[Mesa-dev] [Bug 108935] [LLVM Regression, bisected] Witcher 3 Corrupted Terrain

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108935

Samuel Pitoiset <samuel.pitoiset at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[LLVM Regression] Witcher 3 |[LLVM Regression,bisected]
                   |Corrupted Terrain           |Witcher 3 Corrupted Terrain
                 CC|                            |nhaehnle at gmail.com

--- Comment #1 from Samuel Pitoiset <samuel.pitoiset at gmail.com> ---
The problem can be reproduced on Polaris using the attached RenderDoc capture.

Bisected to:

41f457ff4f2e1571126d778f897efd274d1993ba is the first bad commit
commit 41f457ff4f2e1571126d778f897efd274d1993ba
Author: Nicolai Haehnle <nhaehnle at gmail.com>
Date:   Thu Nov 29 11:06:26 2018 +0000

    AMDGPU/InsertWaitcnts: Remove the dependence on MachineLoopInfo

    Summary:
    MachineLoopInfo cannot be relied on for correctness, because it cannot
    properly recognize loops in irreducible control flow which can be
    introduced by late machine basic block optimization passes. See the new
    test case for the reduced form of an example that occurred in practice.

    Use a simple fixpoint iteration instead.

    In order to facilitate this change, refactor WaitcntBrackets so that it
    only tracks pending events and registers, rather than also maintaining
    state that is relevant for the high-level algorithm. Various accessor
    methods can be removed or made private as a consequence.

    Affects (in radv):
    -
dEQP-VK.glsl.loops.special.{for,while}_uniform_iterations.select_iteration_count_{fragment,vertex}

    Fixes: r345719 ("AMDGPU: Rewrite SILowerI1Copies to always stay on SALU")

    Reviewers: msearles, rampitec, scott.linder, kanarayan

    Subscribers: arsenm, kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr,
t-tye, llvm-commits, hakzsam

    Differential Revision: https://reviews.llvm.org/D54231

    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@347853
91177308-0d34-0410-b5e6-96231b3b80d8

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