Bug 107193

0e47ecb29acf8bdd213236d7306c47f8ec0e937f is the first bad commit
commit 0e47ecb29acf8bdd213236d7306c47f8ec0e937f
Author: Jose Maria Casanova Crespo <jmcasanova@igalia.com>
Date:   Mon Mar 26 14:59:46 2018 +0200
    intel/compiler: grf127 can not be dest when src and dest overlap in send
    
    Implement at brw_eu_validate the restriction from Intel Broadwell PRM,
    vol 07, section "Instruction Set Reference", subsection "EUISA
    Instructions", Send Message (page 990):
    
    "r127 must not be used for return address when there is a src and
    dest overlap in send instruction."
    
    v2: Style fixes (Matt Turner)
    
    Reviewed-by: Matt Turner <mattst88@gmail.com>
    Cc: 18.1 <mesa-stable@lists.freedesktop.org>

patch posted:
https://patchwork.freedesktop.org/patch/237606/

I've just posted a patch to deal with this new case that new validation rule detects:

https://patchwork.freedesktop.org/patch/237794/

Fixed by:

commit 62f37ee53d9d5388eecef94369893b5467349306
Author: Jose Maria Casanova Crespo <jmcasanova@igalia.com>
Date:   Wed Jul 11 11:19:20 2018 +0200

    i965/fs: unspills shoudn't use grf127 as dest since Gen8+
    
    At 232ed8980217dd65ab0925df28156f565b94b2e5 "i965/fs: Register allocator
    shoudn't use grf127 for sends dest" we didn't take into account the case
    of SEND instructions that are not send_from_grf. But since Gen7+ although
    the backend still uses MRFs internally for sends they are finally
    assigned to a GRFs.
    
    In the case of unspills the backend assigns directly as source its
    destination because it is suppose to be available. So we always have a
    source-destination overlap. If the reg_allocator assigns registers that
    include the grf127 we fail the validation rule that affects Gen8+
    "r127 must not be used for return address when there is a src and dest
    overlap in send instruction."
    
    So this patch activates the grf127_send_hack_node for Gen8+ and if we
    have any register spilled we add interferences to the destination of
    the unspill operations.
    
    We also need to avoid that opt_bank_conflicts() optimization, that runs
    after the register allocation, doesn't move things around, causing the
    grf127 to be used in the condition we were avoiding.
    
    Fixes piglit test tests/spec/arb_compute_shader/linker/bug-93840.shader_test
    and some shader-db crashed because of the grf127 validation rule..
    
    v2: make sure that opt_bank_conflicts() optimization doesn't change
    the use of grf127. (Caio)
    
    Found by Caio Marcelo de Oliveira Filho
    
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107193
    Fixes: 232ed89802 "i965/fs: Register allocator shoudn't use grf127 for sends dest"
    Cc: 18.1 <mesa-stable@lists.freedesktop.org>
    Cc: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
    Cc: Jason Ekstrand <jason@jlekstrand.net>
    
    Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>