[Mesa-dev] [Bug 70920] [PIGLIT, radeonsi] SIGSEGV for shaders/glsl-fs-inline-explosion

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Nov 19 12:58:23 PST 2013


--- Comment #3 from Ian Romanick <idr at freedesktop.org> ---
The cause has been known since the tests were added in 2010:

commit 656cc65b2d3782c078d36342d0deec9886514520
Author: Luca Barbieri <luca at luca-barbieri.com>
Date:   Mon Sep 6 04:56:05 2010 +0200

    add GLSL inlining/unroll limit tests, currently failing

    The current GLSL compiler inlines everything indiscriminately,
    and unrolls all loops that have a small iteration count.

    This is a bad idea, because it can lead to exponential growth of
    the code, as these test cases illustrate.

    On a naive implementation (like current Mesa) these tests will
    attempt to allocate more than 2^64 bytes of RAM, ensuring failure.

    A smart implementation will instead generate actual calls/loops, and the
    test passes, since the branch protecting the functions/loops is not taken.

    Currently they aren't added to any profile since they obviously cause
    piglit to hang until memory is exhausted, possibly causing lots of
    swap thrashing.

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