test framework for AVR codegen

[pointbazaar]

Currently, to write a test for the AVR backend, it is a rather manual process,
compared to x86-64 where it's possible to just test using the (filename.exitcode) file.

Example:

void test_gen_tac_mdirect_case_variable_addr() {

	status_test_codegen_tac("MDirect - variable Address");

	//we need an address here which is small enough
	//to fit into a register. 0xc7 is usable.
	for (uint16_t address = 0xc7; address < 0xcb; address++) {

		const int8_t value = 0x38;

		char snippet[200];
		sprintf(snippet, "fn main() -> int { int y = 3; int x = [y+%d, 1]; return x; }", address);

		vmcu_system_t* system = prepare_vmcu_system_from_code_snippet(snippet);

		//prepare a value in the location
		vmcu_system_write_data(system, address + 3, value);

		for (int i = 0; i < 40; i++) {
			vmcu_system_step(system);
		}

		//return value in r0
		int8_t actual = vmcu_system_read_gpr(system, 0);

		assert(value == actual);

		vmcu_system_dtor(system);
	}
}

But what's happening is very similar across most testcases

• compile some code snippet
• prepare some data in memory using vmcu_system_write_data(system, address, value);
• run it with vmcu_system for n cycles
• read some data in memory using vmcu_system_read_data(system, address);
• read some registers, mostry r0 and r1
• assert on the value in registers or in memory.

All of that can be encapsulated by creating a directory with following files

• snippet.dg
• ncycles.txt
• prepare_memory.dg
• expect_registers.dg
• expect_memory.dg

This would enable writing more complicated testcases more easily.