BSTART.CALL

assembly

[
  "BSTART.CALL <br_label>, <rt_label>, ->ra"
]

block

[]

catalog_indices

[
  15
]

catalog_records

[
  {
    "asm": "BSTART.CALL <br_label>, <rt_label>, ->ra",
    "constraints": [],
    "encoding": [
      {
        "index": 0,
        "mask": "0xf83f000f",
        "match": "0x50160002",
        "width_bits": 32
      }
    ],
    "encoding_kind": "L32",
    "fields": [
      {
        "name": "simm12",
        "pieces": [
          {
            "instruction_lsb": 4,
            "value_lsb": 0,
            "width": 12
          }
        ],
        "signedness": "signed",
        "width": 12
      },
      {
        "name": "uimm5",
        "pieces": [
          {
            "instruction_lsb": 22,
            "value_lsb": 0,
            "width": 5
          }
        ],
        "signedness": "unsigned",
        "width": 5
      }
    ],
    "form_id": "bstart_call_32_9404418d1ae5",
    "length_bits": 32,
    "mnemonic": "BSTART.CALL",
    "semantic_family": "BBD",
    "semantic_group": "BSTART",
    "semantic_handler": "ExecuteBundleStart",
    "semantic_summary": "Atomically retires the old block, installs a direct-call BARG, and writes the independent return target to ra.",
    "status": "accepted"
  }
]

classification

[
  "execution"
]

contract

{
  "block_composition": [
    "none"
  ],
  "canonical_assembly": [
    "BSTART.CALL <br_label>, <rt_label>, ->ra"
  ],
  "defaults": [
    "simm12 and uimm5 are both present; encoded zero is a real zero displacement for that field."
  ],
  "encoding_class": "standalone-encoded",
  "examples": [
    "BSTART.CALL <br_label>, <rt_label>, ->ra"
  ],
  "exceptions": [
    "An odd call target raises Fault_InstructionPC before retiring-block effects.",
    "Decode, applicability, target, or retiring-commit failure preserves ra and the retiring BARG and installs no candidate BARG."
  ],
  "field_contracts": {},
  "field_zero_meanings": {
    "simm12": "Encoded zero supplies a zero displacement or zero immediate value.",
    "uimm5": "Encoded zero supplies a zero displacement or zero immediate value."
  },
  "legality": [
    "All bit patterns not excluded by the form decode are assigned by this instruction contract."
  ],
  "memory_effects": [
    "Any memory effects of the retiring block complete before the call BARG and ra are published; BSTART.CALL itself performs no memory access."
  ],
  "operands": [
    {
      "field": "simm12",
      "role": "12-bit signed bundle target displacement"
    },
    {
      "field": "uimm5",
      "role": "unsigned return-address displacement"
    }
  ],
  "ordering": [
    "Validate both targets, successfully commit the retiring block, then atomically install the new STD BARG and write ra."
  ],
  "standalone_opcode": true,
  "state_effects": [
    "Installs BARG.BPC=P, BlockType=STD, BPCN=call_target, TYPE=DIRECT, TAKEN=1, and writes return_target to ra.",
    "The call target is selected only when the new block later commits."
  ]
}

depends_on

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

id

PTO-BLOCK-BSTART-CALL

mnemonic

BSTART.CALL

summary

Atomically retires the old block, installs a direct-call BARG, and writes the independent return target to ra.

surface

block

{
  "classification": [
    "execution"
  ],
  "documentation": "docs/block/execution/BSTART.CALL.md",
  "id": "PTO-BLOCK-BSTART-CALL",
  "instruction_contract": {
    "artifact": "spec/evidence/instruction-contract-closure.json",
    "mnemonic": "BSTART.CALL",
    "ndf_clause": "PTO-INST-BLOCK-BSTART-CALL"
  },
  "mnemonic": "BSTART.CALL",
  "readiness_subjects": [
    "ADR-0032",
    "ADR-0052",
    "ADR-0055",
    "ADR-0059",
    "ADR-0077"
  ],
  "semantic_tests": [
    "PTO-AVS-BLOCK-BSTART-CALL-ATOMIC-001",
    "PTO-AVS-BLOCK-BSTART-CALL-FUSED-FORMS-001",
    "PTO-AVS-BLOCK-BSTART-CALL-ROLLBACK-001"
  ],
  "source": "asl/block/execution/BSTART.CALL.asl",
  "surface": "block",
  "tests": [
    "PTO-AVS-BLOCK-BSTART-CALL-ATOMIC-001",
    "PTO-AVS-BLOCK-BSTART-CALL-DECODE-001",
    "PTO-AVS-BLOCK-BSTART-CALL-FUSED-FORMS-001",
    "PTO-AVS-BLOCK-BSTART-CALL-ROLLBACK-001"
  ]
}