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[repacker] put each 32 bit subgraph into it's own packing space. 

Each subgraph pointed to by a 32 bit offset should be packed into it's own space. This adds a space property to vertices which affects the distance calculation. This effectively places the distances for all of the nodes of a 32 bit subgraph into a distinct range. Thus all of the nodes of the subgraph will be packed together.
This commit is contained in:
Garret Rieger 2021-09-08 16:08:48 -07:00
parent 543a3f9733
commit 58facaade1
2 changed files with 13 additions and 2 deletions
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12
src/hb-repacker.hh
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@ -40,6 +40,7 @@ struct graph_t
{
vertex_t () :
distance (0),
space (1),
incoming_edges (0),
start (0),
end (0),
@ -49,6 +50,7 @@ struct graph_t
hb_serialize_context_t::object_t obj;
int64_t distance;
int64_t space;
unsigned incoming_edges;
unsigned start;
unsigned end;
@ -336,6 +338,7 @@ struct graph_t
bool made_changes = false;
hb_set_t target_links;
unsigned root_index = root_idx ();
int64_t next_space = 1;
for (unsigned i = 0; i <= root_index; i++)
{
if (i == root_index && root_idx () > i)
@ -345,7 +348,12 @@ struct graph_t
for (auto& l : vertices_[i].obj.links)
{
if (l.width == 4 && !l.is_signed)
made_changes = isolate_subgraph (l.objidx) || made_changes;
{
isolate_subgraph (l.objidx);
vertices_[l.objidx].space = next_space++;
distance_invalid = true;
made_changes = true;
}
}
}
return made_changes;
@ -635,7 +643,7 @@ struct graph_t
const auto& child = vertices_[link.objidx].obj;
int64_t child_weight = child.tail - child.head +
((int64_t) 1 << (link.width * 8));
((int64_t) 1 << (link.width * 8)) * vertices_[link.objidx].space;
int64_t child_distance = next_distance + child_weight;
if (child_distance < vertices_[link.objidx].distance)

3
src/test-repacker.cc
View File

@ -520,6 +520,9 @@ static void test_resolve_overflows_via_isolation ()
free (out_buffer);
}
// TODO(grieger): test for recursively duplicated nodes during isolation.
// TODO(grieger): test that isolated subgraphs are packed tightly within the subgraph.
// TODO(garretrieger): update will_overflow tests to check the overflows array.
// TODO(garretrieger): add a test(s) using a real font.
// TODO(garretrieger): add tests for priority raising.