Make meta a hashmap.

A flat array was consuming way too much memory and was far too slow to
initialize properly with a very large ID bound (8 million IDs, showed up as #1 hotspot in perf).

Meta struct does not have to be in-order as we never iterate over it in
a meaningful way, so using a hashmap here is reasonable. Very few IDs
should need decorations or meta-data, so this should also be a quite
decent memory save.

For the pathological case, a 6x uplift was observed.

1 files changed, 82 insertions, 38 deletions

diff --git a/spirv_cross_parsed_ir.cpp b/spirv_cross_parsed_ir.cpp
index 6d80fcb3..82bc5611 100644
--- a/spirv_cross_parsed_ir.cpp
+++ b/spirv_cross_parsed_ir.cpp
@@ -26,7 +26,6 @@ namespace spirv_cross
 void ParsedIR::set_id_bounds(uint32_t bounds)
 {
 	ids.resize(bounds);
-	meta.resize(bounds);
 	block_meta.resize(bounds);
 }
 
@@ -66,19 +65,24 @@ static string ensure_valid_identifier(const string &name, bool member)
 
 const string &ParsedIR::get_name(uint32_t id) const
 {
-	return meta[id].decoration.alias;
+	auto *m = find_meta(id);
+	if (m)
+		return m->decoration.alias;
+	else
+		return empty_string;
 }
 
 const string &ParsedIR::get_member_name(uint32_t id, uint32_t index) const
 {
-	auto &m = meta[id];
-	if (index >= m.members.size())
+	auto *m = find_meta(id);
+	if (m)
 	{
-		static string empty;
-		return empty;
+		if (index >= m->members.size())
+			return empty_string;
+		return m->members[index].alias;
 	}
-
-	return m.members[index].alias;
+	else
+		return empty_string;
 }
 
 void ParsedIR::set_name(uint32_t id, const string &name)
@@ -274,7 +278,10 @@ Bitset ParsedIR::get_buffer_block_flags(const SPIRVariable &var) const
 	// Some flags like non-writable, non-readable are actually found
 	// as member decorations. If all members have a decoration set, propagate
 	// the decoration up as a regular variable decoration.
-	Bitset base_flags = meta[var.self].decoration.decoration_flags;
+	Bitset base_flags;
+	auto *m = find_meta(var.self);
+	if (m)
+		base_flags = m->decoration.decoration_flags;
 
 	if (type.member_types.empty())
 		return base_flags;
@@ -289,14 +296,15 @@ Bitset ParsedIR::get_buffer_block_flags(const SPIRVariable &var) const
 
 const Bitset &ParsedIR::get_member_decoration_bitset(uint32_t id, uint32_t index) const
 {
-	auto &m = meta[id];
-	if (index >= m.members.size())
+	auto *m = find_meta(id);
+	if (m)
 	{
-		static const Bitset cleared = {};
-		return cleared;
+		if (index >= m->members.size())
+			return cleared_bitset;
+		return m->members[index].decoration_flags;
 	}
-
-	return m.members[index].decoration_flags;
+	else
+		return cleared_bitset;
 }
 
 bool ParsedIR::has_decoration(uint32_t id, Decoration decoration) const
@@ -306,7 +314,11 @@ bool ParsedIR::has_decoration(uint32_t id, Decoration decoration) const
 
 uint32_t ParsedIR::get_decoration(uint32_t id, Decoration decoration) const
 {
-	auto &dec = meta[id].decoration;
+	auto *m = find_meta(id);
+	if (!m)
+		return 0;
+
+	auto &dec = m->decoration;
 	if (!dec.decoration_flags.get(decoration))
 		return 0;
 
@@ -343,11 +355,14 @@ uint32_t ParsedIR::get_decoration(uint32_t id, Decoration decoration) const
 
 const string &ParsedIR::get_decoration_string(uint32_t id, Decoration decoration) const
 {
-	auto &dec = meta[id].decoration;
-	static const string empty;
+	auto *m = find_meta(id);
+	if (!m)
+		return empty_string;
+
+	auto &dec = m->decoration;
 
 	if (!dec.decoration_flags.get(decoration))
-		return empty;
+		return empty_string;
 
 	switch (decoration)
 	{
@@ -355,7 +370,7 @@ const string &ParsedIR::get_decoration_string(uint32_t id, Decoration decoration
 		return dec.hlsl_semantic;
 
 	default:
-		return empty;
+		return empty_string;
 	}
 }
 
@@ -428,11 +443,14 @@ bool ParsedIR::has_member_decoration(uint32_t id, uint32_t index, Decoration dec
 
 uint32_t ParsedIR::get_member_decoration(uint32_t id, uint32_t index, Decoration decoration) const
 {
-	auto &m = meta[id];
-	if (index >= m.members.size())
+	auto *m = find_meta(id);
+	if (!m)
 		return 0;
 
-	auto &dec = m.members[index];
+	if (index >= m->members.size())
+		return 0;
+
+	auto &dec = m->members[index];
 	if (!dec.decoration_flags.get(decoration))
 		return 0;
 
@@ -459,8 +477,14 @@ uint32_t ParsedIR::get_member_decoration(uint32_t id, uint32_t index, Decoration
 
 const Bitset &ParsedIR::get_decoration_bitset(uint32_t id) const
 {
-	auto &dec = meta[id].decoration;
-	return dec.decoration_flags;
+	auto *m = find_meta(id);
+	if (m)
+	{
+		auto &dec = m->decoration;
+		return dec.decoration_flags;
+	}
+	else
+		return cleared_bitset;
 }
 
 void ParsedIR::set_member_decoration_string(uint32_t id, uint32_t index, Decoration decoration, const string &argument)
@@ -482,22 +506,25 @@ void ParsedIR::set_member_decoration_string(uint32_t id, uint32_t index, Decorat
 
 const string &ParsedIR::get_member_decoration_string(uint32_t id, uint32_t index, Decoration decoration) const
 {
-	static const string empty;
-	auto &m = meta[id];
-
-	if (!has_member_decoration(id, index, decoration))
-		return empty;
+	auto *m = find_meta(id);
+	if (m)
+	{
+		if (!has_member_decoration(id, index, decoration))
+			return empty_string;
 
-	auto &dec = m.members[index];
+		auto &dec = m->members[index];
 
-	switch (decoration)
-	{
-	case DecorationHlslSemanticGOOGLE:
-		return dec.hlsl_semantic;
+		switch (decoration)
+		{
+		case DecorationHlslSemanticGOOGLE:
+			return dec.hlsl_semantic;
 
-	default:
-		return empty;
+		default:
+			return empty_string;
+		}
 	}
+	else
+		return empty_string;
 }
 
 void ParsedIR::unset_member_decoration(uint32_t id, uint32_t index, Decoration decoration)
@@ -545,7 +572,6 @@ uint32_t ParsedIR::increase_bound_by(uint32_t incr_amount)
 	auto curr_bound = ids.size();
 	auto new_bound = curr_bound + incr_amount;
 	ids.resize(new_bound);
-	meta.resize(new_bound);
 	block_meta.resize(new_bound);
 	return uint32_t(curr_bound);
 }
@@ -601,4 +627,22 @@ void ParsedIR::add_typed_id(Types type, uint32_t id)
 	}
 }
 
+const Meta *ParsedIR::find_meta(uint32_t id) const
+{
+	auto itr = meta.find(id);
+	if (itr != end(meta))
+		return &itr->second;
+	else
+		return nullptr;
+}
+
+Meta *ParsedIR::find_meta(uint32_t id)
+{
+	auto itr = meta.find(id);
+	if (itr != end(meta))
+		return &itr->second;
+	else
+		return nullptr;
+}
+
 } // namespace spirv_cross