[Mesa-dev] [PATCH] nv50/ir: Properly fold constants in SPLIT operation

[Ilia Mirkin]

Wait, this is actively buggy! How did this ever work :( I guess we
don't split immediates too frequently, and I was testing it with
zero's or something.

Can you figure out the commit where I added this idiotic code and add
a Fixes: tag?

Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>
Cc: mesa-stable at lists.freedesktop.org

On Mon, Jun 12, 2017 at 4:53 PM, Pierre Moreau <pierre.morrow at free.fr> wrote:
> Signed-off-by: Pierre Moreau <pierre.morrow at free.fr>
> ---
>  src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> index e032255178..57223d311c 100644
> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
> @@ -975,8 +975,9 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue &imm0, int s)
>        bld.setPosition(i, false);
>
>        uint8_t size = i->getDef(0)->reg.size;
> -      uint32_t mask = (1ULL << size) - 1;
> -      assert(size <= 32);
> +      uint8_t bitsize = size * 8;
> +      uint32_t mask = (1ULL << bitsize) - 1;
> +      assert(bitsize <= 32);
>
>        uint64_t val = imm0.reg.data.u64;
>        for (int8_t d = 0; i->defExists(d); ++d) {
> @@ -984,7 +985,7 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue &imm0, int s)
>           assert(def->reg.size == size);
>
>           newi = bld.mkMov(def, bld.mkImm((uint32_t)(val & mask)), TYPE_U32);

Is that what you want here? Should this be typeOfSize(size) ?

I guess you want to split this into 32-bit values anyways since that's
what everything processes... eventually we might want to play around
with the SIMD opcodes but probably not soon.

> -         val >>= size;
> +         val >>= bitsize;
>        }
>        delete_Instruction(prog, i);
>        break;
> --
> 2.13.1
>