On Mon, Jan 18, 2016 at 4:14 AM, Ilia Mirkin <imir...@alum.mit.edu> wrote:
> The whole point of inlining sources is to reduce loads. We can end up in
> a situation where one value is used a lot of times, and one value is
> used only once per instruction. The once-per-instruction one is the one
> that should get inlined, but with the previous algorithm, it was given
> no preference.
>
> This flips things around to preferring putting less-referenced values
> into src1 which increases the likelihood of them being inlined.
>
> While we're at it, adjust the heuristic to not treat 0 as an immediate,
> as well as (effectively) check for situations where LIMMs can't be
> loaded. All this yields improvements on nvc0:
>
> total instructions in shared programs : 6261157 -> 6255985 (-0.08%)
> total gprs used in shared programs : 945082 -> 943417 (-0.18%)
> total local used in shared programs : 30372 -> 30288 (-0.28%)
> total bytes used in shared programs : 50089256 -> 50047880 (-0.08%)
>
> local gpr inst bytes
> helped 21 822 3332 3332
> hurt 0 278 565 565
>
> And more importantly avoids generating really bad code with SSBOs, where
> we end up checking a lot of different values (usually immediates) against
> the length.
>
> On nv50 the effect is less pronounced, although it does seem to, on
> average, pack the instructions better (instructions went up but bytes
> went down):
>
> total instructions in shared programs : 6346564 -> 6347676 (0.02%)
> total gprs used in shared programs : 728719 -> 725883 (-0.39%)
> total local used in shared programs : 3552 -> 3552 (0.00%)
> total bytes used in shared programs : 43995688 -> 43977840 (-0.04%)
>
> local gpr inst bytes
> helped 0 1326 3111 3677
> hurt 0 868 3572 3108
>
> Signed-off-by: Ilia Mirkin <imir...@alum.mit.edu>
> ---
> .../drivers/nouveau/codegen/nv50_ir_peephole.cpp | 26
> +++++++++++++---------
> 1 file changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> index f5c590e..4d82938 100644
> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> @@ -171,7 +171,10 @@ LoadPropagation::isImmdLoad(Instruction *ld)
> if (!ld || (ld->op != OP_MOV) ||
> ((typeSizeof(ld->dType) != 4) && (typeSizeof(ld->dType) != 8)))
> return false;
> - return ld->src(0).getFile() == FILE_IMMEDIATE;
> +
> + // A 0 can be replaced with a register, so it doesn't count as an
> immediate.
> + ImmediateValue val;
> + return ld->src(0).getImmediate(val) && !val.isInteger(0);
> }
>
> bool
> @@ -187,7 +190,8 @@ LoadPropagation::isAttribOrSharedLoad(Instruction *ld)
> void
> LoadPropagation::checkSwapSrc01(Instruction *insn)
> {
> - if (!prog->getTarget()->getOpInfo(insn).commutative)
> + const Target *targ = prog->getTarget();
> + if (!targ->getOpInfo(insn).commutative)
> if (insn->op != OP_SET && insn->op != OP_SLCT)
> return;
> if (insn->src(1).getFile() != FILE_GPR)
> @@ -196,14 +200,16 @@ LoadPropagation::checkSwapSrc01(Instruction *insn)
> Instruction *i0 = insn->getSrc(0)->getInsn();
> Instruction *i1 = insn->getSrc(1)->getInsn();
>
> - if (isCSpaceLoad(i0)) {
> - if (!isCSpaceLoad(i1))
> - insn->swapSources(0, 1);
> - else
> - return;
> - } else
> - if (isImmdLoad(i0)) {
> - if (!isCSpaceLoad(i1) && !isImmdLoad(i1))
> + // Swap sources to inline the less frequently used source. That way,
> + // optimistically, it will eventually be able to remove the instruction.
> + int i0refs = insn->getSrc(0)->refCount();
> + int i1refs = insn->getSrc(1)->refCount();
> +
> + if (isCSpaceLoad(i0) || isImmdLoad(i0)) {
> + if (targ->insnCanLoad(insn, 1, i0) && (
Changing this to be
if ((isCSpace || isImmd) && insnCanLoad)) {
gets much better nv50 improvements (and no nvc0 changes) since it can
then try to do the attrib swap (which will never lead to anything good
on nvc0). I won't re-send a v2 though.
> + (!isImmdLoad(i1) && !isCSpaceLoad(i1)) ||
> + !targ->insnCanLoad(insn, 1, i1) ||
> + i0refs < i1refs))
> insn->swapSources(0, 1);
> else
> return;
> --
> 2.4.10
>
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/mesa-dev
