https://bugs.freedesktop.org/show_bug.cgi?id=93761

Bug ID: 93761 Summary: A conditional discard in a fragment shader causes no depth writing at all 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: jlegg@feralinteractive.com QA Contact: dri-devel@lists.freedesktop.org

Created attachment 121116 --> https://bugs.freedesktop.org/attachment.cgi?id=121116&action=edit Test case

When rendering to an FBO with only a GL_DEPTH_COMPONENT16 depth buffer, with depth testing enabled, if a fragment shader has a conditional discard, nothing is written to the depth buffer for pixels which should not be discarded.

Platform: Fedora 22 x86_64 Mesa version: tested both git eaf7ec9 (from griever-mesa-git copr) and 10.6.9 (the default mesa package with Fedora 22). The bug occurred on both. GL Renderer string: Gallium 0.4 on AMD PITCAIRN (DRM 2.43.0, LLVM 3.7.1) GPU: AMD R9 270 with 2GB VRAM

Workaround: If you write to gl_FragDepth, only the intentionally discarded pixels are discarded.

I've attached a test case demonstrating the problem. It will fail an assertion on the machine with this bug. It should draw only on the even columns of pixels in the depth buffer, but nothing is drawn.