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broadcom/compiler: add a set_a_flags_for_subgroup helper

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We will need this in the future to implement more subgroup operations,
so make this code available in a helper.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11620>
This commit is contained in:
Iago Toral Quiroga 2021-06-28 09:45:18 +02:00
parent b9f510087d
commit 5081de07f7
1 changed files with 29 additions and 24 deletions
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53
src/broadcom/compiler/nir_to_vir.c
View file

@ -2784,6 +2784,34 @@ emit_load_local_invocation_index(struct v3d_compile *c)
vir_uniform_ui(c, 32 - c->local_invocation_index_bits));
}
/* Various subgroup operations rely on the A flags, so this helper ensures that
* A flags represents currently active lanes in the subgroup.
*/
static void
set_a_flags_for_subgroup(struct v3d_compile *c)
{
/* MSF returns 0 for disabled lanes in compute shaders so
* PUSHZ will set A=1 for disabled lanes. We want the inverse
* of this but we don't have any means to negate the A flags
* directly, but we can do it by repeating the same operation
* with NORZ (A = ~A & ~Z).
*/
assert(c->s->info.stage == MESA_SHADER_COMPUTE);
vir_set_pf(c, vir_MSF_dest(c, vir_nop_reg()), V3D_QPU_PF_PUSHZ);
vir_set_uf(c, vir_MSF_dest(c, vir_nop_reg()), V3D_QPU_UF_NORZ);
/* If we are under non-uniform control flow we also need to
* AND the A flags with the current execute mask.
*/
if (vir_in_nonuniform_control_flow(c)) {
const uint32_t bidx = c->cur_block->index;
vir_set_uf(c, vir_XOR_dest(c, vir_nop_reg(),
c->execute,
vir_uniform_ui(c, bidx)),
V3D_QPU_UF_ANDZ);
}
}
static void
ntq_emit_intrinsic(struct v3d_compile *c, nir_intrinsic_instr *instr)
{
@ -3251,30 +3279,7 @@ ntq_emit_intrinsic(struct v3d_compile *c, nir_intrinsic_instr *instr)
break;
case nir_intrinsic_elect: {
/* Flafirst reads A flags so we need to make sure it reflects
* currently active lanes.
*
* MSF returns 0 for disabled lanes in compute shaders so
* PUSHZ will set A=1 for disabled lanes. We want the inverse
* of this but we don't have any means to negate the A flags
* directly, but we can do it by repeating the same operation
* with NORZ (A = ~A & ~Z).
*/
assert(c->s->info.stage == MESA_SHADER_COMPUTE);
vir_set_pf(c, vir_MSF_dest(c, vir_nop_reg()), V3D_QPU_PF_PUSHZ);
vir_set_uf(c, vir_MSF_dest(c, vir_nop_reg()), V3D_QPU_UF_NORZ);
/* If we are under non-uniform control flow we also need to
* AND the A flags with the current execute mask.
*/
if (vir_in_nonuniform_control_flow(c)) {
const uint32_t bidx = c->cur_block->index;
vir_set_uf(c, vir_XOR_dest(c, vir_nop_reg(),
c->execute,
vir_uniform_ui(c, bidx)),
V3D_QPU_UF_ANDZ);
}
set_a_flags_for_subgroup(c);
struct qreg first = vir_FLAFIRST(c);
/* Produce a boolean result from Flafirst */