Shader/SPIRV: Fix double termination of blocks when branching

Which could happen when using OpKill (discard) for example

src/Nazara/Shader/SpirvAstVisitor.cpp

@@ -376,7 +376,8 @@ namespace Nz
 
 		SpirvBlock mergeBlock(m_writer);
 
-		previousContentBlock.Append(SpirvOp::OpBranch, mergeBlock.GetLabelId()); //< FIXME: Shouldn't terminate twice
+		if (!previousContentBlock.IsTerminated())
+			previousContentBlock.Append(SpirvOp::OpBranch, mergeBlock.GetLabelId());
 
 		m_functionBlocks.back().Append(SpirvOp::OpSelectionMerge, mergeBlock.GetLabelId(), SpirvSelectionControl::None);
 
@@ -397,7 +398,8 @@ namespace Nz
 
 			statement.statement->Visit(*this);
 
-			previousContentBlock.Append(SpirvOp::OpBranch, mergeBlock.GetLabelId()); //< FIXME: Shouldn't terminate twice
+			if (!previousContentBlock.IsTerminated())
+				previousContentBlock.Append(SpirvOp::OpBranch, mergeBlock.GetLabelId());
 		}
 
 		if (node.elseStatement)
@@ -408,7 +410,8 @@ namespace Nz
 
 			node.elseStatement->Visit(*this);
 
-			elseBlock.Append(SpirvOp::OpBranch, mergeBlock.GetLabelId()); //< FIXME: Shouldn't terminate twice
+			if (!elseBlock.IsTerminated())
+				elseBlock.Append(SpirvOp::OpBranch, mergeBlock.GetLabelId());
 
 			m_functionBlocks.back().Append(SpirvOp::OpBranchConditional, previousConditionId, previousContentBlock.GetLabelId(), elseBlock.GetLabelId());
 			m_functionBlocks.emplace_back(std::move(previousContentBlock));

tests/Engine/Shader/Branch.cpp

@@ -8,7 +8,9 @@
 
 TEST_CASE("branching", "[Shader]")
 {
-	std::string_view nzslSource = R"(
+	WHEN("using a simple branch")
+	{
+		std::string_view nzslSource = R"(
 struct inputStruct
 {
 	value: f32
@@ -30,9 +32,9 @@ fn main()
 }
 )";
 
-	Nz::ShaderAst::StatementPtr shader = Nz::ShaderLang::Parse(nzslSource);
+		Nz::ShaderAst::StatementPtr shader = Nz::ShaderLang::Parse(nzslSource);
 
-	ExpectGLSL(*shader, R"(
+		ExpectGLSL(*shader, R"(
 void main()
 {
 	float value;
@@ -48,7 +50,7 @@ void main()
 }
 )");
 
-	ExpectNZSL(*shader, R"(
+		ExpectNZSL(*shader, R"(
 [entry(frag)]
 fn main()
 {
@@ -65,7 +67,7 @@ fn main()
 }
 )");
 
-	ExpectSpirV(*shader, R"(
+		ExpectSpirV(*shader, R"(
 OpFunction
 OpLabel
 OpVariable
@@ -83,4 +85,66 @@ OpBranch
 OpLabel
 OpReturn
 OpFunctionEnd)");
+	}
+
+	WHEN("discarding in a branch")
+	{
+		std::string_view nzslSource = R"(
+struct inputStruct
+{
+	value: f32
+}
+
+external
+{
+	[set(0), binding(0)] data: uniform<inputStruct>
+}
+
+[entry(frag)]
+fn main()
+{
+	if (data.value > 0.0)
+		discard;
+}
+)";
+
+		Nz::ShaderAst::StatementPtr shader = Nz::ShaderLang::Parse(nzslSource);
+
+		ExpectGLSL(*shader, R"(
+void main()
+{
+	if (data.value > (0.000000))
+	{
+		discard;
+	}
+	
+}
+)");
+
+		ExpectNZSL(*shader, R"(
+[entry(frag)]
+fn main()
+{
+	if (data.value > (0.000000))
+	{
+		discard;
+	}
+	
+}
+)");
+
+		ExpectSpirV(*shader, R"(
+OpFunction
+OpLabel
+OpAccessChain
+OpLoad
+OpFOrdGreaterThanEqual
+OpSelectionMerge
+OpBranchConditional
+OpLabel
+OpKill
+OpLabel
+OpReturn
+OpFunctionEnd)");
+	}
 }

tests/Engine/Shader/ShaderUtils.cpp

@@ -137,8 +137,8 @@ void ExpectGLSL(Nz::ShaderAst::Statement& shader, std::string_view expectedOutpu
 
 		WHEN("Validating full GLSL code (using glslang)")
 		{
-			glslang::TShader shader(EShLangVertex);
+			glslang::TShader shader(EShLangFragment);
-			shader.setEnvInput(glslang::EShSourceGlsl, EShLangVertex, glslang::EShClientOpenGL, 300);
+			shader.setEnvInput(glslang::EShSourceGlsl, EShLangFragment, glslang::EShClientOpenGL, 300);
 			shader.setEnvClient(glslang::EShClientOpenGL, glslang::EShTargetOpenGL_450);
 			shader.setEnvTarget(glslang::EShTargetNone, static_cast<glslang::EShTargetLanguageVersion>(0));
 			shader.setEntryPoint("main");