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Implement lexical => local lowering.
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@jnthn
jnthn committed Apr 3, 2014
1 parent 44181ad commit d062aa3
Showing 1 changed file with 146 additions and 11 deletions.
157 changes: 146 additions & 11 deletions src/NQP/Optimizer.nqp
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Expand Up @@ -15,18 +15,99 @@ class NQP::Optimizer {
# immediate block or a declaration block.
has %!usages_inner;

# If lowering is, for some reason, poisened.
has $!poisoned;

method add_decl($var) {
%!decls{$var.name} := $var;
}

method add_usage($var) {
my @usages := %!usages_flat{$var.name};
my $name := $var.name;
my @usages := %!usages_flat{$name};
unless @usages {
@usages := [];
%!usages_flat{$var.name} := @usages;
%!usages_flat{$name} := @usages;
}
nqp::push(@usages, $var);
}

method poison_lowering() { $!poisoned := 1; }

method get_decls() { %!decls }

method get_usages_flat() { %!usages_flat }

method get_usages_inner() { %!usages_inner }

method is_flattenable() {
for %!decls {
return 0 if $_.value.scope eq 'lexical';
return 0 if $_.value.decl eq 'param';
}
1
}

method incorporate_inner($vars_info, $flattened) {
# We'll exclude anything that the inner or flattened thing has as
# a declaration, since those are its own.
my %decls := $vars_info.get_decls;

# Inner ones always go into our inners set.
add_to_set(%!usages_inner, $vars_info.get_usages_inner, %decls);

# Flat ones depend on if we flattened this block into ourself.
add_to_set($flattened ?? %!usages_flat !! %!usages_inner,
$vars_info.get_usages_flat, %decls);

sub add_to_set(%set, %to_add, %exclude) {
for %to_add {
my $name := $_.key;
next if nqp::existskey(%exclude, $name);
my @existing := %set{$name};
if @existing {
for $_.value { nqp::push(@existing, $_) }
#nqp::splice(@existing, $_.value, 0, 0);
}
else {
%set{$name} := $_.value;
}
}
}
}

method lexicals_to_locals() {
return 0 if $!poisoned;
for %!decls {
# We're looking for lexical var or param decls.
my $qast := $_.value;
my str $scope := $qast.scope;
next unless $scope eq 'lexical';
my str $decl := $qast.decl;
next unless $decl eq 'param' || $decl eq 'var';

# Consider name. Can't lower if it's used by any nested blocks.
my str $name := $_.key;
unless nqp::existskey(%!usages_inner, $name) {
# Lowerable if it's a normal variable.
next if nqp::chars($name) < 2;
my str $sigil := nqp::substr($name, 0, 1);
next unless $sigil eq '$' || $sigil eq '@' || $sigil eq '%';
next unless nqp::iscclass(nqp::const::CCLASS_ALPHABETIC, $name, 1);

# Seems good; lower it.
my $new_name := $qast.unique('__lowered_lex');
$qast.scope('local');
$qast.name($new_name);
if %!usages_flat{$name} {
for %!usages_flat{$name} {
$_.scope('local');
$_.name($new_name);
}
}
}
}
}
}

has @!block_stack;
Expand All @@ -42,11 +123,39 @@ class NQP::Optimizer {
}

method visit_block($block) {
# Push block and a new block vars tracking block.
@!block_stack.push($block);
@!block_var_stack.push(BlockVars.new);

# Visit all children, which includes nested blocks.
self.visit_children($block);

# Methods with late-bound names poison lowering.
if nqp::substr($block.name, 0, 12) eq '!!LATENAME!!' {
self.poison_lowering();
}

# Pop the block and the vars info.
@!block_stack.pop();
@!block_var_stack.pop();
my $vars_info := @!block_var_stack.pop();

# Lower any declarations we can.
$vars_info.lexicals_to_locals();

# If the block has no lexical declarations remaining, and it was an
# immediate block, then flatten it in.
my int $flattened := 0;
if $block.blocktype eq 'immediate' || $block.blocktype eq 'immediate_static' {
if $vars_info.is_flattenable {
my @innards := $block.list;
$block := QAST::Stmts.new( |@innards );
$flattened := 1;
}
}

# Incorporate this block's info into outer block's info.
@!block_var_stack[nqp::elems(@!block_var_stack) - 1].incorporate_inner($vars_info, $flattened);

$block;
}

Expand All @@ -59,8 +168,22 @@ class NQP::Optimizer {
return self.visit_handle($op);
}

# Visit children first.
self.visit_children($op);
# A for loop must have its block treated as a declaration; besides
# that, visit children as normal.
if $opname eq 'for' {
my $orig := $op[1].blocktype;
$op[1].blocktype('declaration');
self.visit_children($op);
$op[1].blocktype($orig);
}
else {
self.visit_children($op);
}

# nqp::ctx and nqp::curlexpad capture the current context and so poisons lowering
if $opname eq 'ctx' || $opname eq 'curlexpad' {
self.poison_lowering();
}

# Consider numeric ops we can simplify.
my $typeinfo := nqp::chars($opname) > 2
Expand Down Expand Up @@ -147,12 +270,17 @@ class NQP::Optimizer {
}

method visit_var($var) {
my int $top := nqp::elems(@!block_var_stack) - 1;
if $var.decl {
@!block_var_stack[$top].add_decl($var);
}
else {
@!block_var_stack[$top].add_usage($var);
my str $scope := $var.scope;
if $scope eq 'positional' || $scope eq 'associative' {
self.visit_children($var);
} else {
my int $top := nqp::elems(@!block_var_stack) - 1;
if $var.decl {
@!block_var_stack[$top].add_decl($var);
}
else {
@!block_var_stack[$top].add_usage($var);
}
}
}

Expand All @@ -171,6 +299,7 @@ class NQP::Optimizer {
} elsif nqp::istype($visit, QAST::Want) {
self.visit_children($visit, :skip_selectors)
} elsif nqp::istype($visit, QAST::Regex) {
self.poison_lowering();
QRegex::Optimizer.new().optimize($visit, @!block_stack[+@!block_stack - 1], |%!adverbs);
} else {
self.visit_children($visit);
Expand Down Expand Up @@ -202,4 +331,10 @@ class NQP::Optimizer {
nqp::die("No compile-time value for $name");
}
}

method poison_lowering() {
for @!block_var_stack {
$_.poison_lowering();
}
}
}

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