrs),
Mod = yes
else
Instrs = Instrs0,
Mod = no
).
:- pred nondetstack_setup(list(instruction)::in, nondet_frame_info::out,
code_addr::out, instruction::out, list(instruction)::out) is semidet.
nondetstack_setup(Instrs0, FrameInfo, Redoip, MkframeInstr, Remain) :-
Instrs0 = [MkframeInstr | Remain],
MkframeInstr = llds_instr(mkframe(FrameInfo, yes(Redoip)), _),
FrameInfo = ordinary_frame(_, _).
:- pred find_succeed_labels(list(instruction)::in, tailmap::in, tailmap::out)
is det.
find_succeed_labels([], !SuccMap).
find_succeed_labels([Instr | Instrs], !SuccMap) :-
Instr = llds_instr(Uinstr, _),
( if
Uinstr = label(Label),
opt_util.skip_comments(Instrs, TailInstrs),
opt_util.is_succeed_next(TailInstrs, Between)
then
map.det_insert(Label, Between, !SuccMap)
else
true
),
find_succeed_labels(Instrs, !SuccMap).
:- pred keep_nondet_frame(list(instruction)::in, list(instruction)::out,
proc_label::in, label::in, instr::in, tailmap::in, set_tree234(label)::in,
bool::in, bool::out) is det.
keep_nondet_frame([], [], _, _, _, _, _, !Changed).
keep_nondet_frame([Instr0 | Instrs0], Instrs, ProcLabel, KeepFrameLabel,
PrevInstr, SuccMap, LayoutLabels, !Changed) :-
Instr0 = llds_instr(Uinstr0, Comment),
( if
% Look for nondet style tailcalls which do not need
% a runtime check.
Uinstr0 = llcall(code_label(entry_label(_, ProcLabel)),
code_label(RetLabel), _, _, _, CallModel),
CallModel = call_model_nondet(unchecked_tail_call),
map.search(SuccMap, RetLabel, BetweenIncl),
BetweenIncl = [llds_instr(livevals(_), _), llds_instr(goto(_), _)],
PrevInstr = livevals(Livevals),
not set_tree234.member(RetLabel, LayoutLabels)
then
keep_nondet_frame(Instrs0, Instrs1, ProcLabel, KeepFrameLabel,
Uinstr0, SuccMap, LayoutLabels, !.Changed, _),
!:Changed = yes,
NewComment = Comment ++ " (nondet tailcall)",
Instrs = [
llds_instr(livevals(Livevals), ""),
llds_instr(goto(code_label(KeepFrameLabel)), NewComment)
| Instrs1
]
else
keep_nondet_frame(Instrs0, Instrs1, ProcLabel, KeepFrameLabel,
Uinstr0, SuccMap, LayoutLabels, !Changed),
Instrs = [Instr0 | Instrs1]
).
%-----------------------------------------------------------------------------%
%-----------------------------------------------------------------------------%
:- type frame_block_map(En, Ex) == map(label, frame_block_info(En, Ex)).
:- type det_frame_block_map == frame_block_map(det_entry_info, det_exit_info).
:- type frame_block_info(En, Ex)
---> frame_block_info(
fb_label :: label,
% The label of the first instr.
fb_instrs :: list(instruction),
% The code of the block.
fb_fallen_into :: maybe(label),
% Does the previous block (if any)
% fall through to this block, and if yes,
% what is its label?
fb_jump_dests :: list(label),
% The labels we can jump to
% (not falling through).
fb_fall_dest :: maybe(label),
% The label we fall through to
% (if there is one).
fb_type :: block_type(En, Ex)
).
:- type block_type(EntryInfo, ExitInfo)
---> entry_block(EntryInfo)
; ordinary_block(block_needs_frame, maybe_dummy)
; exit_block(ExitInfo).
:- type maybe_dummy
---> is_not_dummy
; is_post_entry_dummy
; is_pre_exit_dummy.
% Until 30 July 2010, we used to keep a set of reasons *why* a block
% needs a frame. If that info can be useful to you, revert that diff
% in your workspace.
:- type block_needs_frame
---> block_needs_frame
; block_doesnt_need_frame.
:- type det_entry_info
---> det_entry(
int, % The frame size.
string, % The msg of the incr_sp instruction.
stack_incr_kind
).
:- type det_exit_info
---> det_exit( % This block contains det stack teardown
% and goto code.
list(instruction),
% The instr that restores succip (if any).
list(instruction),
% The livevals instr before the goto (if any).
instruction
% The goto instr.
).
:- type nondet_entry_info
---> nondet_entry(
string, % The msg of the mkframe instruction.
int, % The frame size.
code_addr % The initial redoip.
).
:- type nondet_exit_info
---> nondet_plain_exit( % This block contains nondet stack exit code
% that doesn't throw away the stack frame.
list(instruction),
% The livevals instr before the goto (if any).
instruction
% The goto(do_succeed) instr.
)
; nondet_teardown_exit(
% This block contains nondet stack exit code
% that *does* throw away the stack frame.
instruction, % The restore of the succip.
instruction, % The restore of the maxfr.
instruction, % The restore of the curfr.
list(instruction),
% The livevals instr before the goto (if any).
instruction
% The goto(entry(_, _)) instr.
).
:- typeclass block_entry_exit(En, Ex) <= ((En -> Ex), (Ex -> En)) where [
pred detect_entry(list(instruction)::in, list(instruction)::out,
list(instruction)::out, En::out) is semidet,
pred detect_exit(list(instruction)::in, En::in, list(instruction)::out,
list(instruction)::out, list(instruction)::out, Ex::out) is semidet,
func late_setup_code(En) = list(instruction),
func non_teardown_exit_code(Ex) = list(instruction),
func describe_entry(En) = string,
func describe_exit(maybe(proc_label), Ex) = string
].
:- instance block_entry_exit(det_entry_info, det_exit_info) where [
pred(detect_entry/4) is detect_det_entry,
pred(detect_exit/6) is detect_det_exit,
func(late_setup_code/1) is det_late_setup,
func(non_teardown_exit_code/1) is det_non_teardown_exit_code,
func(describe_entry/1) is describe_det_entry,
func(describe_exit/2) is describe_det_exit
].
:- instance block_entry_exit(nondet_entry_info, nondet_exit_info) where [
pred(detect_entry/4) is detect_nondet_entry,
pred(detect_exit/6) is detect_nondet_exit,
func(late_setup_code/1) is nondet_late_setup,
func(non_teardown_exit_code/1) is nondet_non_teardown_exit_code,
func(describe_entry/1) is describe_nondet_entry,
func(describe_exit/2) is describe_nondet_exit
].
%-----------------------------------------------------------------------------%
% Add labels to the given instruction sequence so that
% every basic block has labels around it.
%
:- pred divide_into_basic_blocks(list(instruction)::in, proc_label::in,
list(instruction)::out, counter::in, counter::out) is det.
divide_into_basic_blocks([], _, [], !C).
% Control can fall off the end of a procedure if that procedure
% ends with a call to another procedure that cannot succeed.
% This is the only situation in which the base case can be reached.
divide_into_basic_blocks([Instr0 | Instrs0], ProcLabel, Instrs, !C) :-
Instr0 = llds_instr(Uinstr0, _Comment),
CanBranchAway = opt_util.can_instr_branch_away(Uinstr0),
(
CanBranchAway = yes,
(
Instrs0 = [Instr1 | _],
( if Instr1 = llds_instr(label(_), _) then
divide_into_basic_blocks(Instrs0, ProcLabel, Instrs1, !C),
Instrs = [Instr0 | Instrs1]
else
counter.allocate(N, !C),
NewLabel = internal_label(N, ProcLabel),
NewInstr = llds_instr(label(NewLabel), ""),
divide_into_basic_blocks(Instrs0, ProcLabel, Instrs1, !C),
Instrs = [Instr0, NewInstr | Instrs1]
)
;
Instrs0 = [],
Instrs = [Instr0]
)
;
CanBranchAway = no,
divide_into_basic_blocks(Instrs0, ProcLabel, Instrs1, !C),
Instrs = [Instr0 | Instrs1]
).
:- pred flatten_block_seq(list(label)::in, frame_block_map(En, Ex)::in,
list(instruction)::out) is det.
flatten_block_seq([], _, []).
flatten_block_seq([Label | Labels], BlockMap, Instrs) :-
flatten_block_seq(Labels, BlockMap, RestInstrs),
map.lookup(BlockMap, Label, BlockInfo),
BlockInstrs = BlockInfo ^ fb_instrs,
( if
list.split_last(BlockInstrs, MostInstrs, LastInstr),
Labels = [NextLabel | _],
LastInstr = llds_instr(goto(code_label(NextLabel)), _)
then
% Optimize away the redundant goto, which we probably introduced.
% The next invocation of jumpopt would also do this, but doing it here
% is cheaper and may let us reach a fixpoint in the optimization
% sequence earlier.
Instrs = MostInstrs ++ RestInstrs
else
Instrs = BlockInstrs ++ RestInstrs
).
%-----------------------------------------------------------------------------%
% This type is explained in the big comment in the body of
% build_frame_block_map below.
:- type pre_exit_dummy_label_map == map(label, label).
% Given an instruction list in which labels mark the start of every
% basic block, divide it up into basic blocks of one of three types:
%
% - entry blocks, blocks that contain only stack setup instructions
% (incr_sp and assignment of succip to the bottom stack slot);
%
% - ordinary blocks that contain neither a stack setup nor a
% stack teardown;
%
% - exit blocks that remove an existing stack frame.
%
% For such each block, create a frame_block_info structure that gives the
% label starting the block, the instructions in the block, and its
% type. Two of the fields of the frame_block_info structure are filled in
% with dummy values; they will be filled in for real later.
%
% Put these frame_block_info structures into a table indexed by the label,
% and return the sequence of labels of the blocks in their original
% order.
%
:- pred build_frame_block_map(list(instruction)::in, En::in,
list(label)::out, maybe(label)::in, maybe(label)::in, proc_label::in,
frame_block_map(En, Ex)::in, frame_block_map(En, Ex)::out,
pred_map::in, pred_map::out, counter::in, counter::out,
pre_exit_dummy_label_map::in, pre_exit_dummy_label_map::out) is det
<= block_entry_exit(En, Ex).
build_frame_block_map([], _, [], _, _, _, !BlockMap, !PredMap, !C,
!PreExitDummyLabelMap).
build_frame_block_map([Instr0 | Instrs0], EntryInfo, LabelSeq,
MaybePrevLabel, FallInto, ProcLabel, !BlockMap, !PredMap, !C,
!PreExitDummyLabelMap) :-
( if Instr0 = llds_instr(label(Label), _) then
(
MaybePrevLabel = yes(PrevLabel),
map.det_insert(Label, PrevLabel, !PredMap)
;
MaybePrevLabel = no
),
( if
detect_entry(Instrs0, EntryInstrs, Instrs1, EntryInfo)
then
% Create a block with just the entry instructions in it,
% followed by an empty block. The reason why we need the empty
% block is that process_frame_delay below doesn't handle any
% transition from entry blocks directly to exit blocks.
% Fixing that would be complicated; this fix is simpler.
%
% We would like to put EmptyLabel *after* FallThroughLabel
% to make the next invocation of labelopt eliminate EmptyLabel
% rather than FallThroughLabel, but doing that would require
% updating LabelSeq and BlockMap.
counter.allocate(EmptyN, !C),
EmptyLabel = internal_label(EmptyN, ProcLabel),
% The fb_jump_dests and fb_fall_dest fields are only dummies.
FallThroughToEmptyInstr =
llds_instr(goto(code_label(EmptyLabel)), "fall through"),
BlockInfo = frame_block_info(Label,
[Instr0 | EntryInstrs] ++ [FallThroughToEmptyInstr],
FallInto, [], no, entry_block(EntryInfo)),
% Ensure that the left over, non-entry part of the original block
% starts with a label, and that the empty block ends with a goto
% that falls through to this label.
( if
Instrs1 = [Instr1 | _],
Instr1 = llds_instr(label(NextLabelPrime), _)
then
NextLabel = NextLabelPrime,
Instrs2 = Instrs1
else
counter.allocate(N, !C),
NextLabel = internal_label(N, ProcLabel),
NextLabelInstr = llds_instr(label(NextLabel), ""),
Instrs2 = [NextLabelInstr | Instrs1]
),
EmptyLabelInstr = llds_instr(label(EmptyLabel), ""),
FallThroughFromEmptyInstr =
llds_instr(goto(code_label(NextLabel)), "fall through"),
% The fb_jump_dests and fb_fall_dest fields are only dummies.
EmptyBlockType = ordinary_block(block_doesnt_need_frame,
is_post_entry_dummy),
EmptyBlockInfo = frame_block_info(EmptyLabel,
[EmptyLabelInstr, FallThroughFromEmptyInstr],
yes(Label), [], no, EmptyBlockType),
build_frame_block_map(Instrs2, EntryInfo, LabelSeq0,
yes(EmptyLabel), yes(EmptyLabel), ProcLabel, !BlockMap,
!PredMap, !C, !PreExitDummyLabelMap),
map.det_insert(Label, BlockInfo, !BlockMap),
map.det_insert(EmptyLabel, EmptyBlockInfo, !BlockMap),
LabelSeq = [Label, EmptyLabel | LabelSeq0]
else if
detect_exit(Instrs0, EntryInfo, Extra, ExitInstrs,
Remain, ExitInfo)
then
% We always insert an ordinary block before the exit block,
% because doing otherwise could lead to a violation of our
% invariant that exit blocks never *need* a stack frame
% in cases where the redoip of a nondet frame is assigned
% the label of the exit block. By inserting a dummy block
% before the exit block if necessary, we ensure that the redoip
% points not to the exit block but to the ordinary block
% preceding it.
%
% However, having other blocks jump to a pre_exit dummy block
% instead of the exit block loses opportunities for optimization.
% This is because we may (and typically will) fall into the
% pre_exit dummy block from an ordinary block that needs a stack
% frame, and this requirement is propagated to the pre_exit dummy
% block by propagate_frame_requirement_to_successors, which will
% cause propagate_frame_requirement_to_predecessors to propagate
% that requirement to blocks that don't actually need a stack
% frame. This is why in the is_pre_exit_dummy case below we record
% the mapping from the label of the pre_exit dummy block to the
% label of the exit block, so that we can alter instructions
% that jump to the first label to proceed to the second. Since
% there is no code between those two labels (except a dummy goto
% instruction that implements the fallthrough), this is safe.
% To avoid violating the invariant mentioned at the top of this
% comment, we don't substitute labels used as code addresses
% in assignments to redoip slots.
counter.allocate(N, !C),
ExitLabel = internal_label(N, ProcLabel),
compute_block_needs_frame(Label, Extra, NeedsFrame),
FallThroughInstr =
llds_instr(goto(code_label(ExitLabel)), "fall through"),
% The fb_jump_dests and fb_fall_dest fields are only dummies.
(
Extra = [],
expect(unify(NeedsFrame, block_doesnt_need_frame), $pred,
"[] needs frame"),
map.det_insert(Label, ExitLabel, !PreExitDummyLabelMap),
ExtraBlockType = ordinary_block(NeedsFrame, is_pre_exit_dummy)
;
Extra = [_ | _],
ExtraBlockType = ordinary_block(NeedsFrame, is_not_dummy)
),
ExtraInstrs = [Instr0 | Extra] ++ [FallThroughInstr],
ExtraInfo = frame_block_info(Label, ExtraInstrs, FallInto,
[], no, ExtraBlockType),
ExitLabelInstr = llds_instr(label(ExitLabel), ""),
LabelledBlock = [ExitLabelInstr | ExitInstrs],
% The fb_jump_dests and fb_fall_dest fields are only dummies.
ExitBlockInfo = frame_block_info(ExitLabel, LabelledBlock,
yes(Label), [], no, exit_block(ExitInfo)),
map.det_insert(ExitLabel, Label, !PredMap),
build_frame_block_map(Remain, EntryInfo, LabelSeq0, yes(ExitLabel),
no, ProcLabel, !BlockMap, !PredMap, !C, !PreExitDummyLabelMap),
map.det_insert(ExitLabel, ExitBlockInfo, !BlockMap),
map.det_insert(Label, ExtraInfo, !BlockMap),
LabelSeq = [Label, ExitLabel | LabelSeq0]
else
opt_util.skip_to_next_label(Instrs0, Block, Instrs1),
compute_block_needs_frame(Label, Block, NeedsFrame),
BlockInstrs = [Instr0 | Block],
% The fb_jump_dests and fb_fall_dest fields are only dummies.
BlockInfo = frame_block_info(Label, BlockInstrs, FallInto,
[], no, ordinary_block(NeedsFrame, is_not_dummy)),
( if list.last(BlockInstrs, LastBlockInstr) then
LastBlockInstr = llds_instr(LastBlockUinstr, _),
NextFallIntoBool =
opt_util.can_instr_fall_through(LastBlockUinstr),
(
NextFallIntoBool = yes,
NextFallInto = yes(Label)
;
NextFallIntoBool = no,
NextFallInto = no
)
else
NextFallInto = yes(Label)
),
build_frame_block_map(Instrs1, EntryInfo, LabelSeq0, yes(Label),
NextFallInto, ProcLabel, !BlockMap, !PredMap, !C,
!PreExitDummyLabelMap),
map.det_insert(Label, BlockInfo, !BlockMap),
LabelSeq = [Label | LabelSeq0]
)
else
unexpected($pred, "block does not start with label")
).
%-----------------------------------------------------------------------------%
% Does the given code start with a setup of a det stack frame? If yes,
% return the size of the frame and two instruction sequences,
% Setup and Others ++ Remain. Setup is the instruction sequence
% that sets up the det stack frame, Others is a sequence of
% non-interfering instructions that were interspersed with Setup
% but can be moved after Setup, and Remain is all remaining instructions.
%
:- pred detect_det_entry(list(instruction)::in, list(instruction)::out,
list(instruction)::out, det_entry_info::out) is semidet.
detect_det_entry(Instrs0, Setup, Others ++ Remain, EntryInfo) :-
opt_util.gather_comments(Instrs0, Others0, Instrs1),
Instrs1 = [SetupInstr1 | Instrs2],
SetupInstr1 = llds_instr(incr_sp(FrameSize, Msg, Kind), _),
detstack_setup(Instrs2, FrameSize, SetupInstr2, Others0, Others, Remain),
Setup = [SetupInstr1, SetupInstr2],
EntryInfo = det_entry(FrameSize, Msg, Kind).
:- pred detstack_setup(list(instruction)::in, int::in, instruction::out,
list(instruction)::in, list(instruction)::out, list(instruction)::out)
is semidet.
detstack_setup([Instr0 | Instrs0], FrameSize, Setup, !Others, Remain) :-
Instr0 = llds_instr(Uinstr0, _),
( if Uinstr0 = assign(Lval, Rval) then
( if
Lval = stackvar(FrameSize),
Rval = lval(succip)
then
Setup = Instr0,
Remain = Instrs0
else if
Lval \= succip,
Lval \= stackvar(FrameSize)
then
!:Others = !.Others ++ [Instr0],
detstack_setup(Instrs0, FrameSize, Setup, !Others, Remain)
else
fail
)
else if Uinstr0 = comment(_) then
!:Others = !.Others ++ [Instr0],
detstack_setup(Instrs0, FrameSize, Setup, !Others, Remain)
else
fail
).
:- pred detect_nondet_entry(list(instruction)::in, list(instruction)::out,
list(instruction)::out, nondet_entry_info::out) is semidet.
detect_nondet_entry(Instrs0, [MkframeInstr], Remain, EntryInfo) :-
Instrs0 = [MkframeInstr | Remain],
MkframeInstr = llds_instr(mkframe(FrameInfo, MaybeRedoip), _),
% We could allow MaybeRedoip to be `no', and search for the instruction
% that sets the redoip of the new frame. That is left for future work.
MaybeRedoip = yes(Redoip),
% If the initial mkframe sets the redoip to something other than do_fail,
% then even this entry block needs a stack frame, so frameopt cannot do
% anything.
Redoip = do_fail,
FrameInfo = ordinary_frame(Msg, Size),
EntryInfo = nondet_entry(Msg, Size, Redoip).
%-----------------------------------------------------------------------------%
:- pred detect_det_exit(list(instruction)::in, det_entry_info::in,
list(instruction)::out, list(instruction)::out, list(instruction)::out,
det_exit_info::out) is semidet.
detect_det_exit(Instrs0, EntryInfo, Extra, ExitInstrs, Remain, ExitInfo) :-
EntryInfo = det_entry(FrameSize, _Msg, _),
detstack_teardown(Instrs0, FrameSize, Extra, SuccipRestore, Decrsp,
Livevals, Goto, Remain),
ExitInstrs = SuccipRestore ++ Decrsp ++ Livevals ++ [Goto],
ExitInfo = det_exit(SuccipRestore, Livevals, Goto).
% Does the following block contain a teardown of a det stack frame,
% and a proceed or tailcall? If yes, we return
%
% - the instruction that restores succip as Succip
% - the decr_sp instruction as Decrsp
% - the livevals instruction as Livevals
% - the goto instruction as Goto
%
% The first three can appear in any order or may be missing, due to
% value numbering. This is also why we allow the teardown instructions
% to be interleaved with instructions that do not access the stack;
% any such instructions are returned as Extra. Remain is all the
% instructions after the teardown.
%
:- pred detstack_teardown(list(instruction)::in, int::in,
list(instruction)::out, list(instruction)::out,
list(instruction)::out, list(instruction)::out,
instruction::out, list(instruction)::out) is semidet.
detstack_teardown([Instr0 | Instrs0], FrameSize, Extra, SuccipRestore, Decrsp,
Livevals, Goto, Remain) :-
( if
Instr0 = llds_instr(label(_), _)
then
fail
else if
detstack_teardown_2([Instr0 | Instrs0], FrameSize,
[], ExtraPrime, [], SuccipRestorePrime, [], DecrspPrime,
[], LivevalsPrime, GotoPrime, RemainPrime)
then
Extra = ExtraPrime,
SuccipRestore = SuccipRestorePrime,
Decrsp = DecrspPrime,
Livevals = LivevalsPrime,
Goto = GotoPrime,
Remain = RemainPrime
else
detstack_teardown(Instrs0, FrameSize, Extra1, SuccipRestore, Decrsp,
Livevals, Goto, Remain),
Extra = [Instr0 | Extra1]
).
:- pred detstack_teardown_2(list(instruction)::in, int::in,
list(instruction)::in, list(instruction)::out,
list(instruction)::in, list(instruction)::out,
list(instruction)::in, list(instruction)::out,
list(instruction)::in, list(instruction)::out,
instruction::out, list(instruction)::out) is semidet.
detstack_teardown_2(Instrs0, FrameSize, !Extra, !SuccipRestore, !Decrsp,
!Livevals, Goto, Remain) :-
opt_util.skip_comments(Instrs0, Instrs1),
Instrs1 = [Instr1 | Instrs2],
Instr1 = llds_instr(Uinstr1, _),
% XXX allow other instruction types in Extras, e.g. incr_hp
(
Uinstr1 = assign(Lval, Rval),
( if
Lval = succip,
Rval = lval(stackvar(FrameSize))
then
!.SuccipRestore = [],
!.Decrsp = [],
!:SuccipRestore = [Instr1],
detstack_teardown_2(Instrs2, FrameSize, !Extra, !SuccipRestore,
!Decrsp, !Livevals, Goto, Remain)
else
opt_util.lval_refers_stackvars(Lval) = no,
opt_util.rval_refers_stackvars(Rval) = no,
!:Extra = !.Extra ++ [Instr1],
detstack_teardown_2(Instrs2, FrameSize, !Extra, !SuccipRestore,
!Decrsp, !Livevals, Goto, Remain)
)
;
Uinstr1 = decr_sp(FrameSize),
!.Decrsp = [],
!:Decrsp = [Instr1],
detstack_teardown_2(Instrs2, FrameSize, !Extra, !SuccipRestore,
!Decrsp, !Livevals, Goto, Remain)
;
Uinstr1 = livevals(_),
!.Livevals = [],
!:Livevals = [Instr1],
detstack_teardown_2(Instrs2, FrameSize, !Extra, !SuccipRestore,
!Decrsp, !Livevals, Goto, Remain)
;
Uinstr1 = goto(_),
!.Decrsp = [_],
Goto = Instr1,
Remain = Instrs2
).
:- pred detect_nondet_exit(list(instruction)::in, nondet_entry_info::in,
list(instruction)::out, list(instruction)::out, list(instruction)::out,
nondet_exit_info::out) is semidet.
detect_nondet_exit(Instrs0, _EntryInfo, Extra, ExitInstrs, Remain, ExitInfo) :-
nondetstack_teardown(Instrs0, Extra, SuccipRestore, Maxfr, Curfr,
Livevals, Goto, GotoTarget, Remain),
ExitInstrs = SuccipRestore ++ Maxfr ++ Curfr ++ Livevals ++ [Goto],
(
Curfr = [],
% MR_succeed refers to the current stack frame, so it is valid
% only if we haven't thrown away the stack frame yet by resetting
% curfr.
Maxfr = [],
SuccipRestore = [],
GotoTarget = do_succeed(_),
ExitInfo = nondet_plain_exit(Livevals, Goto)
;
Curfr = [CurfrInstr],
% If we *have* thrown away the current stack frame, we can exit
% only via tailcall, and in that case we ought to have also reset
% maxfr and succip.
Maxfr = [MaxfrInstr],
SuccipRestore = [SuccipRestoreInstr],
( GotoTarget = code_label(entry_label(_, _))
; GotoTarget = code_imported_proc(_)
),
ExitInfo = nondet_teardown_exit(SuccipRestoreInstr,
MaxfrInstr, CurfrInstr, Livevals, Goto)
).
% Does the following block contain a succeed from a nondet stack frame?
% If yes, we return
%
% - the livevals instruction (if any) as Livevals
% - the goto instruction as Goto
%
% These may be preceded by instructions that do not access the stack;
% any such instructions are returned as Extra. Remain is all the
% instructions after the succeed.
%
:- pred nondetstack_teardown(list(instruction)::in, list(instruction)::out,
list(instruction)::out, list(instruction)::out,
list(instruction)::out, list(instruction)::out,
instruction::out, code_addr::out, list(instruction)::out) is semidet.
nondetstack_teardown([Instr0 | Instrs0], Extra, SuccipRestore, Maxfr, Curfr,
Livevals, Goto, GotoTarget, Remain) :-
( if
Instr0 = llds_instr(label(_), _)
then
fail
else if
nondetstack_teardown_2([Instr0 | Instrs0], [], ExtraPrime,
[], SuccipRestorePrime, [], MaxfrPrime, [], CurfrPrime,
[], LivevalsPrime, GotoPrime, GotoTargetPrime, RemainPrime)
then
Extra = ExtraPrime,
SuccipRestore = SuccipRestorePrime,
Maxfr = MaxfrPrime,
Curfr = CurfrPrime,
Livevals = LivevalsPrime,
Goto = GotoPrime,
GotoTarget = GotoTargetPrime,
Remain = RemainPrime
else
nondetstack_teardown(Instrs0, Extra1, SuccipRestore, Maxfr, Curfr,
Livevals, Goto, GotoTarget, Remain),
Extra = [Instr0 | Extra1]
).
:- pred nondetstack_teardown_2(list(instruction)::in,
list(instruction)::in, list(instruction)::out,
list(instruction)::in, list(instruction)::out,
list(instruction)::in, list(instruction)::out,
list(instruction)::in, list(instruction)::out,
list(instruction)::in, list(instruction)::out,
instruction::out, code_addr::out, list(instruction)::out) is semidet.
nondetstack_teardown_2(Instrs0, !Extra, !SuccipRestore, !Maxfr, !Curfr,
!Livevals, Goto, GotoTarget, Remain) :-
opt_util.skip_comments(Instrs0, Instrs1),
Instrs1 = [Instr1 | Instrs2],
Instr1 = llds_instr(Uinstr1, _),
% XXX allow other instruction types in Extras, e.g. incr_hp
(