Steps to reproduce:

1) Download attached project 'ShaderTest.zip' and open in Unity
2) Switch platform to PC, Mac & Linux Standalone
3) In the Player Settings, make sure Graphics API is set to Direct3D9
4) Open 'Main' scene and press Play
5) Press 'G' on the keyboard
Observe the crash:
========== OUTPUTING STACK TRACE ==================

0x00007FFAA7A7622C (d3d9) Direct3DCreate9Ex
0x00007FFAA7A909B5 (d3d9) Direct3DCreate9Ex
0x0000000140B043DB (Unity) D3D9VertexShader::Create
0x0000000140B05981 (Unity) D3D9VertexShader::D3D9VertexShader
0x0000000140AF80D2 (Unity) CreateGpuProgram

Expected result: Shader should be loaded without crashing the Editor
Actual result: Shader makes Editor to crash when using Direct3D9 Graphics API

Reproduced with:
5.6.0a1, 5.6.3p2, 2017.1.1f1, 2017.2.0b10

Not reproduced with:
5.5.4p4

Regression since:
5.6.0a1

Tested using Windows 10 machine

Note that Direct3D9 was removed in Unity 2017.3.x