Mesa (master): nir: Add a nir_opt_undef() to handle csels with undef.
Eric Anholt
anholt at kemper.freedesktop.org
Fri Aug 14 18:41:52 UTC 2015
Module: Mesa
Branch: master
Commit: 9e6dc5b64d5e931c7ebc272096eccab102b75d76
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=9e6dc5b64d5e931c7ebc272096eccab102b75d76
Author: Eric Anholt <eric at anholt.net>
Date: Tue Aug 4 16:25:24 2015 -0700
nir: Add a nir_opt_undef() to handle csels with undef.
We may find a cause to do more undef optimization in the future, but for
now this fixes up things after if flattening. vc4 was handling this
internally most of the time, but a GLB2.7 shader that did a conditional
discard and assign gl_FragColor in the else was still emitting some extra
code.
total instructions in shared programs: 100809 -> 100795 (-0.01%)
instructions in affected programs: 37 -> 23 (-37.84%)
v2: Use nir_instr_rewrite_src() to update def/use on src[0] (by Thomas
Helland).
v3: Make sure to flag metadata dirties, and copy the swizzle and abs/neg
over to src[0], too (by anholt).
Reviewed-by: Thomas Helland <thomashelland90 at gmail.com> (v2)
Tested-by: Thomas Helland <thomashelland90 at gmail.com> (v2)
---
src/gallium/drivers/vc4/vc4_program.c | 1 +
src/glsl/Makefile.sources | 1 +
src/glsl/nir/nir.h | 2 +
src/glsl/nir/nir_opt_undef.c | 104 +++++++++++++++++++++++++++++++++
4 files changed, 108 insertions(+)
diff --git a/src/gallium/drivers/vc4/vc4_program.c b/src/gallium/drivers/vc4/vc4_program.c
index e9120b7..4a3a277 100644
--- a/src/gallium/drivers/vc4/vc4_program.c
+++ b/src/gallium/drivers/vc4/vc4_program.c
@@ -1627,6 +1627,7 @@ vc4_optimize_nir(struct nir_shader *s)
progress = nir_opt_peephole_select(s) || progress;
progress = nir_opt_algebraic(s) || progress;
progress = nir_opt_constant_folding(s) || progress;
+ progress = nir_opt_undef(s) || progress;
} while (progress);
}
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index a0e85ed..0b77244 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -56,6 +56,7 @@ NIR_FILES = \
nir/nir_opt_peephole_ffma.c \
nir/nir_opt_peephole_select.c \
nir/nir_opt_remove_phis.c \
+ nir/nir_opt_undef.c \
nir/nir_print.c \
nir/nir_remove_dead_variables.c \
nir/nir_search.c \
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 9aae6d7..222a219 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1704,6 +1704,8 @@ bool nir_opt_peephole_ffma(nir_shader *shader);
bool nir_opt_remove_phis(nir_shader *shader);
+bool nir_opt_undef(nir_shader *shader);
+
void nir_sweep(nir_shader *shader);
#ifdef __cplusplus
diff --git a/src/glsl/nir/nir_opt_undef.c b/src/glsl/nir/nir_opt_undef.c
new file mode 100644
index 0000000..4ab27a8
--- /dev/null
+++ b/src/glsl/nir/nir_opt_undef.c
@@ -0,0 +1,104 @@
+/*
+ * Copyright © 2015 Broadcom
+ *
+ * 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"
+
+/** @file nir_opt_undef.c
+ *
+ * Handles optimization of operations involving ssa_undef. For now, we just
+ * make sure that csels between undef and some other value just give the other
+ * value (on the assumption that the condition's going to be choosing the
+ * defined value). This reduces work after if flattening when each side of
+ * the if is defining a variable.
+ *
+ * Some day, we may find some use for making other operations consuming an
+ * undef arg output undef, but I don't know of any cases currently.
+ */
+
+static bool
+opt_undef_alu(nir_alu_instr *instr)
+{
+ if (instr->op != nir_op_bcsel && instr->op != nir_op_fcsel)
+ return false;
+
+ assert(instr->dest.dest.is_ssa);
+
+ for (int i = 1; i <= 2; i++) {
+ if (!instr->src[i].src.is_ssa)
+ continue;
+
+ nir_instr *parent = instr->src[i].src.ssa->parent_instr;
+ if (parent->type != nir_instr_type_ssa_undef)
+ continue;
+
+ /* We can't just use nir_alu_src_copy, because we need the def/use
+ * updated.
+ */
+ nir_instr_rewrite_src(&instr->instr, &instr->src[0].src,
+ instr->src[i == 1 ? 2 : 1].src);
+ nir_alu_src_copy(&instr->src[0], &instr->src[i == 1 ? 2 : 1],
+ ralloc_parent(instr));
+
+ nir_src empty_src;
+ memset(&empty_src, 0, sizeof(empty_src));
+ nir_instr_rewrite_src(&instr->instr, &instr->src[1].src, empty_src);
+ nir_instr_rewrite_src(&instr->instr, &instr->src[2].src, empty_src);
+ instr->op = nir_op_imov;
+
+ return true;
+ }
+
+ return false;
+}
+
+static bool
+opt_undef_block(nir_block *block, void *data)
+{
+ bool *progress = data;
+
+ nir_foreach_instr_safe(block, instr) {
+ if (instr->type == nir_instr_type_alu)
+ if (opt_undef_alu(nir_instr_as_alu(instr)))
+ (*progress) = true;
+ }
+
+ return true;
+}
+
+bool
+nir_opt_undef(nir_shader *shader)
+{
+ bool progress = false;
+
+ nir_foreach_overload(shader, overload) {
+ if (overload->impl) {
+ nir_foreach_block(overload->impl, opt_undef_block, &progress);
+ if (progress)
+ nir_metadata_preserve(overload->impl,
+ nir_metadata_block_index |
+ nir_metadata_dominance);
+ }
+ }
+
+ return progress;
+}
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