mesa/src/asahi/compiler/agx_validate.c

/*
 * Copyright 2022 Alyssa Rosenzweig
 * Copyright 2021 Collabora, Ltd.
 * SPDX-License-Identifier: MIT
 */

#include "agx_compiler.h"
#include "agx_debug.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_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:
      case AGX_OPCODE_STOP:
         agx_validate_assert(state == AGX_BLOCK_STATE_CF);
         break;
      }
   }

   return true;
}

static bool
agx_validate_sources(agx_instr *I)
{
   agx_foreach_src(I, s) {
      agx_index src = I->src[s];

      if (src.type == AGX_INDEX_IMMEDIATE) {
         agx_validate_assert(!src.kill);
         agx_validate_assert(!src.cache);
         agx_validate_assert(!src.discard);

         bool ldst = agx_allows_16bit_immediate(I);

         /* Immediates are encoded as 8-bit (16-bit for memory load/store). For
          * integers, they extend to 16-bit. For floating point, they are 8-bit
          * minifloats. The 8-bit minifloats are a strict subset of 16-bit
          * standard floats, so we treat them as such in the IR, with an
          * implicit f16->f32 for 32-bit floating point operations.
          */
         agx_validate_assert(src.size == AGX_SIZE_16);
         agx_validate_assert(src.value < (1 << (ldst ? 16 : 8)));
      } else if (I->op == AGX_OPCODE_COLLECT && !agx_is_null(src)) {
         agx_validate_assert(src.size == I->src[0].size);
      }
   }

   return true;
}

static bool
agx_validate_defs(agx_instr *I, BITSET_WORD *defs)
{
   agx_foreach_ssa_src(I, s) {
      /* Skip phis, they're special in loop headers */
      if (I->op == AGX_OPCODE_PHI)
         break;

      /* Sources must be defined before their use */
      if (!BITSET_TEST(defs, I->src[s].value))
         return false;
   }

   agx_foreach_ssa_dest(I, d) {
      /* Static single assignment */
      if (BITSET_TEST(defs, I->dest[d].value))
         return false;

      BITSET_SET(defs, I->dest[d].value);
   }

   return true;
}

/*
 * Type check the dimensionality of sources and destinations. This occurs in two
 * passes, first to gather all destination sizes, second to validate all source
 * sizes. Depends on SSA form.
 */
static bool
agx_validate_width(agx_context *ctx)
{
   bool succ = true;
   uint8_t *width = calloc(ctx->alloc, sizeof(uint8_t));

   agx_foreach_instr_global(ctx, I) {
      agx_foreach_dest(I, d) {
         if (I->dest[d].type != AGX_INDEX_NORMAL)
            continue;

         unsigned v = I->dest[d].value;
         assert(width[v] == 0 && "broken SSA");

         width[v] = agx_write_registers(I, d);
      }
   }

   agx_foreach_instr_global(ctx, I) {
      agx_foreach_ssa_src(I, s) {
         unsigned v = I->src[s].value;
         unsigned n = agx_read_registers(I, s);

         if (width[v] != n) {
            succ = false;
            fprintf(stderr, "source %u, expected width %u, got width %u\n", s,
                    n, width[v]);
            agx_print_instr(I, stderr);
            fprintf(stderr, "\n");
         }
      }
   }

   free(width);
   return succ;
}

static bool
agx_validate_predecessors(agx_block *block)
{
   /* Loop headers (only) have predecessors that are later in source form */
   bool has_later_preds = false;

   agx_foreach_predecessor(block, pred) {
      if ((*pred)->index >= block->index)
         has_later_preds = true;
   }

   if (block->loop_header != has_later_preds)
      return false;

   /* Successors and predecessors are found together */
   agx_foreach_predecessor(block, pred) {
      bool found = false;

      agx_foreach_successor((*pred), succ) {
         if (succ == block)
            found = true;
      }

      if (!found)
         return false;
   }

   return true;
}

void
agx_validate(agx_context *ctx, const char *after)
{
   bool fail = false;

   if (agx_compiler_debug & AGX_DBG_NOVALIDATE)
      return;

   int last_index = -1;

   agx_foreach_block(ctx, block) {
      if ((int)block->index < last_index) {
         fprintf(stderr, "Out-of-order block index %d vs %d after %s\n",
                 block->index, last_index, after);
         agx_print_block(block, stdout);
         fail = true;
      }

      last_index = block->index;

      if (!agx_validate_block_form(block)) {
         fprintf(stderr, "Invalid block form after %s\n", after);
         agx_print_block(block, stdout);
         fail = true;
      }

      if (!agx_validate_predecessors(block)) {
         fprintf(stderr, "Invalid loop header flag after %s\n", after);
         agx_print_block(block, stdout);
         fail = true;
      }
   }

   {
      BITSET_WORD *defs = calloc(sizeof(BITSET_WORD), BITSET_WORDS(ctx->alloc));

      agx_foreach_instr_global(ctx, I) {
         if (!agx_validate_defs(I, defs)) {
            fprintf(stderr, "Invalid defs after %s\n", after);
            agx_print_instr(I, stdout);
            fail = true;
         }
      }

      free(defs);
   }

   agx_foreach_instr_global(ctx, I) {
      if (!agx_validate_sources(I)) {
         fprintf(stderr, "Invalid sources form after %s\n", after);
         agx_print_instr(I, stdout);
         fail = true;
      }
   }

   if (!agx_validate_width(ctx)) {
      fprintf(stderr, "Invalid vectors after %s\n", after);
      fail = true;
   }

   /* TODO: Validate more invariants */

   if (fail) {
      agx_print_shader(ctx, stderr);
      exit(1);
   }
}

#endif /* NDEBUG */