To reproduce:
1. Open attached project;
2. Choose "TestShader" shader in the Assets folder;
3. In the Inspector, disable "Skip unused shader_features";
4. Compile Shader for D3D9.

Expected result: Editor compiles shader, no errors are thrown.
Actual result: Error is thrown: "Shader error in 'Test Shader': texld/texldb/texldp/dsx/dsy instructions with r# as source cannot be used inside dynamic conditional 'if' blocks, dynamic conditional subroutine calls, or loop/rep with break*. at line 50 (on d3d9)" when compiling shader for D3D9.

Reproduced on versions: 5.6.0a1, 5.6.1p1, 2017.1.0b5.
Not reproduced on version: 5.5.3p3.
Regression introduced in: 5.6.0a1.