Escape_context::Escape_context(Gogo* gogo, bool recursive)
: gogo_(gogo), current_function_(NULL), recursive_(recursive),
- sink_(Node::make_node(Named_object::make_sink())), loop_depth_(0)
+ sink_(Node::make_node(Named_object::make_sink())), loop_depth_(0),
+ flood_id_(0), pdepth_(0)
{
// The sink always escapes to heap and strictly lives outside of the
// current function i.e. loop_depth == -1.
context->set_loop_depth(save_depth);
}
+class Escape_analysis_flood
+{
+ public:
+ Escape_analysis_flood(Escape_context* context)
+ : context_(context)
+ { }
+
+ // Use the escape information in dst to update the escape information in src
+ // and src's upstream.
+ void
+ flood(Level, Node* dst, Node* src, int);
+
+ private:
+ // The escape context for the group of functions being flooded.
+ Escape_context* context_;
+};
+
+// Whenever we hit a dereference node, the level goes up by one, and whenever
+// we hit an address-of, the level goes down by one. as long as we're on a
+// level > 0 finding an address-of just means we're following the upstream
+// of a dereference, so this address doesn't leak (yet).
+// If level == 0, it means the /value/ of this node can reach the root of this
+// flood so if this node is an address-of, its argument should be marked as
+// escaping iff its current function and loop depth are different from the
+// flood's root.
+// Once an object has been moved to the heap, all of its upstream should be
+// considered escaping to the global scope.
+// This is an implementation of gc/esc.go:escwalkBody.
+
+void
+Escape_analysis_flood::flood(Level level, Node* dst, Node* src,
+ int extra_loop_depth)
+{
+ // No need to flood src if it is a literal.
+ if (src->expr() != NULL)
+ {
+ switch (src->expr()->classification())
+ {
+ case Expression::EXPRESSION_BOOLEAN:
+ case Expression::EXPRESSION_STRING:
+ case Expression::EXPRESSION_INTEGER:
+ case Expression::EXPRESSION_FLOAT:
+ case Expression::EXPRESSION_COMPLEX:
+ case Expression::EXPRESSION_NIL:
+ case Expression::EXPRESSION_IOTA:
+ return;
+
+ default:
+ break;
+ }
+ }
+
+ Node::Escape_state* src_state = src->state(this->context_, NULL);
+ if (src_state->flood_id == this->context_->flood_id())
+ {
+ // Esclevels are vectors, do not compare as integers,
+ // and must use "min" of old and new to guarantee
+ // convergence.
+ level = level.min(src_state->level);
+ if (level == src_state->level)
+ {
+ // Have we been here already with an extraloopdepth,
+ // or is the extraloopdepth provided no improvement on
+ // what's already been seen?
+ if (src_state->max_extra_loop_depth >= extra_loop_depth
+ || src_state->loop_depth >= extra_loop_depth)
+ return;
+ src_state->max_extra_loop_depth = extra_loop_depth;
+ }
+ }
+ else
+ src_state->max_extra_loop_depth = -1;
+
+ src_state->flood_id = this->context_->flood_id();
+ src_state->level = level;
+ int mod_loop_depth = std::max(extra_loop_depth, src_state->loop_depth);
+
+ this->context_->increase_pdepth();
+
+ // Input parameter flowing into output parameter?
+ Named_object* src_no = NULL;
+ if (src->expr() != NULL && src->expr()->var_expression() != NULL)
+ src_no = src->expr()->var_expression()->named_object();
+ else
+ src_no = src->object();
+ bool src_is_param = (src_no != NULL
+ && src_no->is_variable()
+ && src_no->var_value()->is_parameter());
+
+ Named_object* dst_no = NULL;
+ if (dst->expr() != NULL && dst->expr()->var_expression() != NULL)
+ dst_no = dst->expr()->var_expression()->named_object();
+ else
+ dst_no = dst->object();
+ bool dst_is_result = dst_no != NULL && dst_no->is_result_variable();
+
+ if (src_is_param
+ && dst_is_result
+ && (src->encoding() & ESCAPE_MASK) < int(Node::ESCAPE_SCOPE)
+ && dst->encoding() != Node::ESCAPE_HEAP)
+ {
+ // This case handles:
+ // 1. return in
+ // 2. return &in
+ // 3. tmp := in; return &tmp
+ // 4. return *in
+ if ((src->encoding() & ESCAPE_MASK) != Node::ESCAPE_RETURN)
+ {
+ int enc =
+ Node::ESCAPE_RETURN | (src->encoding() & ESCAPE_CONTENT_ESCAPES);
+ src->set_encoding(enc);
+ }
+
+ int enc = Node::note_inout_flows(src->encoding(),
+ dst_no->result_var_value()->index(),
+ level);
+ src->set_encoding(enc);
+
+ // In gc/esc.go:escwalkBody, this is a goto to the label for recursively
+ // flooding the connection graph. Inlined here for convenience.
+ level = level.copy();
+ for (std::set<Node*>::const_iterator p = src_state->flows.begin();
+ p != src_state->flows.end();
+ ++p)
+ this->flood(level, dst, *p, extra_loop_depth);
+ return;
+ }
+
+ // If parameter content escape to heap, set ESCAPE_CONTENT_ESCAPES.
+ // Note minor confusion around escape from pointer-to-struct vs
+ // escape from struct.
+ if (src_is_param
+ && dst->encoding() == Node::ESCAPE_HEAP
+ && (src->encoding() & ESCAPE_MASK) < int(Node::ESCAPE_SCOPE)
+ && level.value() > 0)
+ {
+ int enc =
+ Node::max_encoding((src->encoding() | ESCAPE_CONTENT_ESCAPES),
+ Node::ESCAPE_NONE);
+ src->set_encoding(enc);
+ }
+
+ // A src object leaks if its value or address is assigned to a dst object
+ // in a different scope (at a different loop depth).
+ Node::Escape_state* dst_state = dst->state(this->context_, NULL);
+ bool src_leaks = (level.value() <= 0
+ && level.suffix_value() <= 0
+ && dst_state->loop_depth < mod_loop_depth);
+
+ if (src_is_param
+ && (src_leaks || dst_state->loop_depth < 0)
+ && (src->encoding() & ESCAPE_MASK) < int(Node::ESCAPE_SCOPE))
+ {
+ if (level.suffix_value() > 0)
+ {
+ int enc =
+ Node::max_encoding((src->encoding() | ESCAPE_CONTENT_ESCAPES),
+ Node::ESCAPE_NONE);
+ src->set_encoding(enc);
+ }
+ else
+ {
+ src->set_encoding(Node::ESCAPE_SCOPE);
+ }
+ }
+ else if (src->expr() != NULL)
+ {
+ Expression* e = src->expr();
+ if (e->enclosed_var_expression() != NULL)
+ {
+ Node* enclosed_node =
+ Node::make_node(e->enclosed_var_expression()->variable());
+ this->flood(level, dst, enclosed_node, -1);
+ }
+ else if (e->heap_expression() != NULL
+ || (e->unary_expression() != NULL
+ && e->unary_expression()->op() == OPERATOR_AND))
+ {
+ // Pointer literals and address-of expressions.
+ Expression* underlying;
+ if (e->heap_expression())
+ underlying = e->heap_expression()->expr();
+ else
+ underlying = e->unary_expression()->operand();
+ Node* underlying_node = Node::make_node(underlying);
+
+ // If the address leaks, the underyling object must be moved
+ // to the heap.
+ underlying->address_taken(src_leaks);
+ if (src_leaks)
+ {
+ src->set_encoding(Node::ESCAPE_HEAP);
+ this->flood(level.decrease(), dst,
+ underlying_node, mod_loop_depth);
+ extra_loop_depth = mod_loop_depth;
+ }
+ else
+ {
+ // Decrease the level each time we take the address of the object.
+ this->flood(level.decrease(), dst, underlying_node, -1);
+ }
+ }
+ else if (e->slice_literal() != NULL)
+ {
+ Slice_construction_expression* slice = e->slice_literal();
+ if (slice->vals() != NULL)
+ {
+ for (Expression_list::const_iterator p = slice->vals()->begin();
+ p != slice->vals()->end();
+ ++p)
+ {
+ if ((*p) != NULL)
+ this->flood(level.decrease(), dst, Node::make_node(*p), -1);
+ }
+ }
+ if (src_leaks)
+ {
+ src->set_encoding(Node::ESCAPE_HEAP);
+ extra_loop_depth = mod_loop_depth;
+ }
+ }
+ else if (e->call_expression() != NULL)
+ {
+ Call_expression* call = e->call_expression();
+ if (call->fn()->func_expression() != NULL)
+ {
+ Func_expression* func = call->fn()->func_expression();
+ if (func->is_runtime_function())
+ {
+ switch (func->runtime_code())
+ {
+ case Runtime::APPEND:
+ {
+ // Propagate escape information to appendee.
+ Expression* appendee = call->args()->front();
+ this->flood(level, dst, Node::make_node(appendee), -1);
+ }
+ break;
+
+ case Runtime::MAKECHAN:
+ case Runtime::MAKECHANBIG:
+ case Runtime::MAKEMAP:
+ case Runtime::MAKEMAPBIG:
+ case Runtime::MAKESLICE1:
+ case Runtime::MAKESLICE2:
+ case Runtime::MAKESLICE1BIG:
+ case Runtime::MAKESLICE2BIG:
+ case Runtime::BYTE_ARRAY_TO_STRING:
+ case Runtime::INT_ARRAY_TO_STRING:
+ case Runtime::STRING_TO_BYTE_ARRAY:
+ case Runtime::STRING_TO_INT_ARRAY:
+ case Runtime::STRING_PLUS:
+ case Runtime::CONSTRUCT_MAP:
+ case Runtime::INT_TO_STRING:
+ case Runtime::CONVERT_INTERFACE:
+ // All runtime calls that involve allocation of memory
+ // except new. Runtime::NEW gets lowered into an
+ // allocation expression.
+ if (src_leaks)
+ {
+ src->set_encoding(Node::ESCAPE_HEAP);
+ extra_loop_depth = mod_loop_depth;
+ }
+ break;
+
+ default:
+ break;
+ }
+ }
+ else if (src_leaks
+ && (func->closure() != NULL
+ || func->bound_method_expression() != NULL))
+ {
+ // A closure or bound method; we lost track of actual function
+ // so if this leaks, this call must be done on the heap.
+ src->set_encoding(Node::ESCAPE_HEAP);
+ }
+ }
+ }
+ else if (e->allocation_expression() != NULL && src_leaks)
+ {
+ // Calls to Runtime::NEW get lowered into an allocation expression.
+ src->set_encoding(Node::ESCAPE_HEAP);
+ }
+ else if ((e->field_reference_expression() != NULL
+ && e->field_reference_expression()->expr()->unary_expression() == NULL)
+ || e->type_guard_expression() != NULL
+ || (e->array_index_expression() != NULL
+ && e->type()->is_slice_type())
+ || (e->string_index_expression() != NULL
+ && e->type()->is_slice_type()))
+ {
+ Expression* underlying;
+ if (e->field_reference_expression() != NULL)
+ underlying = e->field_reference_expression()->expr();
+ else if (e->type_guard_expression() != NULL)
+ underlying = e->type_guard_expression()->expr();
+ else if (e->array_index_expression() != NULL)
+ underlying = e->array_index_expression()->array();
+ else
+ underlying = e->string_index_expression()->string();
+
+ Node* underlying_node = Node::make_node(underlying);
+ this->flood(level, dst, underlying_node, -1);
+ }
+ else if ((e->field_reference_expression() != NULL
+ && e->field_reference_expression()->expr()->unary_expression() != NULL)
+ || e->array_index_expression() != NULL
+ || e->map_index_expression() != NULL
+ || (e->unary_expression() != NULL
+ && e->unary_expression()->op() == OPERATOR_MULT))
+ {
+ Expression* underlying;
+ if (e->field_reference_expression() != NULL)
+ {
+ underlying = e->field_reference_expression()->expr();
+ underlying = underlying->unary_expression()->operand();
+ }
+ else if (e->array_index_expression() != NULL)
+ {
+ underlying = e->array_index_expression()->array();
+ if (!underlying->type()->is_slice_type())
+ {
+ Node* underlying_node = Node::make_node(underlying);
+ this->flood(level, dst, underlying_node, 1);
+ }
+ }
+ else if (e->map_index_expression() != NULL)
+ underlying = e->map_index_expression()->map();
+ else
+ underlying = e->unary_expression()->operand();
+
+ // Increase the level for a dereference.
+ Node* underlying_node = Node::make_node(underlying);
+ this->flood(level.increase(), dst, underlying_node, -1);
+ }
+
+ // TODO(cmang): Add case for Issue #10466.
+ }
+
+ level = level.copy();
+ for (std::set<Node*>::const_iterator p = src_state->flows.begin();
+ p != src_state->flows.end();
+ ++p)
+ this->flood(level, dst, *p, extra_loop_depth);
+
+ this->context_->decrease_pdepth();
+}
+
// Propagate escape information across the nodes modeled in this Analysis_set.
+// This is an implementation of gc/esc.go:escflood.
void
-Gogo::propagate_escape(Escape_context*, Node*)
+Gogo::propagate_escape(Escape_context* context, Node* dst)
{
- // TODO(cmang): Do a breadth-first traversal of a node's upstream, adjusting
- // the Level appropriately.
+ Node::Escape_state* state = dst->state(context, NULL);
+ Escape_analysis_flood eaf(context);
+ for (std::set<Node*>::const_iterator p = state->flows.begin();
+ p != state->flows.end();
+ ++p)
+ {
+ context->increase_flood_id();
+ eaf.flood(Level::From(0), dst, *p, -1);
+ }
}
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