[RFC PATCH 17/17] eir: add peephole optimization

[Christian Gmeiner]

Some created shaders can contain instructions like:
  mov t0 t0

This simple pass removes that kind of mov instructions.

Signed-off-by: Christian Gmeiner <christian.gmeiner at gmail.com>
---
 src/etnaviv/compiler/eir_opt_peephole.c | 63 +++++++++++++++++++++++++
 src/etnaviv/compiler/eir_optimize.c     |  4 +-
 src/etnaviv/compiler/eir_optimize.h     |  5 ++
 src/etnaviv/compiler/meson.build        |  1 +
 4 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 src/etnaviv/compiler/eir_opt_peephole.c

diff --git a/src/etnaviv/compiler/eir_opt_peephole.c b/src/etnaviv/compiler/eir_opt_peephole.c
new file mode 100644
index 00000000000..a8cf848d652
--- /dev/null
+++ b/src/etnaviv/compiler/eir_opt_peephole.c
@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2019 Etnaviv Project
+ * Copyright (C) 2019 Zodiac Inflight Innovations
+ *
+ * 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, sub license,
+ * 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 NON-INFRINGEMENT. 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.
+ *
+ * Authors:
+ *    Christian Gmeiner <christian.gmeiner at gmail.com>
+ */
+
+#include "eir.h"
+#include "eir_optimize.h"
+
+static bool
+eir_opt_peephole_impl(struct eir_instruction *instr)
+{
+   /* remove "mov t0 t0" as seen with bin/gl-2.0-vertex-attr-0 */
+
+   if (instr->gc.opcode != GC_MOV)
+      return false;
+
+   if (instr->src[0].index != instr->dst.index)
+      return false;
+
+   if (instr->dst.writemask != (INST_COMPS_X | INST_COMPS_Y | INST_COMPS_Z | INST_COMPS_W))
+      return false;
+
+   if (instr->src[0].swizzle != INST_SWIZ_IDENTITY)
+      return false;
+
+   list_del(&instr->node);
+
+   return true;
+}
+
+bool
+eir_opt_peephole(struct eir *ir)
+{
+   bool progress = false;
+
+   eir_for_each_block(block, ir)
+      eir_for_each_inst_safe(inst, block)
+         progress |= eir_opt_peephole_impl(inst);
+
+   return progress;
+}
diff --git a/src/etnaviv/compiler/eir_optimize.c b/src/etnaviv/compiler/eir_optimize.c
index 6eae8e9c9ec..695ef76001a 100644
--- a/src/etnaviv/compiler/eir_optimize.c
+++ b/src/etnaviv/compiler/eir_optimize.c
@@ -44,5 +44,7 @@
 void
 eir_optimize(struct eir *ir)
 {
-   const bool print_opt_debug = true;
+   const bool print_opt_debug = false;
+
+   OPTPASS(eir_opt_peephole);
 }
diff --git a/src/etnaviv/compiler/eir_optimize.h b/src/etnaviv/compiler/eir_optimize.h
index b840a273c25..ecc9e44713c 100644
--- a/src/etnaviv/compiler/eir_optimize.h
+++ b/src/etnaviv/compiler/eir_optimize.h
@@ -28,4 +28,9 @@
 #ifndef H_EIR_OPTIMIZE
 #define H_EIR_OPTIMIZE
 
+struct eir;
+
+bool
+eir_opt_peephole(struct eir *ir);
+
 #endif // H_EIR_OPTIMIZE
diff --git a/src/etnaviv/compiler/meson.build b/src/etnaviv/compiler/meson.build
index 8343e6b91ad..f43e868208a 100644
--- a/src/etnaviv/compiler/meson.build
+++ b/src/etnaviv/compiler/meson.build
@@ -31,6 +31,7 @@ libetnaviv_compiler_files = files(
   'eir_nir_lower_alu_to_scalar.c',
   'eir_nir.c',
   'eir_nir.h',
+  'eir_opt_peephole.c',
   'eir_optimize.c',
   'eir_print.c',
   'eir_register_allocate.c',
-- 
2.21.0