From c1b42fd479c5ca4cbab258ee0fa5c7cac319f928 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 2 Apr 2021 00:26:37 +0300
Subject: [PATCH] Make constant id range configurable and avoid duplicates

GlslangValidator apparently only allows IDs up to 2047.  I've yet to find
out if there's a limit in SPIR-V itself.
---
 source/glsl/compiler.cpp |  3 +--
 source/glsl/features.cpp |  3 ++-
 source/glsl/features.h   |  1 +
 source/glsl/generate.cpp | 27 ++++++++++++++++++++++++---
 source/glsl/generate.h   |  6 +++++-
 5 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/source/glsl/compiler.cpp b/source/glsl/compiler.cpp
index fab05473..5ff003e7 100644
--- a/source/glsl/compiler.cpp
+++ b/source/glsl/compiler.cpp
@@ -80,6 +80,7 @@ void Compiler::compile(Mode mode)
 {
 	for(list<Stage>::iterator i=module->stages.begin(); i!=module->stages.end(); ++i)
 		generate(*i);
+	ConstantIdAssigner().apply(*module, features);
 
 	bool valid = true;
 	for(list<Stage>::iterator i=module->stages.begin(); i!=module->stages.end(); ++i)
@@ -267,8 +268,6 @@ void Compiler::generate(Stage &stage)
 	variables through interfaces. */
 	InterfaceGenerator().apply(stage);
 	resolve(stage, RESOLVE_BLOCKS|RESOLVE_TYPES|RESOLVE_VARIABLES);
-
-	ConstantIdAssigner().apply(stage);
 }
 
 template<typename T>
diff --git a/source/glsl/features.cpp b/source/glsl/features.cpp
index 11b6c942..dab230d3 100644
--- a/source/glsl/features.cpp
+++ b/source/glsl/features.cpp
@@ -15,7 +15,8 @@ Features::Features():
 	arb_gpu_shader5(false),
 	arb_uniform_buffer_object(false),
 	ext_gpu_shader4(false),
-	ext_texture_array(false)
+	ext_texture_array(false),
+	max_constant_id(0x7FFFFFFF)
 { }
 
 Features Features::from_context()
diff --git a/source/glsl/features.h b/source/glsl/features.h
index 8d32f8be..b65a61e2 100644
--- a/source/glsl/features.h
+++ b/source/glsl/features.h
@@ -16,6 +16,7 @@ struct Features
 	bool arb_uniform_buffer_object;
 	bool ext_gpu_shader4;
 	bool ext_texture_array;
+	unsigned max_constant_id;
 
 	Features();
 
diff --git a/source/glsl/generate.cpp b/source/glsl/generate.cpp
index f345670b..92d172c5 100644
--- a/source/glsl/generate.cpp
+++ b/source/glsl/generate.cpp
@@ -8,9 +8,28 @@ namespace Msp {
 namespace GL {
 namespace SL {
 
-void ConstantIdAssigner::apply(Stage &stage)
+void ConstantIdAssigner::apply(Module &module, const Features &features)
 {
-	stage.content.visit(*this);
+	for(list<Stage>::iterator i=module.stages.begin(); i!=module.stages.end(); ++i)
+		i->content.visit(*this);
+
+	unsigned max_id = features.max_constant_id;
+	for(vector<VariableDeclaration *>::iterator i=auto_constants.begin(); i!=auto_constants.end(); ++i)
+	{
+		unsigned id = hash32((*i)->name)%(max_id+1);
+		while(used_ids.count(id))
+			++id;
+
+		vector<Layout::Qualifier> &qualifiers = (*i)->layout->qualifiers;
+		for(vector<Layout::Qualifier>::iterator j=qualifiers.begin(); j!=qualifiers.end(); ++j)
+			if(j->name=="constant_id")
+			{
+				j->value = id;
+				break;
+			}
+
+		used_ids.insert(id);
+	}
 }
 
 void ConstantIdAssigner::visit(VariableDeclaration &var)
@@ -22,7 +41,9 @@ void ConstantIdAssigner::visit(VariableDeclaration &var)
 			if(i->name=="constant_id" && i->has_value)
 			{
 				if(i->value==-1)
-					i->value = hash32(var.name)&0x7FFFFFFF;
+					auto_constants.push_back(&var);
+				else
+					used_ids.insert(i->value);
 				break;
 			}
 	}
diff --git a/source/glsl/generate.h b/source/glsl/generate.h
index b2cfadc4..eb7d488a 100644
--- a/source/glsl/generate.h
+++ b/source/glsl/generate.h
@@ -14,8 +14,12 @@ namespace SL {
 /** Assigns IDs to specialization constants with an automatic ID. */
 class ConstantIdAssigner: private TraversingVisitor
 {
+private:
+	std::set<unsigned> used_ids;
+	std::vector<VariableDeclaration *> auto_constants;
+
 public:
-	void apply(Stage &);
+	void apply(Module &, const Features &);
 
 private:
 	virtual void visit(VariableDeclaration &);
-- 
2.43.0