nir: Introduce new nir_intrinsic_load_per_vertex_input intrinsics.

Geometry and tessellation shaders process multiple vertices; their
inputs are arrays indexed by the vertex number.  While GLSL makes
this look like a normal array, it can be very different behind the
scenes.

On Intel hardware, all inputs for a particular vertex are stored
together - as if they were grouped into a single struct.  This means
that consecutive elements of these top-level arrays are not contiguous.
In fact, they may sometimes be in completely disjoint memory segments.

NIR's existing load_input intrinsics are awkward for this case, as they
distill everything down to a single offset.  We'd much rather keep the
vertex ID separate, but build up an offset as normal beyond that.

This patch introduces new nir_intrinsic_load_per_vertex_input
intrinsics to handle this case.  They work like ordinary load_input
intrinsics, but have an extra source (src[0]) which represents the
outermost array index.

v2: Rebase on earlier refactors.
v3: Use ssa defs instead of nir_srcs, rebase on earlier refactors.

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/glsl/nir/nir_print.c b/src/glsl/nir/nir_print.c
index 3936bae078b..09663996869 100644
--- a/src/glsl/nir/nir_print.c
+++ b/src/glsl/nir/nir_print.c
@@ -443,6 +443,8 @@ print_intrinsic_instr(nir_intrinsic_instr *instr, print_state *state)
       break;
    case nir_intrinsic_load_input:
    case nir_intrinsic_load_input_indirect:
+   case nir_intrinsic_load_per_vertex_input:
+   case nir_intrinsic_load_per_vertex_input_indirect:
       var_list = &state->shader->inputs;
       break;
    case nir_intrinsic_store_output: