Some hardware, like i965, doesn't support group sizes greater than 32.
In that case, we can use the ballot32 intrinsic instead, which will
simplify our code generation.
---
src/compiler/nir/nir.h | 2 ++
src/compiler/nir/nir_intrinsics.h | 3 +++
src/compiler/nir/nir_opt_intrinsics.c | 17 +++++++++++++++++
src/intel/compiler/brw_compiler.c | 1 +
4 files changed, 23 insertions(+)
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 3591048574..a3d8df0b19 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1844,6 +1844,8 @@ typedef struct nir_shader_compiler_options {
*/
bool use_interpolated_input_intrinsics;
+ unsigned max_subgroup_size;
+
unsigned max_unroll_iterations;
} nir_shader_compiler_options;
diff --git a/src/compiler/nir/nir_intrinsics.h
b/src/compiler/nir/nir_intrinsics.h
index 96ecfbc338..61ad9f6643 100644
--- a/src/compiler/nir/nir_intrinsics.h
+++ b/src/compiler/nir/nir_intrinsics.h
@@ -106,6 +106,9 @@ INTRINSIC(ballot, 1, ARR(1), true, 1, 0, 0, xx, xx, xx,
NIR_INTRINSIC_CAN_ELIMIN
INTRINSIC(read_invocation, 2, ARR(0, 1), true, 0, 0, 0, xx, xx, xx,
NIR_INTRINSIC_CAN_ELIMINATE)
INTRINSIC(read_first_invocation, 1, ARR(0), true, 0, 0, 0, xx, xx, xx,
NIR_INTRINSIC_CAN_ELIMINATE)
+/* Equivalent to ballot, but only returns the low 32-bits */
+INTRINSIC(ballot32, 1, ARR(1), true, 1, 0, 0, xx, xx, xx,
NIR_INTRINSIC_CAN_ELIMINATE)
+
/*
* Memory barrier with semantics analogous to the compute shader
* groupMemoryBarrier(), memoryBarrierAtomicCounter(), memoryBarrierBuffer(),
diff --git a/src/compiler/nir/nir_opt_intrinsics.c
b/src/compiler/nir/nir_opt_intrinsics.c
index 0cd75d8b28..023e169a99 100644
--- a/src/compiler/nir/nir_opt_intrinsics.c
+++ b/src/compiler/nir/nir_opt_intrinsics.c
@@ -69,6 +69,23 @@ opt_intrinsics_impl(nir_function_impl *impl)
replacement = nir_imm_int(&b, NIR_TRUE);
break;
}
+ case nir_intrinsic_ballot: {
+ assert(b.shader->options->max_subgroup_size != 0);
+ if (b.shader->options->max_subgroup_size > 32)
+ continue;
+
+ nir_intrinsic_instr *ballot =
+ nir_intrinsic_instr_create(b.shader, nir_intrinsic_ballot32);
+ nir_ssa_dest_init(&ballot->instr, &ballot->dest, 1, 32, NULL);
+ ballot->src[0] = intrin->src[0];
+
+ nir_builder_instr_insert(&b, &ballot->instr);
+
+ replacement = nir_pack_64_2x32_split(&b,
+ &ballot->dest.ssa,
+ nir_imm_int(&b, 0));
+ break;
+ }
default:
break;
}
diff --git a/src/intel/compiler/brw_compiler.c
b/src/intel/compiler/brw_compiler.c
index 9ad5d8e4ee..6970bcb40f 100644
--- a/src/intel/compiler/brw_compiler.c
+++ b/src/intel/compiler/brw_compiler.c
@@ -57,6 +57,7 @@ static const struct nir_shader_compiler_options
scalar_nir_options = {
.lower_unpack_snorm_4x8 = true,
.lower_unpack_unorm_2x16 = true,
.lower_unpack_unorm_4x8 = true,
+ .max_subgroup_size = 64, /* FIXME */
.max_unroll_iterations = 32,
};
--
2.13.0
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