Mesa (master): ir3/nir: Add new NIR AlgebraicPass for lowering imul

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Module: Mesa
Branch: master
Commit: 340277ad719526cd4c02583a08151473cc0a6904
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=340277ad719526cd4c02583a08151473cc0a6904

Author: Eduardo Lima Mitev <elima at igalia.com>
Date:   Mon May 13 00:23:58 2019 +0200

ir3/nir: Add new NIR AlgebraicPass for lowering imul

Currently, ir3 backend compiler is lowering integer multiplication from:

dst = a * b

to:

dst = (al * bl) + (ah * bl << 16) + (al * bh << 16)

by emitting this code:

mull.u tmp0, a, b           ; mul low, i.e. al * bl
madsh.m16 tmp1, a, b, tmp0  ; mul-add shift high mix, i.e. ah * bl << 16
madsh.m16 dst, b, a, tmp1   ; i.e. al * bh << 16

which at that point has very low chances of being optimized.

This patch adds a new nir_algebraic.AlgebraicPass to performs this
lowering during NIR algebraic optimization passes, giving it a better
chance for optimizing the resulting code.

Reviewed-by: Eric Anholt <eric at anholt.net>

---

 src/freedreno/ir3/ir3_nir.h       |  1 +
 src/freedreno/ir3/ir3_nir_imul.py | 50 +++++++++++++++++++++++++++++++++++++++
 src/freedreno/ir3/meson.build     | 14 ++++++++++-
 3 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/src/freedreno/ir3/ir3_nir.h b/src/freedreno/ir3/ir3_nir.h
index 84c09b073f0..6314c097956 100644
--- a/src/freedreno/ir3/ir3_nir.h
+++ b/src/freedreno/ir3/ir3_nir.h
@@ -34,6 +34,7 @@
 #include "ir3_shader.h"
 
 bool ir3_nir_apply_trig_workarounds(nir_shader *shader);
+bool ir3_nir_lower_imul(nir_shader *shader);
 bool ir3_nir_lower_tg4_to_tex(nir_shader *shader);
 bool ir3_nir_lower_io_offsets(nir_shader *shader);
 bool ir3_nir_lower_load_barycentric_at_sample(nir_shader *shader);
diff --git a/src/freedreno/ir3/ir3_nir_imul.py b/src/freedreno/ir3/ir3_nir_imul.py
new file mode 100644
index 00000000000..f648cd11071
--- /dev/null
+++ b/src/freedreno/ir3/ir3_nir_imul.py
@@ -0,0 +1,50 @@
+#
+# Copyright (C) 2019 Igalia S.L.
+#
+# 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.
+
+from __future__ import print_function
+
+import argparse
+import sys
+
+imul_lowering = [
+	(('imul', 'a at 32', 'b at 32'), ('imadsh_mix16', 'b', 'a', ('imadsh_mix16', 'a', 'b', ('umul_low', 'a', 'b')))),
+]
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-p', '--import-path', required=True)
+    args = parser.parse_args()
+    sys.path.insert(0, args.import_path)
+    run()
+
+
+def run():
+    import nir_algebraic  # pylint: disable=import-error
+
+    print('#include "ir3_nir.h"')
+    print(nir_algebraic.AlgebraicPass("ir3_nir_lower_imul",
+                                      imul_lowering).render())
+
+
+if __name__ == '__main__':
+    main()
diff --git a/src/freedreno/ir3/meson.build b/src/freedreno/ir3/meson.build
index bf4d41b5444..be03ffb88c3 100644
--- a/src/freedreno/ir3/meson.build
+++ b/src/freedreno/ir3/meson.build
@@ -30,6 +30,18 @@ ir3_nir_trig_c = custom_target(
   depend_files : nir_algebraic_py,
 )
 
+ir3_nir_imul_c = custom_target(
+  'ir3_nir_imul.c',
+  input : 'ir3_nir_imul.py',
+  output : 'ir3_nir_imul.c',
+  command : [
+    prog_python, '@INPUT@',
+    '-p', join_paths(meson.source_root(), 'src/compiler/nir/'),
+  ],
+  capture : true,
+  depend_files : nir_algebraic_py,
+)
+
 libfreedreno_ir3_files = files(
   'disasm-a3xx.c',
   'instr-a3xx.h',
@@ -66,7 +78,7 @@ libfreedreno_ir3_files = files(
 
 libfreedreno_ir3 = static_library(
   'freedreno_ir3',
-  [libfreedreno_ir3_files, ir3_nir_trig_c],
+  [libfreedreno_ir3_files, ir3_nir_trig_c, ir3_nir_imul_c],
   include_directories : [inc_freedreno, inc_common],
   c_args : [c_vis_args, no_override_init_args],
   cpp_args : [cpp_vis_args],