agx: add SSA reindexing pass

spilling and SSA repair will generate piles of dead SSA defs. add a reindexing
pass to keep memory usag emanagable on large shaders.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28483>

src/asahi/compiler/agx_compiler.h

@@ -938,6 +938,7 @@ void agx_lower_uniform_sources(agx_context *ctx);
 void agx_opt_cse(agx_context *ctx);
 void agx_dce(agx_context *ctx, bool partial);
 void agx_pressure_schedule(agx_context *ctx);
+void agx_reindex_ssa(agx_context *ctx);
 void agx_ra(agx_context *ctx);
 void agx_lower_64bit_postra(agx_context *ctx);
 void agx_insert_waits(agx_context *ctx);

src/asahi/compiler/agx_reindex_ssa.c

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2024 Valve Corporation
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <stdlib.h>
+#include "agx_compiler.h"
+
+/* Reindex SSA to reduce memory usage */
+
+void
+agx_reindex_ssa(agx_context *ctx)
+{
+   unsigned *remap = calloc(ctx->alloc, sizeof(*remap));
+
+   ctx->alloc = 0;
+
+   agx_foreach_instr_global(ctx, I) {
+      agx_foreach_ssa_dest(I, d) {
+         assert(!remap[I->dest[d].value] && "input is SSA");
+         remap[I->dest[d].value] = ctx->alloc++;
+         I->dest[d].value = remap[I->dest[d].value];
+      }
+   }
+
+   agx_foreach_instr_global(ctx, I) {
+      agx_foreach_ssa_src(I, s) {
+         I->src[s].value = remap[I->src[s].value];
+      }
+   }
+
+   free(remap);
+}

src/asahi/compiler/meson.build

@@ -34,6 +34,7 @@ libasahi_agx_files = files(
   'agx_opt_empty_else.c',
   'agx_opt_jmp_none.c',
   'agx_optimizer.c',
+  'agx_reindex_ssa.c',
   'agx_register_allocate.c',
   'agx_validate.c',
 )