nir: Add a new pass to lower array dereferences on vectors
authorJason Ekstrand <jason.ekstrand@intel.com>
Mon, 11 Mar 2019 23:47:39 +0000 (18:47 -0500)
committerJason Ekstrand <jason.ekstrand@intel.com>
Sat, 16 Mar 2019 04:10:27 +0000 (23:10 -0500)
This pass was originally written for lowering TCS output reads and
writes but it is also applicable just about anything including UBOs,
SSBOs, and shared variables.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
src/compiler/Makefile.sources
src/compiler/nir/meson.build
src/compiler/nir/nir.h
src/compiler/nir/nir_lower_array_deref_of_vec.c [new file with mode: 0644]

index 30e3b1826ec3b6686094f6c15eae71800996b844..722cfbb25a8856677d6f2e9c93e0468abd2fed2e 100644 (file)
@@ -230,6 +230,7 @@ NIR_FILES = \
        nir/nir_lower_alpha_test.c \
        nir/nir_lower_alu.c \
        nir/nir_lower_alu_to_scalar.c \
+       nir/nir_lower_array_deref_of_vec.c \
        nir/nir_lower_atomics_to_ssbo.c \
        nir/nir_lower_bitmap.c \
        nir/nir_lower_bit_size.c \
index b46bf8f2ebf3e75514f55c8d7b58abf9b023a15b..4f1efb5c6d3c9baa49d5595f8fc9c468b8f4c028 100644 (file)
@@ -112,6 +112,7 @@ files_libnir = files(
   'nir_lower_alu.c',
   'nir_lower_alu_to_scalar.c',
   'nir_lower_alpha_test.c',
+  'nir_lower_array_deref_of_vec.c',
   'nir_lower_atomics_to_ssbo.c',
   'nir_lower_bitmap.c',
   'nir_lower_bool_to_float.c',
index b25842834ae0434efa0edf511a47f70a587ce0c7..067287fab1ce67a8da6338c6989281afa57a15a4 100644 (file)
@@ -2973,6 +2973,16 @@ void nir_fixup_deref_modes(nir_shader *shader);
 
 bool nir_lower_global_vars_to_local(nir_shader *shader);
 
+typedef enum {
+   nir_lower_direct_array_deref_of_vec_load     = (1 << 0),
+   nir_lower_indirect_array_deref_of_vec_load   = (1 << 1),
+   nir_lower_direct_array_deref_of_vec_store    = (1 << 2),
+   nir_lower_indirect_array_deref_of_vec_store  = (1 << 3),
+} nir_lower_array_deref_of_vec_options;
+
+bool nir_lower_array_deref_of_vec(nir_shader *shader, nir_variable_mode modes,
+                                  nir_lower_array_deref_of_vec_options options);
+
 bool nir_lower_indirect_derefs(nir_shader *shader, nir_variable_mode modes);
 
 bool nir_lower_locals_to_regs(nir_shader *shader);
diff --git a/src/compiler/nir/nir_lower_array_deref_of_vec.c b/src/compiler/nir/nir_lower_array_deref_of_vec.c
new file mode 100644 (file)
index 0000000..2a70dd1
--- /dev/null
@@ -0,0 +1,190 @@
+/*
+ * Copyright © 2019 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.h"
+#include "nir_builder.h"
+
+static void
+build_write_masked_store(nir_builder *b, nir_deref_instr *vec_deref,
+                         nir_ssa_def *value, unsigned component)
+{
+   assert(value->num_components == 1);
+   unsigned num_components = glsl_get_components(vec_deref->type);
+   assert(num_components > 1 && num_components <= NIR_MAX_VEC_COMPONENTS);
+
+   nir_ssa_def *u = nir_ssa_undef(b, 1, value->bit_size);
+   nir_ssa_def *comps[NIR_MAX_VEC_COMPONENTS];
+   for (unsigned i = 0; i < num_components; i++)
+      comps[i] = (i == component) ? value : u;
+
+   nir_ssa_def *vec = nir_vec(b, comps, num_components);
+   nir_store_deref(b, vec_deref, vec, (1u << component));
+}
+
+static void
+build_write_masked_stores(nir_builder *b, nir_deref_instr *vec_deref,
+                          nir_ssa_def *value, nir_ssa_def *index,
+                          unsigned start, unsigned end)
+{
+   if (start == end - 1) {
+      build_write_masked_store(b, vec_deref, value, start);
+   } else {
+      unsigned mid = start + (end - start) / 2;
+      nir_push_if(b, nir_ilt(b, index, nir_imm_int(b, mid)));
+      build_write_masked_stores(b, vec_deref, value, index, start, mid);
+      nir_push_else(b, NULL);
+      build_write_masked_stores(b, vec_deref, value, index, mid, end);
+      nir_pop_if(b, NULL);
+   }
+}
+
+static bool
+nir_lower_array_deref_of_vec_impl(nir_function_impl *impl,
+                                  nir_variable_mode modes,
+                                  nir_lower_array_deref_of_vec_options options)
+{
+   bool progress = false;
+
+   nir_builder b;
+   nir_builder_init(&b, impl);
+
+   nir_foreach_block(block, impl) {
+      nir_foreach_instr_safe(instr, block) {
+         if (instr->type != nir_instr_type_intrinsic)
+            continue;
+
+         nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+         assert(intrin->intrinsic != nir_intrinsic_copy_deref);
+
+         if (intrin->intrinsic != nir_intrinsic_load_deref &&
+             intrin->intrinsic != nir_intrinsic_interp_deref_at_centroid &&
+             intrin->intrinsic != nir_intrinsic_interp_deref_at_sample &&
+             intrin->intrinsic != nir_intrinsic_interp_deref_at_offset &&
+             intrin->intrinsic != nir_intrinsic_store_deref)
+            continue;
+
+         nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
+         if (!(deref->mode & modes))
+            continue;
+
+         /* We only care about array derefs that act on vectors */
+         if (deref->deref_type != nir_deref_type_array)
+            continue;
+
+         nir_deref_instr *vec_deref = nir_deref_instr_parent(deref);
+         if (!glsl_type_is_vector(vec_deref->type))
+            continue;
+
+         assert(intrin->num_components == 1);
+         unsigned num_components = glsl_get_components(vec_deref->type);
+         assert(num_components > 1 && num_components <= NIR_MAX_VEC_COMPONENTS);
+
+         b.cursor = nir_after_instr(&intrin->instr);
+
+         if (intrin->intrinsic == nir_intrinsic_store_deref) {
+            assert(intrin->src[1].is_ssa);
+            nir_ssa_def *value = intrin->src[1].ssa;
+
+            if (nir_src_is_const(deref->arr.index)) {
+               if (!(options & nir_lower_direct_array_deref_of_vec_store))
+                  continue;
+
+               unsigned index = nir_src_as_uint(deref->arr.index);
+               /* If index is OOB, we throw the old store away and don't
+                * replace it with anything.
+                */
+               if (index < num_components)
+                  build_write_masked_store(&b, vec_deref, value, index);
+            } else {
+               if (!(options & nir_lower_indirect_array_deref_of_vec_store))
+                  continue;
+
+               nir_ssa_def *index = nir_ssa_for_src(&b, deref->arr.index, 1);
+               build_write_masked_stores(&b, vec_deref, value, index,
+                                         0, num_components);
+            }
+            nir_instr_remove(&intrin->instr);
+
+            progress = true;
+         } else {
+            if (nir_src_is_const(deref->arr.index)) {
+               if (!(options & nir_lower_direct_array_deref_of_vec_load))
+                  continue;
+            } else {
+               if (!(options & nir_lower_indirect_array_deref_of_vec_load))
+                  continue;
+            }
+
+            /* Turn the load into a vector load */
+            nir_instr_rewrite_src(&intrin->instr, &intrin->src[0],
+                                  nir_src_for_ssa(&vec_deref->dest.ssa));
+            intrin->dest.ssa.num_components = num_components;
+            intrin->num_components = num_components;
+
+            nir_ssa_def *index = nir_ssa_for_src(&b, deref->arr.index, 1);
+            nir_ssa_def *scalar =
+               nir_vector_extract(&b, &intrin->dest.ssa, index);
+            if (scalar->parent_instr->type == nir_instr_type_ssa_undef) {
+               nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
+                                        nir_src_for_ssa(scalar));
+               nir_instr_remove(&intrin->instr);
+            } else {
+               nir_ssa_def_rewrite_uses_after(&intrin->dest.ssa,
+                                              nir_src_for_ssa(scalar),
+                                              scalar->parent_instr);
+            }
+            progress = true;
+         }
+      }
+   }
+
+   if (progress) {
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+   }
+
+   return progress;
+}
+
+/* Lowers away array dereferences on vectors
+ *
+ * These are allowed on certain variable types such as SSBOs and TCS outputs.
+ * However, not everyone can actually handle them everywhere.  There are also
+ * cases where we want to lower them for performance reasons.
+ *
+ * This patch assumes that copy_deref instructions have already been lowered.
+ */
+bool
+nir_lower_array_deref_of_vec(nir_shader *shader, nir_variable_mode modes,
+                             nir_lower_array_deref_of_vec_options options)
+{
+   bool progress = false;
+
+   nir_foreach_function(function, shader) {
+      if (function->impl &&
+          nir_lower_array_deref_of_vec_impl(function->impl, modes, options))
+         progress = true;
+   }
+
+   return progress;
+}