agx: Add validation pass

For now, just check that we didn't botch the structure of the block,
since this just bit me.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16268>

src/asahi/compiler/agx_compile.c

@@ -38,6 +38,7 @@ static const struct debug_named_value agx_debug_options[] = {
    {"shaderdb",  AGX_DBG_SHADERDB,	"Print statistics"},
    {"verbose",   AGX_DBG_VERBOSE,	"Disassemble verbosely"},
    {"internal",  AGX_DBG_INTERNAL,	"Dump even internal shaders"},
+   {"novalidate",AGX_DBG_NOVALIDATE,"Skip IR validation in debug builds"},
    DEBUG_NAMED_VALUE_END
 };
 
@@ -1790,11 +1791,14 @@ agx_compile_shader_nir(nir_shader *nir,
    agx_foreach_block(ctx, block)
       block->index = ctx->num_blocks++;
 
+   agx_validate(ctx, "IR translation");
+
    if (agx_debug & AGX_DBG_SHADERS && !skip_internal)
       agx_print_shader(ctx, stdout);
 
    agx_optimizer(ctx);
    agx_dce(ctx);
+   agx_validate(ctx, "Optimization");
 
    if (agx_debug & AGX_DBG_SHADERS && !skip_internal)
       agx_print_shader(ctx, stdout);

src/asahi/compiler/agx_compiler.h

@@ -44,6 +44,7 @@ enum agx_dbg {
    AGX_DBG_SHADERDB    = BITFIELD_BIT(2),
    AGX_DBG_VERBOSE     = BITFIELD_BIT(3),
    AGX_DBG_INTERNAL    = BITFIELD_BIT(4),
+   AGX_DBG_NOVALIDATE  = BITFIELD_BIT(5),
 };
 
 extern int agx_debug;
@@ -735,6 +736,12 @@ void agx_dce(agx_context *ctx);
 void agx_ra(agx_context *ctx);
 void agx_pack_binary(agx_context *ctx, struct util_dynarray *emission);
 
+#ifndef NDEBUG
+void agx_validate(agx_context *ctx, const char *after_str);
+#else
+static inline void agx_validate(UNUSED agx_context *ctx, UNUSED const char *after_str) { return; }
+#endif
+
 unsigned agx_write_registers(agx_instr *I, unsigned d);
 
 struct agx_copy {

src/asahi/compiler/agx_validate.c

@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2022 Alyssa Rosenzweig
+ * 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 MERCHANTAagxLITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIAagxLITY, 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 "agx_compiler.h"
+
+/* Validatation doesn't make sense in release builds */
+#ifndef NDEBUG
+
+#define agx_validate_assert(stmt) if (!(stmt)) { return false; }
+
+/*
+ * If a block contains phi nodes, they must come at the start of the block. If a
+ * block contains control flow, it must come after a p_logical_end marker.
+ * Therefore the form of a valid block is:
+ *
+ *       Phi nodes
+ *       General instructions
+ *       Logical end
+ *       Control flow instructions
+ *
+ * Validate that this form is satisfied.
+ *
+ * XXX: This only applies before we delete the logical end instructions, maybe
+ * that should be deferred though?
+ */
+enum agx_block_state {
+   AGX_BLOCK_STATE_PHI = 0,
+   AGX_BLOCK_STATE_BODY = 1,
+   AGX_BLOCK_STATE_CF = 2
+};
+
+static bool
+agx_validate_block_form(agx_block *block)
+{
+   enum agx_block_state state = AGX_BLOCK_STATE_PHI;
+
+   agx_foreach_instr_in_block(block, I) {
+      switch (I->op) {
+      case AGX_OPCODE_PHI:
+         agx_validate_assert(state == AGX_BLOCK_STATE_PHI);
+         break;
+
+      default:
+         agx_validate_assert(state != AGX_BLOCK_STATE_CF);
+         state = AGX_BLOCK_STATE_BODY;
+         break;
+
+      case AGX_OPCODE_P_LOGICAL_END:
+         agx_validate_assert(state != AGX_BLOCK_STATE_CF);
+         state = AGX_BLOCK_STATE_CF;
+         break;
+
+      case AGX_OPCODE_JMP_EXEC_ANY:
+      case AGX_OPCODE_JMP_EXEC_NONE:
+      case AGX_OPCODE_POP_EXEC:
+      case AGX_OPCODE_IF_ICMP:
+      case AGX_OPCODE_ELSE_ICMP:
+      case AGX_OPCODE_WHILE_ICMP:
+      case AGX_OPCODE_IF_FCMP:
+      case AGX_OPCODE_ELSE_FCMP:
+      case AGX_OPCODE_WHILE_FCMP:
+         agx_validate_assert(state == AGX_BLOCK_STATE_CF);
+         break;
+      }
+   }
+
+   return true;
+}
+
+void
+agx_validate(agx_context *ctx, const char *after)
+{
+   bool fail = false;
+
+   if (agx_debug & AGX_DBG_NOVALIDATE)
+      return;
+
+   agx_foreach_block(ctx, block) {
+      if (!agx_validate_block_form(block)) {
+         fprintf(stderr, "Invalid block form after %s\n", after);
+         agx_print_block(block, stdout);
+         fail = true;
+      }
+   }
+
+   /* TODO: Validate more invariants */
+
+   if (fail) {
+      agx_print_shader(ctx, stderr);
+      exit(1);
+   }
+}
+
+#endif /* NDEBUG */

src/asahi/compiler/meson.build

@@ -30,6 +30,7 @@ libasahi_agx_files = files(
   'agx_optimizer.c',
   'agx_register_allocate.c',
   'agx_uniforms.c',
+  'agx_validate.c',
 )
 
 agx_opcodes_h = custom_target(