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

[Andy Furniss]

Samuel Pitoiset wrote:

This patch has a minor issue for me using radeonsi on tonga.

ffmpeg vaapi hwdecode by cli or via mpv now produces the message

mesa: for the -simplifycfg-sink-common option: may only occur zero or 
one times!

>
> 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
>>
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