Adding dead discard leads to black image

[afd]

[Shaders, screenshots, error log, reproduction steps, platform info, etc.] [ZIP]

Recipient:

Variant:

WebGL viewer for recipient:

http://htmlpreview.github.io/?https://github.com/mc-imperial/shader-compiler-bugs/blob/master/angle/wrong-images/squares/webgl_viewer_recipient.html

WebGL viewer for variant:

http://htmlpreview.github.io/?https://github.com/mc-imperial/shader-compiler-bugs/blob/master/angle/wrong-images/squares/webgl_viewer_variant.html

The only difference between the shaders is that in the variant we add:

        if(((injectionSwitch.x > injectionSwitch.y)))
            {
                discard;
            }

Because injectionSwitch = (0.0, 1.0) the discard should be unreachable.

We suspect this is an ANGLE or Direct3D bug, because it manifests on two systems with Intel and NVIDIA GPU drivers respectively, with Chrome version 57.0.2987.110 (64-bit), and also in Firefox.

[0152la]

Did not observe differences on (none of the following use ANGLE): Chrome and Firefox on Archlinux running Mesa 13.0.3 on an Intel i7 Firefox on Ubuntu 16.04.2 running Mesa 17.0.1 on an AMD R9 *Chrome and Firefox on Ubuntu 16.10 running Nvidia proprietary drivers 375.39 on a GTX980M

Observed a linking failure on Edge on Windows 10 running Radeon 17.2.1 on an AMD R9 Fury. On the same machine, in Chrome (running ANGLE), observed the black box variant.

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Reported to ANGLE (though the Edge linking error suggests that it might be a Direct3D issue): https://bugs.chromium.org/p/angleproject/issues/detail?id=1949

[afd]

The issue was confirmed.