B.HINT

assembly

[
  "B.HINT {BR.{likely, unlikely}, TEMP.{hot, warm, cool, none}, PRFSIZE}",
  "B.HINT TRACE.{begin, end}"
]

block

[]

catalog_indices

[
  5,
  6
]

catalog_records

[
  {
    "asm": "B.HINT {BR.{likely, unlikely}, TEMP.{hot, warm, cool, none}, PRFSIZE}",
    "constraints": [],
    "encoding": [
      {
        "index": 0,
        "mask": "0x00087fff",
        "match": "0x00000033",
        "width_bits": 32
      }
    ],
    "encoding_kind": "L32",
    "fields": [
      {
        "name": "L/UL",
        "pieces": [
          {
            "instruction_lsb": 16,
            "value_lsb": 0,
            "width": 1
          }
        ],
        "signedness": "encoding-defined",
        "width": 1
      },
      {
        "name": "V",
        "pieces": [
          {
            "instruction_lsb": 15,
            "value_lsb": 0,
            "width": 1
          }
        ],
        "signedness": "encoding-defined",
        "width": 1
      },
      {
        "name": "prefetch_size",
        "pieces": [
          {
            "instruction_lsb": 20,
            "value_lsb": 0,
            "width": 12
          }
        ],
        "signedness": "encoding-defined",
        "width": 12
      },
      {
        "name": "temp",
        "pieces": [
          {
            "instruction_lsb": 17,
            "value_lsb": 0,
            "width": 2
          }
        ],
        "signedness": "encoding-defined",
        "width": 2
      }
    ],
    "form_id": "b_hint_32_69d942ff1583",
    "length_bits": 32,
    "mnemonic": "B.HINT",
    "semantic_family": "CMD",
    "semantic_group": "Bundle Hint",
    "semantic_handler": "SetBundleHint",
    "semantic_summary": "Records one optional per-block branch, temperature, prefetch-size, or trace-boundary hint without changing functional results.",
    "status": "accepted"
  },
  {
    "asm": "B.HINT TRACE.{begin, end}",
    "constraints": [],
    "encoding": [
      {
        "index": 0,
        "mask": "0xffff7fff",
        "match": "0x00001033",
        "width_bits": 32
      }
    ],
    "encoding_kind": "L32",
    "fields": [
      {
        "name": "B/E",
        "pieces": [
          {
            "instruction_lsb": 15,
            "value_lsb": 0,
            "width": 1
          }
        ],
        "signedness": "encoding-defined",
        "width": 1
      }
    ],
    "form_id": "b_hint_32_f7d01d734925",
    "length_bits": 32,
    "mnemonic": "B.HINT",
    "semantic_family": "CMD",
    "semantic_group": "Bundle Hint",
    "semantic_handler": "SetBundleHint",
    "semantic_summary": "Records one optional per-block branch, temperature, prefetch-size, or trace-boundary hint without changing functional results.",
    "status": "accepted"
  }
]

classification

[
  "lifecycle"
]

contract

{
  "block_composition": [
    "Ordinary form: optional once after BSTART and before the block body.",
    "TRACE form: acts as a block start and must later be terminated by BSTOP or the next BSTART."
  ],
  "canonical_assembly": [
    "B.HINT {BR.{likely, unlikely}, TEMP.{hot, warm, cool, none}, PRFSIZE}",
    "B.HINT TRACE.{begin, end}"
  ],
  "defaults": [
    "An ordinary block may omit B.HINT; omission supplies no branch, temperature, or prefetch guidance.",
    "For the ordinary form V=0 disables branch guidance, L/UL=0 denotes unlikely/fallthrough, temp=0 denotes none, and prefetch_size=0 requests no cache-line prefetch.",
    "For TRACE, B/E=0 denotes begin and B/E=1 denotes end."
  ],
  "encoding_class": "standalone-encoded",
  "examples": [
    "B.HINT {BR.likely, TEMP.hot, 64}",
    "B.HINT TRACE.begin"
  ],
  "exceptions": [
    "An ordinary B.HINT outside an active block header or a duplicate ordinary B.HINT raises Illegal Block Exception before hint state changes.",
    "If TRACE cannot retire an active predecessor block, the predecessor fault is preserved and the trace block is not opened."
  ],
  "field_contracts": {},
  "field_zero_meanings": {
    "V": "branch hint invalid; implementation predicts normally",
    "L/UL": "unlikely branch / likely fallthrough when V is one",
    "temp": "none",
    "prefetch_size": "no cache-line prefetch",
    "B/E": "TRACE.begin"
  },
  "legality": [
    "An ordinary B.HINT is legal only after BSTART and before the block body, and at most one B.HINT may belong to that block header.",
    "A second ordinary B.HINT raises Illegal Block Exception before replacing the first hint.",
    "B.HINT TRACE is a special block-start operation. It first retires any active predecessor block under the normal next-BSTART rule, then opens a new empty fallthrough block."
  ],
  "memory_effects": [
    "none"
  ],
  "operands": [
    {
      "field": "V",
      "role": "branch-hint validity: 0 invalid, 1 valid"
    },
    {
      "field": "L/UL",
      "role": "when V=1, 0 unlikely/fallthrough and 1 likely/taken"
    },
    {
      "field": "temp",
      "role": "temperature: 0 none, 1 cool, 2 warm, 3 hot"
    },
    {
      "field": "prefetch_size",
      "role": "number of cache lines to prefetch beginning with the cache line containing the current block instruction"
    },
    {
      "field": "B/E",
      "role": "trace boundary: 0 begin, 1 end"
    }
  ],
  "ordering": [
    "none"
  ],
  "standalone_opcode": true,
  "state_effects": [
    "Decode and retain the selected hint fields as pending state of the active block and increment the non-functional hint epoch.",
    "TRACE.begin or TRACE.end opens an empty block and records its boundary kind; it does not complete that block."
  ]
}

depends_on

[
  "PTO-BLOCK-MODEL-SCHEMA-PROFILE-ENCODING"
]

id

PTO-BLOCK-B-HINT

mnemonic

B.HINT

summary

Records one optional per-block branch, temperature, prefetch-size, or trace-boundary hint without changing functional results.

surface

block

{
  "classification": [
    "lifecycle"
  ],
  "documentation": "docs/block/lifecycle/B.HINT.md",
  "id": "PTO-BLOCK-B-HINT",
  "instruction_contract": {
    "artifact": "spec/evidence/instruction-contract-closure.json",
    "mnemonic": "B.HINT",
    "ndf_clause": "PTO-INST-BLOCK-B-HINT"
  },
  "mnemonic": "B.HINT",
  "readiness_subjects": [
    "ADR-0032",
    "ADR-0052",
    "ADR-0059",
    "ADR-0075"
  ],
  "semantic_tests": [
    "PTO-AVS-BLOCK-B-HINT-DUPLICATE-001",
    "PTO-AVS-BLOCK-B-HINT-FIELDS-001",
    "PTO-AVS-BLOCK-B-HINT-PLACEMENT-001",
    "PTO-AVS-BLOCK-B-HINT-TRACE-LIFECYCLE-001"
  ],
  "source": "asl/block/lifecycle/B.HINT.asl",
  "surface": "block",
  "tests": [
    "PTO-AVS-BLOCK-B-HINT-DECODE-001",
    "PTO-AVS-BLOCK-B-HINT-DUPLICATE-001",
    "PTO-AVS-BLOCK-B-HINT-FIELDS-001",
    "PTO-AVS-BLOCK-B-HINT-PLACEMENT-001",
    "PTO-AVS-BLOCK-B-HINT-TRACE-LIFECYCLE-001"
  ]
}