From f7682c3c2e9f028cef6945ffbada66cff33585c0 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 17 Nov 2021 15:34:06 +0200
Subject: [PATCH] Avoid emitting duplicate specialization constants in SPIR-V

---
 source/glsl/generate.cpp |  1 +
 source/glsl/spirv.cpp    | 12 +++++++++++-
 source/glsl/spirv.h      |  1 +
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/source/glsl/generate.cpp b/source/glsl/generate.cpp
index 85c3009b..3175c6c9 100644
--- a/source/glsl/generate.cpp
+++ b/source/glsl/generate.cpp
@@ -32,6 +32,7 @@ void ConstantIdAssigner::apply(Module &module, const Features &features)
 			i->value = id;
 
 		used_ids.insert(id);
+		existing_constants[v->name] = id;
 	}
 }
 
diff --git a/source/glsl/spirv.cpp b/source/glsl/spirv.cpp
index 40e731fe..7f0d0b70 100644
--- a/source/glsl/spirv.cpp
+++ b/source/glsl/spirv.cpp
@@ -1591,6 +1591,12 @@ void SpirVGenerator::visit(VariableDeclaration &var)
 			throw internal_error("const variable without initializer");
 
 		int spec_id = get_layout_value(var.layout.get(), "constant_id");
+		Id *spec_var_id = (spec_id>=0 ? &declared_spec_ids[spec_id] : 0);
+		if(spec_id>=0 && *spec_var_id)
+		{
+			insert_unique(declared_ids, &var, Declaration(*spec_var_id, type_id));
+			return;
+		}
 
 		SetFlag set_const(constant_expression);
 		SetFlag set_spec(spec_constant, spec_id>=0);
@@ -1598,7 +1604,11 @@ void SpirVGenerator::visit(VariableDeclaration &var)
 		var.init_expression->visit(*this);
 		var_id = r_expression_result_id;
 		insert_unique(declared_ids, &var, Declaration(var_id, type_id));
-		writer.write_op_decorate(var_id, DECO_SPEC_ID, spec_id);
+		if(spec_id>=0)
+		{
+			writer.write_op_decorate(var_id, DECO_SPEC_ID, spec_id);
+			*spec_var_id = var_id;
+		}
 
 		/* It's unclear what should be done if a specialization constant is
 		initialized with anything other than a literal.  GLSL doesn't seem to
diff --git a/source/glsl/spirv.h b/source/glsl/spirv.h
index 6971e2a9..59c7b50b 100644
--- a/source/glsl/spirv.h
+++ b/source/glsl/spirv.h
@@ -79,6 +79,7 @@ private:
 	std::map<std::string, Id> imported_extension_ids;
 	std::map<Node *, Declaration> declared_ids;
 	std::map<std::string, Id> declared_uniform_ids;
+	std::map<unsigned, Id> declared_spec_ids;
 	std::map<TypeKey, Id> standard_type_ids;
 	std::map<Id, Id> image_type_ids;
 	std::map<TypeKey, Id> array_type_ids;
-- 
2.43.0