#      CC.pm
#
#      Copyright (c) 1996, 1997, 1998 Malcolm Beattie
#
#      You may distribute under the terms of either the GNU General Public
#      License or the Artistic License, as specified in the README file.
#
package B::CC;
use strict;
use B qw(main_start main_root class comppadlist peekop svref_2object
	timing_info);
use B::C qw(save_unused_subs objsym init_sections
	    output_all output_boilerplate output_main);
use B::Bblock qw(find_leaders);
use B::Stackobj qw(:types :flags);

# These should probably be elsewhere
# Flags for $op->flags
sub OPf_LIST () { 1 }
sub OPf_KNOW () { 2 }
sub OPf_MOD () { 32 }
sub OPf_STACKED () { 64 }
sub OPf_SPECIAL () { 128 }
# op-specific flags for $op->private 
sub OPpASSIGN_BACKWARDS () { 64 }
sub OPpLVAL_INTRO () { 128 }
sub OPpDEREF_AV () { 32 }
sub OPpDEREF_HV () { 64 }
sub OPpDEREF () { OPpDEREF_AV|OPpDEREF_HV }
sub OPpFLIP_LINENUM () { 64 }
sub G_ARRAY () { 1 }
# cop.h
sub CXt_NULL () { 0 }
sub CXt_SUB () { 1 }
sub CXt_EVAL () { 2 }
sub CXt_LOOP () { 3 }
sub CXt_SUBST () { 4 }
sub CXt_BLOCK () { 5 }

my $module;		# module name (when compiled with -m)
my %done;		# hash keyed by $$op of leaders of basic blocks
			# which have already been done.
my $leaders;		# ref to hash of basic block leaders. Keys are $$op
			# addresses, values are the $op objects themselves.
my @bblock_todo;	# list of leaders of basic blocks that need visiting
			# sometime.
my @cc_todo;		# list of tuples defining what PP code needs to be
			# saved (e.g. CV, main or PMOP repl code). Each tuple
			# is [$name, $root, $start, @padlist]. PMOP repl code
			# tuples inherit padlist.
my @stack;		# shadows perl's stack when contents are known.
			# Values are objects derived from class B::Stackobj
my @pad;		# Lexicals in current pad as Stackobj-derived objects
my @padlist;		# Copy of current padlist so PMOP repl code can find it
my @cxstack;		# Shadows the (compile-time) cxstack for next,last,redo
my $jmpbuf_ix = 0;	# Next free index for dynamically allocated jmpbufs
my %constobj;		# OP_CONST constants as Stackobj-derived objects
			# keyed by $$sv.
my $need_freetmps = 0;	# We may postpone FREETMPS to the end of each basic
			# block or even to the end of each loop of blocks,
			# depending on optimisation options.
my $know_op = 0;	# Set when C variable op already holds the right op
			# (from an immediately preceding DOOP(ppname)).
my $errors = 0;		# Number of errors encountered
my %skip_stack;		# Hash of PP names which don't need write_back_stack
my %skip_lexicals;	# Hash of PP names which don't need write_back_lexicals
my %skip_invalidate;	# Hash of PP names which don't need invalidate_lexicals
my %ignore_op;		# Hash of ops which do nothing except returning op_next

BEGIN {
    foreach (qw(pp_scalar pp_regcmaybe pp_lineseq pp_scope pp_null)) {
	$ignore_op{$_} = 1;
    }
}

my @unused_sub_packages; # list of packages (given by -u options) to search
			 # explicitly and save every sub we find there, even
			 # if apparently unused (could be only referenced from
			 # an eval "" or from a $SIG{FOO} = "bar").

my ($module_name);
my ($debug_op, $debug_stack, $debug_cxstack, $debug_pad, $debug_runtime,
    $debug_shadow, $debug_queue, $debug_lineno, $debug_timings);

# Optimisation options. On the command line, use hyphens instead of
# underscores for compatibility with gcc-style options. We use
# underscores here because they are OK in (strict) barewords.
my ($freetmps_each_bblock, $freetmps_each_loop, $omit_taint);
my %optimise = (freetmps_each_bblock	=> \$freetmps_each_bblock,
		freetmps_each_loop	=> \$freetmps_each_loop,
		omit_taint		=> \$omit_taint);
# perl patchlevel to generate code for (defaults to current patchlevel)
my $patchlevel = int(0.5 + 1000 * ($]  - 5));

# Could rewrite push_runtime() and output_runtime() to use a
# temporary file if memory is at a premium.
my $ppname;		# name of current fake PP function
my $runtime_list_ref;
my $declare_ref;	# Hash ref keyed by C variable type of declarations.

my @pp_list;		# list of [$ppname, $runtime_list_ref, $declare_ref]
			# tuples to be written out.

my ($init, $decl);

sub init_hash { map { $_ => 1 } @_ }

#
# Initialise the hashes for the default PP functions where we can avoid
# either write_back_stack, write_back_lexicals or invalidate_lexicals.
#
%skip_lexicals = init_hash qw(pp_enter pp_enterloop);
%skip_invalidate = init_hash qw(pp_enter pp_enterloop);

sub debug {
    if ($debug_runtime) {
	warn(@_);
    } else {
	runtime(map { chomp; "/* $_ */"} @_);
    }
}

sub declare {
    my ($type, $var) = @_;
    push(@{$declare_ref->{$type}}, $var);
}

sub push_runtime {
    push(@$runtime_list_ref, @_);
    warn join("\n", @_) . "\n" if $debug_runtime;
}

sub save_runtime {
    push(@pp_list, [$ppname, $runtime_list_ref, $declare_ref]);
}

sub output_runtime {
    my $ppdata;
    print qq(#include "cc_runtime.h"\n);
    foreach $ppdata (@pp_list) {
	my ($name, $runtime, $declare) = @$ppdata;
	print "\nstatic\nPP($name)\n{\n";
	my ($type, $varlist, $line);
	while (($type, $varlist) = each %$declare) {
	    print "\t$type ", join(", ", @$varlist), ";\n";
	}
	foreach $line (@$runtime) {
	    print $line, "\n";
	}
	print "}\n";
    }
}

sub runtime {
    my $line;
    foreach $line (@_) {
	push_runtime("\t$line");
    }
}

sub init_pp {
    $ppname = shift;
    $runtime_list_ref = [];
    $declare_ref = {};
    runtime("djSP;");
    declare("I32", "oldsave");
    declare("SV", "**svp");
    map { declare("SV", "*$_") } qw(sv src dst left right);
    declare("MAGIC", "*mg");
    $decl->add("static OP * $ppname _((ARGSproto));");
    debug "init_pp: $ppname\n" if $debug_queue;
}

# Initialise runtime_callback function for Stackobj class
BEGIN { B::Stackobj::set_callback(\&runtime) }

# Initialise saveoptree_callback for B::C class
sub cc_queue {
    my ($name, $root, $start, @pl) = @_;
    debug "cc_queue: name $name, root $root, start $start, padlist (@pl)\n"
	if $debug_queue;
    if ($name eq "*ignore*") {
	$name = 0;
    } else {
	push(@cc_todo, [$name, $root, $start, (@pl ? @pl : @padlist)]);
    }
    my $fakeop = new B::FAKEOP ("next" => 0, sibling => 0, ppaddr => $name);
    $start = $fakeop->save;
    debug "cc_queue: name $name returns $start\n" if $debug_queue;
    return $start;
}
BEGIN { B::C::set_callback(\&cc_queue) }

sub valid_int { $_[0]->{flags} & VALID_INT }
sub valid_double { $_[0]->{flags} & VALID_DOUBLE }
sub valid_numeric { $_[0]->{flags} & (VALID_INT | VALID_DOUBLE) }
sub valid_sv { $_[0]->{flags} & VALID_SV }

sub top_int { @stack ? $stack[-1]->as_int : "TOPi" }
sub top_double { @stack ? $stack[-1]->as_double : "TOPn" }
sub top_numeric { @stack ? $stack[-1]->as_numeric : "TOPn" }
sub top_sv { @stack ? $stack[-1]->as_sv : "TOPs" }
sub top_bool { @stack ? $stack[-1]->as_numeric : "SvTRUE(TOPs)" }

sub pop_int { @stack ? (pop @stack)->as_int : "POPi" }
sub pop_double { @stack ? (pop @stack)->as_double : "POPn" }
sub pop_numeric { @stack ? (pop @stack)->as_numeric : "POPn" }
sub pop_sv { @stack ? (pop @stack)->as_sv : "POPs" }
sub pop_bool {
    if (@stack) {
	return ((pop @stack)->as_numeric);
    } else {
	# Careful: POPs has an auto-decrement and SvTRUE evaluates
	# its argument more than once.
	runtime("sv = POPs;");
	return "SvTRUE(sv)";
    }
}

sub write_back_lexicals {
    my $avoid = shift || 0;
    debug "write_back_lexicals($avoid) called from @{[(caller(1))[3]]}\n"
	if $debug_shadow;
    my $lex;
    foreach $lex (@pad) {
	next unless ref($lex);
	$lex->write_back unless $lex->{flags} & $avoid;
    }
}

sub write_back_stack {
    my $obj;
    return unless @stack;
    runtime(sprintf("EXTEND(sp, %d);", scalar(@stack)));
    foreach $obj (@stack) {
	runtime(sprintf("PUSHs((SV*)%s);", $obj->as_sv));
    }
    @stack = ();
}

sub invalidate_lexicals {
    my $avoid = shift || 0;
    debug "invalidate_lexicals($avoid) called from @{[(caller(1))[3]]}\n"
	if $debug_shadow;
    my $lex;
    foreach $lex (@pad) {
	next unless ref($lex);
	$lex->invalidate unless $lex->{flags} & $avoid;
    }
}

sub reload_lexicals {
    my $lex;
    foreach $lex (@pad) {
	next unless ref($lex);
	my $type = $lex->{type};
	if ($type == T_INT) {
	    $lex->as_int;
	} elsif ($type == T_DOUBLE) {
	    $lex->as_double;
	} else {
	    $lex->as_sv;
	}
    }
}

{
    package B::Pseudoreg;
    #
    # This class allocates pseudo-registers (OK, so they're C variables).
    #
    my %alloc;		# Keyed by variable name. A value of 1 means the
			# variable has been declared. A value of 2 means
			# it's in use.
    
    sub new_scope { %alloc = () }
    
    sub new ($$$) {
	my ($class, $type, $prefix) = @_;
	my ($ptr, $i, $varname, $status, $obj);
	$prefix =~ s/^(\**)//;
	$ptr = $1;
	$i = 0;
	do {
	    $varname = "$prefix$i";
	    $status = $alloc{$varname};
	} while $status == 2;
	if ($status != 1) {
	    # Not declared yet
	    B::CC::declare($type, "$ptr$varname");
	    $alloc{$varname} = 2;	# declared and in use
	}
	$obj = bless \$varname, $class;
	return $obj;
    }
    sub DESTROY {
	my $obj = shift;
	$alloc{$$obj} = 1; # no longer in use but still declared
    }
}
{
    package B::Shadow;
    #
    # This class gives a standard API for a perl object to shadow a
    # C variable and only generate reloads/write-backs when necessary.
    #
    # Use $obj->load($foo) instead of runtime("shadowed_c_var = foo").
    # Use $obj->write_back whenever shadowed_c_var needs to be up to date.
    # Use $obj->invalidate whenever an unknown function may have
    # set shadow itself.

    sub new {
	my ($class, $write_back) = @_;
	# Object fields are perl shadow variable, validity flag
	# (for *C* variable) and callback sub for write_back
	# (passed perl shadow variable as argument).
	bless [undef, 1, $write_back], $class;
    }
    sub load {
	my ($obj, $newval) = @_;
	$obj->[1] = 0;		# C variable no longer valid
	$obj->[0] = $newval;
    }
    sub write_back {
	my $obj = shift;
	if (!($obj->[1])) {
	    $obj->[1] = 1;	# C variable will now be valid
	    &{$obj->[2]}($obj->[0]);
	}
    }
    sub invalidate { $_[0]->[1] = 0 } # force C variable to be invalid
}
my $curcop = new B::Shadow (sub {
    my $opsym = shift->save;
    runtime("PL_curcop = (COP*)$opsym;");
});

#
# Context stack shadowing. Mimics stuff in pp_ctl.c, cop.h and so on.
#
sub dopoptoloop {
    my $cxix = $#cxstack;
    while ($cxix >= 0 && $cxstack[$cxix]->{type} != CXt_LOOP) {
	$cxix--;
    }
    debug "dopoptoloop: returning $cxix" if $debug_cxstack;
    return $cxix;
}

sub dopoptolabel {
    my $label = shift;
    my $cxix = $#cxstack;
    while ($cxix >= 0 && $cxstack[$cxix]->{type} != CXt_LOOP
	   && $cxstack[$cxix]->{label} ne $label) {
	$cxix--;
    }
    debug "dopoptolabel: returning $cxix" if $debug_cxstack;
    return $cxix;
}

sub error {
    my $format = shift;
    my $file = $curcop->[0]->filegv->SV->PV;
    my $line = $curcop->[0]->line;
    $errors++;
    if (@_) {
	warn sprintf("%s:%d: $format\n", $file, $line, @_);
    } else {
	warn sprintf("%s:%d: %s\n", $file, $line, $format);
    }
}

#
# Load pad takes (the elements of) a PADLIST as arguments and loads
# up @pad with Stackobj-derived objects which represent those lexicals.
# If/when perl itself can generate type information (my int $foo) then
# we'll take advantage of that here. Until then, we'll use various hacks
# to tell the compiler when we want a lexical to be a particular type
# or to be a register.
#
sub load_pad {
    my ($namelistav, $valuelistav) = @_;
    @padlist = @_;
    my @namelist = $namelistav->ARRAY;
    my @valuelist = $valuelistav->ARRAY;
    my $ix;
    @pad = ();
    debug "load_pad: $#namelist names, $#valuelist values\n" if $debug_pad;
    # Temporary lexicals don't get named so it's possible for @valuelist
    # to be strictly longer than @namelist. We count $ix up to the end of
    # @valuelist but index into @namelist for the name. Any temporaries which
    # run off the end of @namelist will make $namesv undefined and we treat
    # that the same as having an explicit SPECIAL sv_undef object in @namelist.
    # [XXX If/when @_ becomes a lexical, we must start at 0 here.]
    for ($ix = 1; $ix < @valuelist; $ix++) {
	my $namesv = $namelist[$ix];
	my $type = T_UNKNOWN;
	my $flags = 0;
	my $name = "tmp$ix";
	my $class = class($namesv);
	if (!defined($namesv) || $class eq "SPECIAL") {
	    # temporaries have &PL_sv_undef instead of a PVNV for a name
	    $flags = VALID_SV|TEMPORARY|REGISTER;
	} else {
	    if ($namesv->PV =~ /^\$(.*)_([di])(r?)$/) {
		$name = $1;
		if ($2 eq "i") {
		    $type = T_INT;
		    $flags = VALID_SV|VALID_INT;
		} elsif ($2 eq "d") {
		    $type = T_DOUBLE;
		    $flags = VALID_SV|VALID_DOUBLE;
		}
		$flags |= REGISTER if $3;
	    }
	}
	$pad[$ix] = new B::Stackobj::Padsv ($type, $flags, $ix,
					    "i_$name", "d_$name");
	declare("IV", $type == T_INT ? "i_$name = 0" : "i_$name");
	declare("double", $type == T_DOUBLE ? "d_$name = 0" : "d_$name");
	debug sprintf("PL_curpad[$ix] = %s\n", $pad[$ix]->peek) if $debug_pad;
    }
}

#
# Debugging stuff
#
sub peek_stack { sprintf "stack = %s\n", join(" ", map($_->minipeek, @stack)) }

#
# OP stuff
#

sub label {