[Mesa-dev] [PATCH v2 11/13] nvc0/ir: do not lower shared+atomics on GM107+

[Ilia Mirkin]

On Mar 31, 2016 12:09 PM, "Samuel Pitoiset" <samuel.pitoiset at gmail.com>
wrote:
>
> For Maxwell, the ATOMS instruction can be used to perform atomic
> operations on shared memory instead of this load/store lowering pass.
>
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>  .../nouveau/codegen/nv50_ir_lowering_nvc0.cpp        | 20
+++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git
a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
> index 7e6c87a..83e753e 100644
> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
> @@ -1294,10 +1294,14 @@ NVC0LoweringPass::handleATOM(Instruction *atom)
>        sv = SV_LBASE;
>        break;
>     case FILE_MEMORY_SHARED:
> -      if (targ->getChipset() >= NVISA_GK104_CHIPSET) {
> -         handleSharedATOMNVE4(atom);
> -      } else {
> -         handleSharedATOM(atom);
> +      if (targ->getChipset() < NVISA_GM107_CHIPSET) {
> +         // For Fermi/Kepler, we have to use ld lock/st unlock to perform
> +         // atomic operations on shared memory. For Maxwell, ATOMS is
enough.
> +         if (targ->getChipset() >= NVISA_GK104_CHIPSET) {
> +            handleSharedATOMNVE4(atom);
> +         } else {
> +            handleSharedATOM(atom);
> +         }
>        }

Or, with fewer branches...

If (<nve4) do nvc0 thing
Else if (<gm107) do nve4 thing

Which will drop the outer if, making it more comprehensible.

>        return true;
>     default:
> @@ -1326,9 +1330,11 @@ NVC0LoweringPass::handleATOM(Instruction *atom)
>  bool
>  NVC0LoweringPass::handleCasExch(Instruction *cas, bool needCctl)
>  {
> -   if (cas->src(0).getFile() == FILE_MEMORY_SHARED) {
> -      // ATOM_CAS and ATOM_EXCH are handled in handleSharedATOM().
> -      return false;
> +   if (targ->getChipset() < NVISA_GM107_CHIPSET) {
> +      if (cas->src(0).getFile() == FILE_MEMORY_SHARED) {
> +         // ATOM_CAS and ATOM_EXCH are handled in handleSharedATOM().
> +         return false;
> +      }
>     }
>
>     if (cas->subOp != NV50_IR_SUBOP_ATOM_CAS &&
> --
> 2.7.4
>
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