C.BSTART

assembly

[
  "C.BSTART COND,  label",
  "C.BSTART DIRECT, label"
]

block

[]

catalog_indices

[
  54,
  55
]

catalog_records

[
  {
    "asm": "C.BSTART COND,  label",
    "constraints": [],
    "encoding": [
      {
        "index": 0,
        "mask": "0x000f",
        "match": "0x0004",
        "width_bits": 16
      }
    ],
    "encoding_kind": "C16",
    "fields": [
      {
        "name": "simm12",
        "pieces": [
          {
            "instruction_lsb": 4,
            "value_lsb": 0,
            "width": 12
          }
        ],
        "signedness": "signed",
        "width": 12
      }
    ],
    "form_id": "c_bstart_16_c4e238a9227a",
    "length_bits": 16,
    "mnemonic": "C.BSTART",
    "semantic_family": "CMD",
    "semantic_group": "Bundle Split",
    "semantic_handler": "ExecuteBundleStart",
    "semantic_summary": "Starts a compressed standard block with a PC-relative direct or conditional candidate target.",
    "status": "accepted"
  },
  {
    "asm": "C.BSTART DIRECT, label",
    "constraints": [],
    "encoding": [
      {
        "index": 0,
        "mask": "0x000f",
        "match": "0x0002",
        "width_bits": 16
      }
    ],
    "encoding_kind": "C16",
    "fields": [
      {
        "name": "simm12",
        "pieces": [
          {
            "instruction_lsb": 4,
            "value_lsb": 0,
            "width": 12
          }
        ],
        "signedness": "signed",
        "width": 12
      }
    ],
    "form_id": "c_bstart_16_f833d2a4753c",
    "length_bits": 16,
    "mnemonic": "C.BSTART",
    "semantic_family": "CMD",
    "semantic_group": "Bundle Split",
    "semantic_handler": "ExecuteBundleStart",
    "semantic_summary": "Starts a compressed standard block with a PC-relative direct or conditional candidate target.",
    "status": "accepted"
  }
]

classification

[
  "encoding"
]

contract

{
  "block_composition": [
    "After any active predecessor block commits successfully, C.BSTART opens one Standard block. Header commands execute sequentially until BSTOP or the next BSTART commits the new BARG continuation."
  ],
  "canonical_assembly": [
    "C.BSTART COND,  label",
    "C.BSTART DIRECT, label"
  ],
  "defaults": [
    "simm12 is always encoded. Encoded zero computes the candidate target P and is not omission.",
    "The conditional form initializes BARG.TAKEN to false; the direct form initializes it to true."
  ],
  "encoding_class": "standalone-encoded",
  "examples": [
    "C.BSTART DIRECT, label",
    "C.BSTART COND, label"
  ],
  "exceptions": [
    "An odd computed candidate target raises Fault_InstructionPC before predecessor retirement or new BARG effects.",
    "If predecessor commit fails, the retiring block remains authoritative and no Standard BARG is installed."
  ],
  "field_contracts": {},
  "field_zero_meanings": {
    "simm12": "Encoded zero supplies a zero displacement or zero immediate value."
  },
  "legality": [
    "Exactly the low-nibble forms 0x2 (DIRECT) and 0x4 (COND) are assigned to C.BSTART.",
    "simm12 accepts every signed 12-bit value and computes P + (SignExtend(simm12) << 1)."
  ],
  "memory_effects": [
    "none"
  ],
  "operands": [
    {
      "field": "simm12",
      "role": "12-bit signed bundle target displacement"
    }
  ],
  "ordering": [
    "Decode, target calculation, and target alignment checks precede predecessor retirement. New BARG state is installed only after successful retirement."
  ],
  "standalone_opcode": true,
  "state_effects": [
    "Installs BARG.BPC=P, BlockType=STD, BPCN=the computed candidate target, and TYPE=DIRECT or COND.",
    "DIRECT installs TAKEN=1; COND installs TAKEN=0 until an applicable SETC operation resolves it. The candidate continuation is selected only at BSTOP or the next BSTART."
  ]
}

depends_on

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

id

PTO-BLOCK-C-BSTART

mnemonic

C.BSTART

summary

Starts a compressed standard block with a PC-relative direct or conditional candidate target.

surface

block

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