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authorKenneth Graunke <[email protected]>2015-09-24 17:01:23 -0700
committerKenneth Graunke <[email protected]>2015-09-26 12:01:53 -0700
commit02530c5dc5dc88078f41fb134c7e0e3833c9f772 (patch)
treeb83732ce6a5af75c5a2912f1fcb0296381189333 /src
parentdf221f65e26199a74bc259d3f94e70637b843afa (diff)
nir: Add a function to count the number of vertices a GS emits.
Some hardware (such as Broadwell) can run geometry shaders more efficiently when the number of vertices emitted is statically known. This pass provides a way to obtain the constant vertex count, or -1 indicating that the vertex count is unknown/non-constant. Signed-off-by: Kenneth Graunke <[email protected]> Reviewed-by: Jordan Justen <[email protected]>
Diffstat (limited to 'src')
-rw-r--r--src/glsl/Makefile.sources1
-rw-r--r--src/glsl/nir/nir.h2
-rw-r--r--src/glsl/nir/nir_gs_count_vertices.c93
3 files changed, 96 insertions, 0 deletions
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index a8f4994cf34..32b6dba2e91 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -30,6 +30,7 @@ NIR_FILES = \
nir/nir_control_flow_private.h \
nir/nir_dominance.c \
nir/nir_from_ssa.c \
+ nir/nir_gs_count_vertices.c \
nir/nir_intrinsics.c \
nir/nir_intrinsics.h \
nir/nir_live_variables.c \
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 4f45770e02d..d0c7b04a49f 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1804,6 +1804,8 @@ void nir_dump_dom_frontier(nir_shader *shader, FILE *fp);
void nir_dump_cfg_impl(nir_function_impl *impl, FILE *fp);
void nir_dump_cfg(nir_shader *shader, FILE *fp);
+int nir_gs_count_vertices(nir_shader *shader);
+
bool nir_split_var_copies(nir_shader *shader);
void nir_lower_var_copy_instr(nir_intrinsic_instr *copy, void *mem_ctx);
diff --git a/src/glsl/nir/nir_gs_count_vertices.c b/src/glsl/nir/nir_gs_count_vertices.c
new file mode 100644
index 00000000000..e0bdf170d22
--- /dev/null
+++ b/src/glsl/nir/nir_gs_count_vertices.c
@@ -0,0 +1,93 @@
+/*
+ * Copyright © 2015 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 nir_intrinsic_instr *
+as_intrinsic(nir_instr *instr, nir_intrinsic_op op)
+{
+ if (instr->type != nir_instr_type_intrinsic)
+ return NULL;
+
+ nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+ if (intrin->intrinsic != op)
+ return NULL;
+
+ return intrin;
+}
+
+static nir_intrinsic_instr *
+as_set_vertex_count(nir_instr *instr)
+{
+ return as_intrinsic(instr, nir_intrinsic_set_vertex_count);
+}
+
+/**
+ * If a geometry shader emits a constant number of vertices, return the
+ * number of vertices. Otherwise, return -1 (unknown).
+ *
+ * This only works if you've used nir_lower_gs_intrinsics() to do vertex
+ * counting at the NIR level.
+ */
+int
+nir_gs_count_vertices(nir_shader *shader)
+{
+ int count = -1;
+
+ nir_foreach_overload(shader, overload) {
+ if (!overload->impl)
+ continue;
+
+ /* set_vertex_count intrinsics only appear in predecessors of the
+ * end block. So we don't need to walk all of them.
+ */
+ struct set_entry *entry;
+ set_foreach(overload->impl->end_block->predecessors, entry) {
+ nir_block *block = (nir_block *) entry->key;
+
+ nir_foreach_instr_reverse(block, instr) {
+ nir_intrinsic_instr *intrin = as_set_vertex_count(instr);
+ if (!intrin)
+ continue;
+
+ nir_const_value *val = nir_src_as_const_value(intrin->src[0]);
+ /* We've found a non-constant value. Bail. */
+ if (!val)
+ return -1;
+
+ if (count == -1)
+ count = val->i[0];
+
+ /* We've found contradictory set_vertex_count intrinsics.
+ * This can happen if there are early-returns in main() and
+ * different paths emit different numbers of vertices.
+ */
+ if (count != val->i[0])
+ return -1;
+ }
+ }
+ }
+
+ return count;
+}