From 05d8360ceef28e0b36e96127e04a82dd77a5c433 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 10 Mar 2021 12:12:26 +0200
Subject: [PATCH] Make ConstantConditionEliminator less trigger-happy

Since I removed the variable value tracking in 1cd0ea7 it started
optimizing conditions on specialization constants, even when they
had not been specialized yet.
---
 source/glsl/optimize.cpp                      | 17 +++---
 tests/glsl/keep_spec_constants_in_module.glsl | 59 +++++++++++++++++++
 tests/glsl/specialization_constants.glsl      | 50 ++++++++++++++++
 3 files changed, 117 insertions(+), 9 deletions(-)
 create mode 100644 tests/glsl/keep_spec_constants_in_module.glsl
 create mode 100644 tests/glsl/specialization_constants.glsl

diff --git a/source/glsl/optimize.cpp b/source/glsl/optimize.cpp
index 500c8417..87a57eb7 100644
--- a/source/glsl/optimize.cpp
+++ b/source/glsl/optimize.cpp
@@ -523,15 +523,14 @@ void ConstantConditionEliminator::visit(Block &block)
 
 void ConstantConditionEliminator::visit(Conditional &cond)
 {
-	ExpressionEvaluator eval;
-	cond.condition->visit(eval);
-	if(eval.is_result_valid())
-	{
-		Block &block = (eval.get_result() ? cond.body : cond.else_body);
-		current_block->body.splice(insert_point, block.body);
-		nodes_to_remove.insert(&cond);
-		return;
-	}
+	if(Literal *literal = dynamic_cast<Literal *>(cond.condition.get()))
+		if(literal->value.check_type<bool>())
+		{
+			Block &block = (literal->value.value<bool>() ? cond.body : cond.else_body);
+			current_block->body.splice(insert_point, block.body);
+			nodes_to_remove.insert(&cond);
+			return;
+		}
 
 	TraversingVisitor::visit(cond);
 }
diff --git a/tests/glsl/keep_spec_constants_in_module.glsl b/tests/glsl/keep_spec_constants_in_module.glsl
new file mode 100644
index 00000000..a7feab17
--- /dev/null
+++ b/tests/glsl/keep_spec_constants_in_module.glsl
@@ -0,0 +1,59 @@
+layout(constant_id=0) const bool use_texture = false;
+layout(constant_id=1) const bool use_vertex_color = false;
+uniform sampler2D tex;
+uniform mat4 mvp;
+
+#pragma MSP stage(vertex)
+layout(location=0) in vec4 position;
+layout(location=1) in vec4 color;
+layout(location=2) in vec2 texcoord;
+void main()
+{
+	passthrough;
+	gl_Position = mvp*position;
+}
+
+#pragma MSP stage(fragment)
+layout(location=0) out vec4 frag_color;
+void main()
+{
+	frag_color = vec4(1.0);
+	if(use_texture)
+		frag_color *= texture(tex, texcoord);
+	if(use_vertex_color)
+		frag_color *= color;
+}
+
+// Compile mode: module
+
+/* Expected output: vertex
+uniform mat4 mvp;
+layout(location=0) in vec4 position;
+layout(location=1) in vec4 color;
+layout(location=2) in vec2 texcoord;
+out vec4 _vs_out_color;
+out vec2 _vs_out_texcoord;
+void main()
+{
+	_vs_out_color = color;
+	_vs_out_texcoord = texcoord;
+	gl_Position = mvp*position;
+}
+*/
+
+/* Expected output: fragment
+layout(constant_id=0) const bool use_texture = false;
+layout(constant_id=1) const bool use_vertex_color = false;
+uniform sampler2D tex;
+layout(location=0) out vec4 frag_color;
+in vec2 _vs_out_texcoord;
+in vec4 _vs_out_color;
+void main()
+{
+  frag_color = vec4(1.0);
+  if(use_texture)
+    frag_color *= texture(tex, _vs_out_texcoord);
+  if(use_vertex_color)
+    frag_color *= _vs_out_color;
+}
+*/
diff --git a/tests/glsl/specialization_constants.glsl b/tests/glsl/specialization_constants.glsl
new file mode 100644
index 00000000..b5666f2d
--- /dev/null
+++ b/tests/glsl/specialization_constants.glsl
@@ -0,0 +1,50 @@
+layout(constant_id=0) const bool use_texture = false;
+layout(constant_id=1) const bool use_vertex_color = false;
+uniform sampler2D tex;
+uniform mat4 mvp;
+
+#pragma MSP stage(vertex)
+layout(location=0) in vec4 position;
+layout(location=1) in vec4 color;
+layout(location=2) in vec2 texcoord;
+void main()
+{
+	passthrough;
+	gl_Position = mvp*position;
+}
+
+#pragma MSP stage(fragment)
+layout(location=0) out vec4 frag_color;
+void main()
+{
+	frag_color = vec4(1.0);
+	if(use_texture)
+		frag_color *= texture(tex, texcoord);
+	if(use_vertex_color)
+		frag_color *= color;
+}
+
+// Specialize: use_texture true
+
+/* Expected output: vertex
+uniform mat4 mvp;
+layout(location=0) in vec4 position;
+layout(location=2) in vec2 texcoord;
+out vec2 _vs_out_texcoord;
+void main()
+{
+	_vs_out_texcoord = texcoord;
+	gl_Position = mvp*position;
+}
+*/
+
+/* Expected output: fragment
+uniform sampler2D tex;
+layout(location=0) out vec4 frag_color;
+in vec2 _vs_out_texcoord;
+void main()
+{
+	frag_color = vec4(1.0);
+	frag_color *= texture(tex, _vs_out_texcoord);
+}
+*/
-- 
2.43.0