Add fast-path to GSUB to check coverage
Shaves a good 10% off DejaVu Sans with simple Latin text for me.
Now, DejaVu is very ChainContext-intensive, but it's also a very
popular font!
diff --git a/src/hb-ot-layout-gsub-table.hh b/src/hb-ot-layout-gsub-table.hh
index 6a4199d..caaaa85 100644
--- a/src/hb-ot-layout-gsub-table.hh
+++ b/src/hb-ot-layout-gsub-table.hh
@@ -968,6 +968,17 @@
inline bool apply (hb_apply_context_t *c, unsigned int lookup_type) const
{
TRACE_APPLY ();
+ if (likely (lookup_type < Context) ||
+ (hb_in_range<unsigned int> (lookup_type, Context, ChainContext) &&
+ hb_in_range<unsigned int> (u.header.sub_format, 1, 2)))
+ {
+ /* Fast path, for most that have coverage in the same place.
+ * Note that ReverseChainSingle can also go through this but
+ * it's not worth the effort. */
+ hb_codepoint_t glyph_id = c->buffer->cur().codepoint;
+ unsigned int index = (this+u.header.coverage) (glyph_id);
+ if (likely (index == NOT_COVERED)) return TRACE_RETURN (false);
+ }
switch (lookup_type) {
case Single: return TRACE_RETURN (u.single.apply (c));
case Multiple: return TRACE_RETURN (u.multiple.apply (c));
@@ -998,7 +1009,10 @@
private:
union {
- USHORT sub_format;
+ struct {
+ USHORT sub_format;
+ OffsetTo<Coverage> coverage;
+ } header;
SingleSubst single;
MultipleSubst multiple;
AlternateSubst alternate;
@@ -1009,7 +1023,7 @@
ReverseChainSingleSubst reverseChainContextSingle;
} u;
public:
- DEFINE_SIZE_UNION (2, sub_format);
+ DEFINE_SIZE_UNION (2, header.sub_format);
};
