[llvm-bugs] [Bug 35397] New: [AMDGPU][MC][GFX8][GFX9] Use of bound_ctrl is incompatible with SP3

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=35397

            Bug ID: 35397
           Summary: [AMDGPU][MC][GFX8][GFX9] Use of bound_ctrl is
                    incompatible with SP3
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: AMDGPU
          Assignee: unassignedbugs at nondot.org
          Reporter: dpreobrazhensky at luxoft.com
                CC: llvm-bugs at lists.llvm.org

SP3 handles bound_ctrl differently in gfx8 and gfx9.
This causes incompatibility and inconsistency issues.

---------------------------------------------------------------------
Modifier          SP3 meaning            decoded by SP3 as
                 gfx8      gfx9        gfx8             gfx9
---------------------------------------------------------------------
bound_ctrl=0     set bit   clr bit     bound_ctrl=0     <omitted>
bound_ctrl=1     set bit   set bit     bound_ctrl=0     bound_ctrl=1
<omitted>        clr bit   clr bit     <omitted>        <omitted>
---------------------------------------------------------------------

Our assembler is incompatible with SP3 implementation: 

-------------------------------------------------------------
Modifier        LLVM Asm meaning       decoded by LLVM Asm as
-------------------------------------------------------------
bound_ctrl=0    set bit                bound_ctrl=0
bound_ctrl=1    <not supported>        N/A
<omitted>       clr bit                <omitted>
-------------------------------------------------------------

I believe we should improve current implementation:
- make it more compatible with SP3;
- make it more consistent.

I see the following options:

a) Do not change anything;
b) Strictly follow SP3 implementation;
c) Mimic SP3 gfx8 implementation for both gfx8 and gfx9;
d) Mimic SP3 gfx9 implementation for both gfx8 and gfx9.

Artem and Sam suggested option c) while I tend to prefer option d).
Matt, what is your opinion?

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