pan/midgard: Add imov->fmov optimization

When moving constants, if switching to a floating-point representation
doesn't break anything, we'd rather have an fmov than an imov,
permitting inlining the constant in many circumstances.

total quadwords in shared programs: 3408 -> 3366 (-1.23%)
quadwords in affected programs: 1188 -> 1146 (-3.54%)
helped: 41
HURT: 0
helped stats (abs) min: 1 max: 2 x̄: 1.02 x̃: 1
helped stats (rel) min: 0.19% max: 25.00% x̄: 9.65% x̃: 11.11%
95% mean confidence interval for quadwords value: -1.07 -0.98
95% mean confidence interval for quadwords %-change: -11.38% -7.93%
Quadwords are helped.

Signed-off-by: Alyssa Rosenzweig <[email protected]>

4 files changed, 85 insertions, 0 deletions

diff --git a/src/panfrost/midgard/compiler.h b/src/panfrost/midgard/compiler.h
index a64bb55203d..8bea56548ae 100644
--- a/src/panfrost/midgard/compiler.h
+++ b/src/panfrost/midgard/compiler.h
@@ -640,5 +640,6 @@ void midgard_lower_invert(compiler_context *ctx, midgard_block *block);
 bool midgard_opt_not_propagate(compiler_context *ctx, midgard_block *block);
 bool midgard_opt_fuse_src_invert(compiler_context *ctx, midgard_block *block);
 bool midgard_opt_fuse_dest_invert(compiler_context *ctx, midgard_block *block);
+bool midgard_opt_promote_fmov(compiler_context *ctx, midgard_block *block);
 
 #endif
diff --git a/src/panfrost/midgard/meson.build b/src/panfrost/midgard/meson.build
index 8da5184e871..704d847cb4f 100644
--- a/src/panfrost/midgard/meson.build
+++ b/src/panfrost/midgard/meson.build
@@ -34,6 +34,7 @@ libpanfrost_midgard_files = files(
   'midgard_opt_copy_prop.c',
   'midgard_opt_dce.c',
   'midgard_opt_invert.c',
+  'midgard_opt_float.c',
   'midgard_opt_perspective.c',
   'cppwrap.cpp',
   'disassemble.c',
diff --git a/src/panfrost/midgard/midgard_compile.c b/src/panfrost/midgard/midgard_compile.c
index be4318d371a..816adb7fd38 100644
--- a/src/panfrost/midgard/midgard_compile.c
+++ b/src/panfrost/midgard/midgard_compile.c
@@ -2305,6 +2305,7 @@ emit_block(compiler_context *ctx, nir_block *block)
         }
 
         inline_alu_constants(ctx);
+        midgard_opt_promote_fmov(ctx, ctx->current_block);
         embedded_to_inline_constant(ctx);
 
         /* Append fragment shader epilogue (value writeout) */
diff --git a/src/panfrost/midgard/midgard_opt_float.c b/src/panfrost/midgard/midgard_opt_float.c
new file mode 100644
index 00000000000..630620120e3
--- /dev/null
+++ b/src/panfrost/midgard/midgard_opt_float.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2019 Collabora, Ltd.
+ *
+ * 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.
+ *
+ * Authors (Collabora):
+ *    Alyssa Rosenzweig <[email protected]>
+ */
+
+#include "compiler.h"
+#include "midgard_ops.h"
+#include <math.h>
+
+/* Could a 32-bit value represent exactly a 32-bit floating point? */
+
+static bool
+mir_constant_float(uint32_t u)
+{
+        /* Cast */
+        float f = 0;
+        memcpy(&f, &u, sizeof(u));
+
+        /* TODO: What exactly is the condition? */
+        return !(isnan(f) || isinf(f));
+}
+
+/* Promotes imov with a constant to fmov where the constant is exactly
+ * representible as a float */
+
+bool
+midgard_opt_promote_fmov(compiler_context *ctx, midgard_block *block)
+{
+        bool progress = false;
+
+        mir_foreach_instr_in_block(block, ins) {
+                if (ins->type != TAG_ALU_4) continue;
+                if (ins->alu.op != midgard_alu_op_imov) continue;
+                if (ins->ssa_args.inline_constant) continue;
+                if (!ins->has_constants) continue;
+                if (mir_nontrivial_source2_mod_simple(ins)) continue;
+                if (mir_nontrivial_outmod(ins)) continue;
+
+                /* We found an imov with a constant. Check the constants */
+                bool ok = true;
+
+                for (unsigned i = 0; i < ARRAY_SIZE(ins->constants); ++i)
+                        ok &= mir_constant_float(ins->constants[i]);
+
+                if (!ok)
+                        continue;
+
+                /* Rewrite to fmov */
+                ins->alu.op = midgard_alu_op_fmov;
+                ins->alu.outmod = 0;
+
+                /* Clear the int mod */
+                midgard_vector_alu_src u = vector_alu_from_unsigned(ins->alu.src2);
+                u.mod = 0;
+                ins->alu.src2 = vector_alu_srco_unsigned(u);
+
+                progress |= true;
+        }
+
+        return progress;
+}