From 2e9d0beaafa8220d8a917749c8a12beaf4718729 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 7 Nov 2021 14:32:33 +0200
Subject: [PATCH] Disallow specialization constants in certain contexts

The initialization of a specialization constant must not use other
specialization constants.

Arrays sized by a specialization constant inside structures are broken
by design because member offsets in SPIR-V are required to be literals.
Changing the size through specialization would at best leave empty space
in the struct and at worst overlap other members.
---
 source/glsl/validate.cpp                    | 35 +++++++++++++++++----
 source/glsl/validate.h                      | 11 ++++++-
 tests/glsl/specialized_array_in_struct.glsl | 26 ++-------------
 3 files changed, 42 insertions(+), 30 deletions(-)

diff --git a/source/glsl/validate.cpp b/source/glsl/validate.cpp
index ec322f42..f12177db 100644
--- a/source/glsl/validate.cpp
+++ b/source/glsl/validate.cpp
@@ -1,5 +1,5 @@
-#include <algorithm>
 #include <cstring>
+#include <msp/core/algorithm.h>
 #include <msp/core/raii.h>
 #include <msp/strings/format.h>
 #include <msp/strings/utils.h>
@@ -497,8 +497,17 @@ void ReferenceValidator::visit(FunctionDeclaration &func)
 
 void ExpressionValidator::visit(VariableReference &var)
 {
-	if(var.declaration && constant_expression && !var.declaration->constant)
-		error(var, format("Reference to non-constant variable '%s' in a constant expression", var.name));
+	if(var.declaration && constant_expression)
+	{
+		if(!var.declaration->constant)
+			error(var, format("Reference to non-constant variable '%s' in a constant expression", var.name));
+		else if(var.declaration->layout && constant_expression==FIXED_CONSTANT)
+		{
+			auto i = find_member(var.declaration->layout->qualifiers, string("constant_id"), &Layout::Qualifier::name);
+			if(i!=var.declaration->layout->qualifiers.end())
+				error(var, format("Reference to specialization constant '%s' in a fixed constant expression", var.name));
+		}
+	}
 }
 
 void ExpressionValidator::visit(InterfaceBlockReference &iface)
@@ -524,7 +533,7 @@ void ExpressionValidator::visit(Swizzle &swizzle)
 		int flavour = -1;
 		for(unsigned i=0; i<swizzle.count; ++i)
 		{
-			unsigned component_flavour = (find(component_names, component_names+12, swizzle.component_group[i])-component_names)/4;
+			unsigned component_flavour = (std::find(component_names, component_names+12, swizzle.component_group[i])-component_names)/4;
 			if(flavour==-1)
 				flavour = component_flavour;
 			else if(flavour>=0 && component_flavour!=static_cast<unsigned>(flavour))
@@ -614,6 +623,12 @@ void ExpressionValidator::visit(TernaryExpression &ternary)
 	TraversingVisitor::visit(ternary);
 }
 
+void ExpressionValidator::visit(StructDeclaration &strct)
+{
+	SetFlag set_struct(in_struct);
+	TraversingVisitor::visit(strct);
+}
+
 void ExpressionValidator::visit(VariableDeclaration &var)
 {
 	if(var.init_expression && var.init_expression->type && var.type_declaration && var.init_expression->type!=var.type_declaration)
@@ -624,12 +639,20 @@ void ExpressionValidator::visit(VariableDeclaration &var)
 		var.layout->visit(*this);
 	if(var.init_expression)
 	{
-		SetFlag set_const(constant_expression, var.constant);
+		ConstantKind const_kind = (var.constant ? SPEC_CONSTANT : NOT_CONSTANT);
+		if(var.layout)
+		{
+			auto i = find_member(var.layout->qualifiers, string("constant_id"), &Layout::Qualifier::name);
+			if(i!=var.layout->qualifiers.end())
+				const_kind = FIXED_CONSTANT;
+		}
+
+		SetForScope<ConstantKind> set_const(constant_expression, const_kind);
 		TraversingVisitor::visit(var.init_expression);
 	}
 	if(var.array_size)
 	{
-		SetFlag set_const(constant_expression);
+		SetForScope<ConstantKind> set_const(constant_expression, (in_struct || !var.interface.empty() ? FIXED_CONSTANT : SPEC_CONSTANT));
 		TraversingVisitor::visit(var.array_size);
 	}
 }
diff --git a/source/glsl/validate.h b/source/glsl/validate.h
index 52ae136b..b47a9911 100644
--- a/source/glsl/validate.h
+++ b/source/glsl/validate.h
@@ -113,8 +113,16 @@ is indicated by a null result type. */
 class ExpressionValidator: private Validator
 {
 private:
+	enum ConstantKind
+	{
+		NOT_CONSTANT,
+		FIXED_CONSTANT,
+		SPEC_CONSTANT
+	};
+
 	FunctionDeclaration *current_function = 0;
-	bool constant_expression = false;
+	bool in_struct = false;
+	ConstantKind constant_expression = NOT_CONSTANT;
 
 public:
 	void apply(Stage &s) { stage = &s; s.content.visit(*this); }
@@ -127,6 +135,7 @@ private:
 	virtual void visit(BinaryExpression &);
 	virtual void visit(Assignment &);
 	virtual void visit(TernaryExpression &);
+	virtual void visit(StructDeclaration &);
 	virtual void visit(VariableDeclaration &);
 	virtual void visit(FunctionDeclaration &);
 	virtual void visit(Conditional &);
diff --git a/tests/glsl/specialized_array_in_struct.glsl b/tests/glsl/specialized_array_in_struct.glsl
index 4a6d9ab6..f82bd74e 100644
--- a/tests/glsl/specialized_array_in_struct.glsl
+++ b/tests/glsl/specialized_array_in_struct.glsl
@@ -24,27 +24,7 @@ void main()
 
 // Compile mode: module
 
-/* Expected output: vertex
-layout(location=0) in vec4 position;
-void main()
-{
-	gl_Position = position;
-}
-*/
-
-/* Expected output: fragment
-layout(constant_id=953017667) const int max_colors = 2;
-struct ColorInfo
-{
-	vec4 color;
-};
-layout(binding=23) uniform Colors
-{
-	ColorInfo colors[max_colors];
-};
-layout(location=0) out vec4 frag_color;
-void main()
-{
-	frag_color = colors[0].color;
-}
+/* Expected error:
+<test>:8: Reference to specialization constant 'max_colors' in a fixed constant expression
+<test>:8: Reference to specialization constant 'max_colors' in a fixed constant expression
 */
-- 
2.43.0