| Bug ID | 100303 |
|---|---|
| Summary | Adding a single, meaningless if-else to a shader source leads to different image |
| Product | Mesa |
| Version | git |
| Hardware | x86-64 (AMD64) |
| OS | Linux (All) |
| Status | NEW |
| Severity | normal |
| Priority | medium |
| Component | Drivers/Gallium/radeonsi |
| Assignee | dri-devel@lists.freedesktop.org |
| Reporter | h.evrard@imperial.ac.uk |
| QA Contact | dri-devel@lists.freedesktop.org |
Created attachment 130352 [details] Zip archive with files to reproduce See: https://github.com/mc-imperial/shader-compiler-bugs/issues/62 Steps to Reproduce: ------------------------------- 0. This bug seems to affect AMD GPU (tested on Tonga, see below for more config details) 1. Obtain and build the latest release of get-image, a simple tool that creates a .png image from a fragment shader https://github.com/mc-imperial/get-image 2. From a terminal, execute: /path/to/get_image/linux_out/install/bin/get_image original.frag This will create output.png, which should look like original.png 3. From a terminal, execute: /path/to/get_image/linux_out/install/bin/get_image variant.frag This will create output.png, which should look like variant.png Expected Results: ------------------------------- Both shaders should render an image that looks like original.png. This is because the only difference between the shader source files is the addition of an if-else whose if block is empty and else block contains the original code. We control the condition value to make sure it is always false at runtime. Diff: ``` 27a28,29 > uniform vec2 injectionSwitch; > 117a120,124 > if(injectionSwitch.x > injectionSwitch.y) > { > } > else > { 129a137 > } ``` The injectionSwitch uniform is always set to { 0.0, 1.0 }. The else block contains the original code, untouched. Actual Results: ------------------------------- The shaders render different images, which they should not: the shadow in the lower part of the ball disappears in the variant. Additional Information: ------------------------------- Some info on the system where the bug was found: - CPU: AMD A10-7850K Radeon R7, 12 Compute Cores 4C+8G - GPU: Advanced Micro Devices, Inc. [AMD/ATI] Tonga PRO [Radeon R9 285/380] - Mesa: 17.1.0-devel (git-08df015) - OS: Ubuntu 16.04, Linux 4.4.0-67-generic
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