[Mesa-dev] [PATCH] radeonsi: disable sinking common instructions down to the end block

[Samuel Pitoiset]

On 03/15/2017 02:01 PM, Marek Olšák wrote:
> On Wed, Mar 15, 2017 at 1:56 PM, Samuel Pitoiset
> <samuel.pitoiset at gmail.com> wrote:
>>
>>
>> On 03/15/2017 01:51 PM, Marek Olšák wrote:
>>>
>>> On Wed, Mar 15, 2017 at 1:21 AM, Samuel Pitoiset
>>> <samuel.pitoiset at gmail.com> wrote:
>>>>
>>>> Initially this was a workaround for a bug introduced in LLVM 4.0
>>>> in the SimplifyCFG pass that caused image instrinsics to disappear
>>>> (because they were badly sunk). Finally, this is a win because it
>>>> decreases SGPR spilling and increases the number of waves a bit.
>>>>
>>>> Although, shader-db results are good I think we might want to
>>>> remove it in the future once the issue is fixed. For now, enable
>>>> it for LLVM >= 4.0.
>>>>
>>>> This also fixes a rendering issue with the speedometer in Dirt Rally.
>>>>
>>>> More information can be found here https://reviews.llvm.org/D26348.
>>>>
>>>> Thanks to Dave Airlie for the patch.
>>>>
>>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99484
>>>> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
>>>> ---
>>>>
>>>> For those interested, here's the full shader-db report:
>>>>
>>>> https://hastebin.com/osepehehat.pas
>>>>
>>>>  src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c | 6 ++++++
>>>>  1 file changed, 6 insertions(+)
>>>>
>>>> diff --git a/src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c
>>>> b/src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c
>>>> index 5c63b732b3..4fb7a126e4 100644
>>>> --- a/src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c
>>>> +++ b/src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c
>>>> @@ -40,6 +40,7 @@
>>>>  #include <stdio.h>
>>>>  #include <llvm-c/Transforms/IPO.h>
>>>>  #include <llvm-c/Transforms/Scalar.h>
>>>> +#include <llvm-c/Support.h>
>>>>
>>>>  /* Data for if/else/endif and bgnloop/endloop control flow structures.
>>>>   */
>>>> @@ -124,6 +125,11 @@ static void init_amdgpu_target()
>>>>         LLVMInitializeAMDGPUTarget();
>>>>         LLVMInitializeAMDGPUTargetMC();
>>>>         LLVMInitializeAMDGPUAsmPrinter();
>>>> +
>>>> +#if HAVE_LLVM >= 0x0400
>>>> +       const char *argv[2] = {"mesa", "-simplifycfg-sink-common=false"};
>>>> +       LLVMParseCommandLineOptions(2, argv, NULL);
>>>> +#endif
>>>
>>>
>>> Would it possible to do:
>>> if (HAVE_LLVM >= 0x0400) {
>>> ...
>>> }
>>>
>>> Also, Cc stable?
>>
>>
>> Your call. But if the issue is fixed at some point in 4.0.1 or 5.0 we will
>> need to backport one more patch.
>
> Since this only disables the problematic optimization, we can keep it
> in stable and we won't have to backport anything else. (optimizations
> are usually not accepted in stable)

Fine by me. I will add the cc tag and the FIXME comment before pushing.
Thanks.

>
> Marek
>