Short HLSL shader that causes an internal compiler error

MinRepo.hlsl

int solve(float x)
{
	if (x < 0)
	{
		return 0;
	}
	// 1>MinRepo.hlsl(7,2): warning X4000: use of potentially uninitialized variable (solve)
	// 1>error X8000 : D3D11 Internal Compiler error : Invalid Bytecode: Negate modifier not allowed for operand #4 of opcode #6 (counts are 1-based).

	return 1;
}

int problem(float a)
{
	int num = 0;

	float b = (a < 0.0 ? -a : a);

	num += solve(b);

	b = (a < 0.0 ? a : -a);

	num += solve(b);

	return num;
}


float3 pixel(float value : TEXCOORD0) : SV_Target0
{
	float3 output = float3(0.0, 0.0, 0.0);

	int count = problem(value);

	if (count > 0)
	{
		output = float3(1, 0, 1);
	}
	else
	{
		output = float3(0, 0, 0);
	}

	return output;
}