Merge pull request #898 from KhronosGroup/fix-897

GLSL: Fix some complex cases for loading arrays

1 files changed, 58 insertions, 0 deletions

diff --git a/spirv_glsl.cpp b/spirv_glsl.cpp
index e8260b1d..d04adae4 100644
--- a/spirv_glsl.cpp
+++ b/spirv_glsl.cpp
@@ -6909,6 +6909,11 @@ void CompilerGLSL::emit_instruction(const Instruction &instruction)
 		// We might need to bitcast in order to load from a builtin.
 		bitcast_from_builtin_load(ptr, expr, get<SPIRType>(result_type));
 
+		// We might be trying to load a gl_Position[N], where we should be
+		// doing float4[](gl_in[i].gl_Position, ...) instead.
+		// Similar workarounds are required for input arrays in tessellation.
+		unroll_array_from_complex_load(id, ptr, expr);
+
 		if (ptr_expression)
 			ptr_expression->need_transpose = old_need_transpose;
 
@@ -11041,6 +11046,59 @@ void CompilerGLSL::emit_array_copy(const string &lhs, uint32_t rhs_id)
 	statement(lhs, " = ", to_expression(rhs_id), ";");
 }
 
+void CompilerGLSL::unroll_array_from_complex_load(uint32_t target_id, uint32_t source_id, std::string &expr)
+{
+	if (!backend.force_gl_in_out_block)
+		return;
+	// This path is only relevant for GL backends.
+
+	auto *var = maybe_get<SPIRVariable>(source_id);
+	if (!var)
+		return;
+
+	if (var->storage != StorageClassInput)
+		return;
+
+	auto &type = get_variable_data_type(*var);
+	if (type.array.empty())
+		return;
+
+	auto builtin = BuiltIn(get_decoration(var->self, DecorationBuiltIn));
+	bool is_builtin = is_builtin_variable(*var) && (builtin == BuiltInPointSize || builtin == BuiltInPosition);
+	bool is_tess = is_tessellation_shader();
+
+	// Tessellation input arrays are special in that they are unsized, so we cannot directly copy from it.
+	// We must unroll the array load.
+	// For builtins, we couldn't catch this case normally,
+	// because this is resolved in the OpAccessChain in most cases.
+	// If we load the entire array, we have no choice but to unroll here.
+	if (is_builtin || is_tess)
+	{
+		auto new_expr = join("_", target_id, "_unrolled");
+		statement(variable_decl(type, new_expr, target_id), ";");
+		string array_expr;
+		if (type.array_size_literal.front())
+		{
+			array_expr = convert_to_string(type.array.front());
+			if (type.array.front() == 0)
+				SPIRV_CROSS_THROW("Cannot unroll an array copy from unsized array.");
+		}
+		else
+			array_expr = to_expression(type.array.front());
+
+		// The array size might be a specialization constant, so use a for-loop instead.
+		statement("for (int i = 0; i < int(", array_expr, "); i++)");
+		begin_scope();
+		if (is_builtin)
+			statement(new_expr, "[i] = gl_in[i].", expr, ";");
+		else
+			statement(new_expr, "[i] = ", expr, "[i];");
+		end_scope();
+
+		expr = move(new_expr);
+	}
+}
+
 void CompilerGLSL::bitcast_from_builtin_load(uint32_t source_id, std::string &expr,
                                              const spirv_cross::SPIRType &expr_type)
 {