[Mesa-dev] [PATCH v2 08/18] compiler/nir: add a lowering pass to convert the bit size of ALU operations
Iago Toral Quiroga
itoral at igalia.com
Mon Apr 30 14:18:16 UTC 2018
Not all bit-sizes may be supported natively in hardware for all operations.
This pass allows drivers to lower such operations to a bit-size that is
actually supported and then converts the result back to the original
bit-size.
Compiler backends control which operations and wich bit-sizes require
the lowering through a callback function.
v2: generalize this pass and make it available in NIR core (Rob, Jason)
---
src/compiler/Makefile.sources | 1 +
src/compiler/nir/meson.build | 1 +
src/compiler/nir/nir.h | 6 ++
src/compiler/nir/nir_lower_bit_size.c | 127 ++++++++++++++++++++++++++++++++++
4 files changed, 135 insertions(+)
create mode 100644 src/compiler/nir/nir_lower_bit_size.c
diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
index aca9dab476..b5321588be 100644
--- a/src/compiler/Makefile.sources
+++ b/src/compiler/Makefile.sources
@@ -237,6 +237,7 @@ NIR_FILES = \
nir/nir_lower_phis_to_scalar.c \
nir/nir_lower_regs_to_ssa.c \
nir/nir_lower_returns.c \
+ nir/nir_lower_bit_size.c \
nir/nir_lower_samplers.c \
nir/nir_lower_samplers_as_deref.c \
nir/nir_lower_subgroups.c \
diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
index b28a565d0c..62fe5167d3 100644
--- a/src/compiler/nir/meson.build
+++ b/src/compiler/nir/meson.build
@@ -144,6 +144,7 @@ files_libnir = files(
'nir_lower_vec_to_movs.c',
'nir_lower_wpos_center.c',
'nir_lower_wpos_ytransform.c',
+ 'nir_lower_bit_size.c',
'nir_metadata.c',
'nir_move_vec_src_uses_to_dest.c',
'nir_normalize_cubemap_coords.c',
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index f3326e6df9..e7f2b145b3 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2763,6 +2763,12 @@ bool nir_lower_to_source_mods(nir_shader *shader);
bool nir_lower_gs_intrinsics(nir_shader *shader);
+typedef unsigned (*nir_lower_bit_size_callback)(const nir_alu_instr *, void *);
+
+bool nir_lower_bit_size(nir_shader *shader,
+ nir_lower_bit_size_callback callback,
+ void *callback_data);
+
typedef enum {
nir_lower_imul64 = (1 << 0),
nir_lower_isign64 = (1 << 1),
diff --git a/src/compiler/nir/nir_lower_bit_size.c b/src/compiler/nir/nir_lower_bit_size.c
new file mode 100644
index 0000000000..8e0fd663a1
--- /dev/null
+++ b/src/compiler/nir/nir_lower_bit_size.c
@@ -0,0 +1,127 @@
+/*
+ * Copyright © 2018 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "nir_builder.h"
+
+/**
+ * Some ALU operations may not be supported in hardware in specific bit-sizes.
+ * This pass allows implementations to selectively lower such operations to
+ * a bit-size that is supported natively and the converts the result back to
+ * the original bit-size.
+ */
+static nir_ssa_def *
+convert_to_bit_size(nir_builder *bld,
+ nir_ssa_def *src,
+ nir_alu_type type,
+ unsigned bit_size)
+{
+ nir_alu_type base_type = nir_alu_type_get_base_type(type);
+ nir_alu_type lowered_type = bit_size | base_type;
+
+ nir_op opcode =
+ nir_type_conversion_op(type, lowered_type, nir_rounding_mode_undef);
+
+ return nir_build_alu(bld, opcode, src, NULL, NULL, NULL);
+}
+
+static void
+lower_instr(nir_builder *bld, nir_alu_instr *alu, unsigned bit_size)
+{
+ const nir_op op = alu->op;
+
+ bld->cursor = nir_before_instr(&alu->instr);
+
+ /* Convert each source to the requested bit-size */
+ nir_ssa_def *srcs[4] = { NULL, NULL, NULL, NULL };
+ const unsigned num_inputs = nir_op_infos[op].num_inputs;
+ for (unsigned i = 0; i < num_inputs; i++) {
+ nir_ssa_def *src = nir_ssa_for_alu_src(bld, alu, i);
+
+ nir_alu_type type = nir_op_infos[op].input_types[i];
+ unsigned type_size = nir_alu_type_get_type_size(type);
+ if (type_size == 0)
+ srcs[i] = convert_to_bit_size(bld, src, type, bit_size);
+ else
+ srcs[i] = src;
+ }
+
+ /* Emit the lowered ALU instruction */
+ nir_ssa_def *lowered_dst =
+ nir_build_alu(bld, op, srcs[0], srcs[1], srcs[2], srcs[3]);
+
+ /* Convert result back to the original bit-size */
+ unsigned dst_bit_size = alu->dest.dest.ssa.bit_size;
+ nir_alu_type type = nir_op_infos[op].output_type;
+ nir_ssa_def *dst = convert_to_bit_size(bld, lowered_dst, type, dst_bit_size);
+ nir_ssa_def_rewrite_uses(&alu->dest.dest.ssa, nir_src_for_ssa(dst));
+}
+
+static bool
+lower_impl(nir_function_impl *impl,
+ nir_lower_bit_size_callback callback,
+ void *callback_data)
+{
+ nir_builder b;
+ nir_builder_init(&b, impl);
+ bool progress = false;
+
+ nir_foreach_block(block, impl) {
+ nir_foreach_instr_safe(instr, block) {
+ if (instr->type == nir_instr_type_alu) {
+ nir_alu_instr *alu = nir_instr_as_alu(instr);
+ assert(alu->dest.dest.is_ssa);
+
+ unsigned lower_bit_size = callback(alu, callback_data);
+ if (lower_bit_size == 0)
+ continue;
+
+ assert(lower_bit_size != alu->dest.dest.ssa.bit_size);
+
+ lower_instr(&b, alu, lower_bit_size);
+ progress = true;
+ }
+ }
+ }
+
+ if (progress) {
+ nir_metadata_preserve(impl, nir_metadata_block_index |
+ nir_metadata_dominance);
+ }
+
+ return progress;
+}
+
+bool
+nir_lower_bit_size(nir_shader *shader,
+ nir_lower_bit_size_callback callback,
+ void *callback_data)
+{
+ bool progress = false;
+
+ nir_foreach_function(function, shader) {
+ if (function->impl)
+ progress |= lower_impl(function->impl, callback, callback_data);
+ }
+
+ return progress;
+}
--
2.14.1
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