pan/va: Lower split 64-bit sources

This ensures Valhall 64-bit constraints are respected in a simple way. It's not
the most efficient, though. Optimization is deferred until full Valhall support
is upstreamed and the RA is overhauled.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16585>

src/panfrost/bifrost/bi_ra.c

@@ -567,6 +567,9 @@ bi_register_allocate(bi_context *ctx)
         /* Number of bytes of memory we've spilled into */
         unsigned spill_count = ctx->info.tls_size;
 
+        if (ctx->arch >= 9)
+                va_lower_split_64bit(ctx);
+
         /* Try with reduced register pressure to improve thread count */
         if (ctx->arch >= 7) {
                 bi_invalidate_liveness(ctx);

src/panfrost/bifrost/compiler.h

@@ -1049,6 +1049,7 @@ void bi_lower_fau(bi_context *ctx);
 void bi_assign_scoreboard(bi_context *ctx);
 void bi_register_allocate(bi_context *ctx);
 void va_optimize(bi_context *ctx);
+void va_lower_split_64bit(bi_context *ctx);
 
 void bi_lower_opt_instruction(bi_instr *I);
 

src/panfrost/bifrost/meson.build

@@ -47,6 +47,7 @@ libpanfrost_bifrost_files = files(
   'bifrost_compile.c',
   'valhall/va_lower_constants.c',
   'valhall/va_lower_isel.c',
+  'valhall/va_lower_split_64bit.c',
   'valhall/va_optimize.c',
   'valhall/va_pack.c',
   'valhall/va_perf.c',

src/panfrost/bifrost/valhall/va_lower_split_64bit.c

@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+#include "va_compiler.h"
+#include "bi_builder.h"
+
+/*
+ * Bifrost uses split 64-bit addresses, specified as two consecutive sources.
+ * Valhall uses contiguous 64-bit addresses, specified as a single source with
+ * an aligned register pair. This simple pass inserts moves to lower split
+ * 64-bit sources into a collect, ensuring the register constraints will be
+ * respected by RA. This could be optimized, but this is deferred for now.
+ */
+static void
+lower_split_src(bi_context *ctx, bi_instr *I, unsigned s)
+{
+   /* Fix up for mismatch between IR and Valhall BLEND */
+   if (I->op == BI_OPCODE_BLEND) {
+      assert(s == 1);
+      s = 2;
+   }
+
+   /* Skip sources that are already split properly */
+   bi_index offset_fau = I->src[s];
+   offset_fau.offset++;
+
+   if (I->src[s].type == BI_INDEX_FAU &&
+       I->src[s].offset == 0 &&
+       bi_is_value_equiv(offset_fau, I->src[s + 1])) {
+      return;
+   }
+
+   /* Allocate temporary before the instruction */
+   bi_builder b = bi_init_builder(ctx, bi_before_instr(I));
+   bi_index collect = bi_temp(ctx);
+
+   /* Emit collect */
+   for (unsigned w = 0; w < 2; ++w) {
+      bi_mov_i32_to(&b, bi_word(collect, w), I->src[s + w]);
+      I->src[s + w] = bi_word(collect, w);
+   }
+}
+
+void
+va_lower_split_64bit(bi_context *ctx)
+{
+   bi_foreach_instr_global(ctx, I) {
+      bi_foreach_src(I, s) {
+         if (bi_is_null(I->src[s]))
+            continue;
+
+         struct va_src_info info = va_src_info(I->op, s);
+
+         if (info.size == VA_SIZE_64)
+            lower_split_src(ctx, I, s);
+      }
+   }
+}