[Mesa-dev] [PATCH 1/2] gallium/tgsi: add support for DEMOTE and READ_HELPER opcodes

[Marek Olšák]

Reviewed-by: Marek Olšák <marek.olsak at amd.com>

Marek

On Wed, Oct 2, 2019 at 7:49 PM Ilia Mirkin <imirkin at alum.mit.edu> wrote:

> This mirrors the intrinsics in the GLSL IR. One could imagine an
> alternate definition where reading the semantic would account for the
> READ_HELPER functionality, but that feels potentially dodgy and could be
> subject to CSE unpleasantness.
>
> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
> ---
>  .../auxiliary/tgsi/tgsi_info_opcodes.h        |  4 ++--
>  src/gallium/docs/source/tgsi.rst              | 21 +++++++++++++++++++
>  src/gallium/include/pipe/p_shader_tokens.h    |  4 ++--
>  src/mesa/state_tracker/st_glsl_to_tgsi.cpp    |  7 +++++--
>  4 files changed, 30 insertions(+), 6 deletions(-)
>
> diff --git a/src/gallium/auxiliary/tgsi/tgsi_info_opcodes.h
> b/src/gallium/auxiliary/tgsi/tgsi_info_opcodes.h
> index 0b9b264bc53..7aecda44b82 100644
> --- a/src/gallium/auxiliary/tgsi/tgsi_info_opcodes.h
> +++ b/src/gallium/auxiliary/tgsi/tgsi_info_opcodes.h
> @@ -29,11 +29,11 @@ OPCODE(1, 1, COMP, ROUND)
>  OPCODE(1, 1, REPL, EX2)
>  OPCODE(1, 1, REPL, LG2)
>  OPCODE(1, 2, REPL, POW)
> -OPCODE_GAP(31) /* removed */
> +OPCODE(0, 0, NONE, DEMOTE)
>  OPCODE(1, 1, COMP, U2I64)
>  OPCODE(1, 0, OTHR, CLOCK)
>  OPCODE(1, 1, COMP, I2I64)
> -OPCODE_GAP(35) /* removed */
> +OPCODE(1, 0, COMP, READ_HELPER)
>  OPCODE(1, 1, REPL, COS)
>  OPCODE(1, 1, COMP, DDX)
>  OPCODE(1, 1, COMP, DDY)
> diff --git a/src/gallium/docs/source/tgsi.rst
> b/src/gallium/docs/source/tgsi.rst
> index 287f4b72729..d58b23f024b 100644
> --- a/src/gallium/docs/source/tgsi.rst
> +++ b/src/gallium/docs/source/tgsi.rst
> @@ -681,6 +681,27 @@ This instruction replicates its result.
>    Unconditional discard.  Allowed in fragment shaders only.
>
>
> +.. opcode:: DEMOTE - Demote Invocation to a Helper
> +
> +  This demotes the current invocation to a helper, but continues
> +  execution (while KILL may or may not terminate the
> +  invocation). After this runs, all the usual helper invocation rules
> +  apply about discarding buffer and render target writes. This is
> +  useful for having accurate derivatives in the other invocations
> +  which have not been demoted.
> +
> +  Allowed in fragment shaders only.
> +
> +
> +.. opcode:: READ_HELPER - Reads Invocation Helper Status
> +
> +  This is identical to ``TGSI_SEMANTIC_HELPER_INVOCATION``, except
> +  this will read the current value, which might change as a result of
> +  a ``DEMOTE`` instruction.
> +
> +  Allowed in fragment shaders only.
> +
> +
>  .. opcode:: TXB - Texture Lookup With Bias
>
>    for cube map array textures and shadow cube maps, the bias value
> diff --git a/src/gallium/include/pipe/p_shader_tokens.h
> b/src/gallium/include/pipe/p_shader_tokens.h
> index b30a257df2f..5770eba0837 100644
> --- a/src/gallium/include/pipe/p_shader_tokens.h
> +++ b/src/gallium/include/pipe/p_shader_tokens.h
> @@ -376,11 +376,11 @@ enum tgsi_opcode {
>     TGSI_OPCODE_EX2                = 28,
>     TGSI_OPCODE_LG2                = 29,
>     TGSI_OPCODE_POW                = 30,
> -   /* gap */
> +   TGSI_OPCODE_DEMOTE             = 31,
>     TGSI_OPCODE_U2I64              = 32,
>     TGSI_OPCODE_CLOCK              = 33,
>     TGSI_OPCODE_I2I64              = 34,
> -   /* gap */
> +   TGSI_OPCODE_READ_HELPER        = 35,
>     TGSI_OPCODE_COS                = 36,
>     TGSI_OPCODE_DDX                = 37,
>     TGSI_OPCODE_DDY                = 38,
> diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
> b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
> index 799c161cfaf..be582f5f01c 100644
> --- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
> +++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
> @@ -4107,6 +4107,10 @@ glsl_to_tgsi_visitor::visit(ir_call *ir)
>        visit_generic_intrinsic(ir, TGSI_OPCODE_READ_INVOC);
>        return;
>
> +   case ir_intrinsic_helper_invocation:
> +      visit_generic_intrinsic(ir, TGSI_OPCODE_READ_HELPER);
> +      return;
> +
>     case ir_intrinsic_invalid:
>     case ir_intrinsic_generic_load:
>     case ir_intrinsic_generic_store:
> @@ -4120,7 +4124,6 @@ glsl_to_tgsi_visitor::visit(ir_call *ir)
>     case ir_intrinsic_generic_atomic_comp_swap:
>     case ir_intrinsic_begin_invocation_interlock:
>     case ir_intrinsic_end_invocation_interlock:
> -   case ir_intrinsic_helper_invocation:
>        unreachable("Invalid intrinsic");
>     }
>  }
> @@ -4631,7 +4634,7 @@ glsl_to_tgsi_visitor::visit(ir_discard *ir)
>  void
>  glsl_to_tgsi_visitor::visit(ir_demote *ir)
>  {
> -   assert(!"demote statement unsupported");
> +   emit_asm(ir, TGSI_OPCODE_DEMOTE);
>  }
>
>  void
> --
> 2.21.0
>
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> mesa-dev at lists.freedesktop.org
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