[Nouveau] [PATCH 2/2] nv50/ir: Fold IMM into MAD

[Ilia Mirkin]

On Fri, Jan 23, 2015 at 1:46 PM, Roy Spliet <rspliet at eclipso.eu> wrote:
> Add a specific optimisation pass for NV50 to check whether SRC0 or SRC1 is
> a MOV dst, IMM. If so: fold the IMM in and try to drop the MOV. Must be
> done post-RA because it requires that SDST == SSRC2.
>
> V2: improve readability and add comments to clarify decisions
> V3: Remove redundant code... compiler already attempts to put the IMM in
> SSRC1
>
> Signed-off-by: Roy Spliet <rspliet at eclipso.eu>

Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>

> ---
>  .../drivers/nouveau/codegen/nv50_ir_peephole.cpp   | 53 ++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
>
> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> index 21d20ca..62d2ef7 100644
> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> @@ -2259,6 +2259,56 @@ FlatteningPass::tryPredicateConditional(BasicBlock *bb)
>
>  // =============================================================================
>
> +// Fold Immediate into MAD; must be done after register allocation due to
> +// constraint SDST == SSRC2
> +// TODO:
> +// Does NVC0+ have other situations where this pass makes sense?
> +class NV50PostRaConstantFolding : public Pass
> +{
> +private:
> +   virtual bool visit(BasicBlock *);
> +};
> +
> +bool
> +NV50PostRaConstantFolding::visit(BasicBlock *bb)
> +{
> +   Value *vtmp;
> +   Instruction *def;
> +
> +   for (Instruction *i = bb->getFirst(); i; i = i->next) {
> +      switch (i->op) {
> +      case OP_MAD:
> +         if (i->def(0).getFile() != FILE_GPR ||
> +             i->src(0).getFile() != FILE_GPR ||
> +             i->src(1).getFile() != FILE_GPR ||
> +             i->src(2).getFile() != FILE_GPR ||
> +             i->getDef(0)->reg.data.id != i->getSrc(2)->reg.data.id)
> +            break;
> +
> +         def = i->getSrc(1)->getInsn();
> +         if (def->op == OP_MOV && def->src(0).getFile() == FILE_IMMEDIATE) {
> +            vtmp = i->getSrc(1);
> +            i->setSrc(1, def->getSrc(0));
> +
> +            /* There's no post-RA dead code elimination, so do it here
> +             * XXX: if we add more code-removing post-RA passes, we might
> +             *      want to create a post-RA dead-code elim pass */
> +            if (vtmp->refCount() == 0)
> +               delete_Instruction(bb->getProgram(), def);
> +
> +            break;
> +         }
> +         break;
> +      default:
> +         break;
> +      }
> +   }
> +
> +   return true;
> +}
> +
> +// =============================================================================
> +
>  // Common subexpression elimination. Stupid O^2 implementation.
>  class LocalCSE : public Pass
>  {
> @@ -2629,6 +2679,9 @@ bool
>  Program::optimizePostRA(int level)
>  {
>     RUN_PASS(2, FlatteningPass, run);
> +   if (getTarget()->getChipset() < 0xc0)
> +      RUN_PASS(2, NV50PostRaConstantFolding, run);
> +
>     return true;
>  }
>
> --
> 2.1.0
>
>
>
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