LBU.PCR

assembly

[
  "lbu.pcr [symbol], ->{t, u, Rd}"
]

block

[]

catalog_indices

[
  312
]

catalog_records

[
  {
    "agu": {
      "action": "Load",
      "address_kind": "PCRelative",
      "offset_scale": 2,
      "prefetch_returns_address": false,
      "signed_load": false,
      "size_bytes": 1,
      "update_mode": "None"
    },
    "asm": "lbu.pcr [symbol], ->{t, u, Rd}",
    "constraints": [],
    "encoding": [
      {
        "index": 0,
        "mask": "0x0000707f",
        "match": "0x00004039",
        "width_bits": 32
      }
    ],
    "encoding_kind": "L32",
    "fields": [
      {
        "name": "RegDst",
        "pieces": [
          {
            "instruction_lsb": 7,
            "value_lsb": 0,
            "width": 5
          }
        ],
        "signedness": "encoding-defined",
        "width": 5
      },
      {
        "name": "simm17",
        "pieces": [
          {
            "instruction_lsb": 15,
            "value_lsb": 0,
            "width": 17
          }
        ],
        "signedness": "signed",
        "width": 17
      }
    ],
    "form_id": "lbu_pcr_32_5b571b0c8dc2",
    "length_bits": 32,
    "mnemonic": "LBU.PCR",
    "semantic_family": "AGU",
    "semantic_group": "LDA",
    "semantic_handler": "ExecuteScalarLoad",
    "semantic_summary": "LBU.PCR snapshots its scalar sources, forms its encoded address, and loads one aligned little-endian 1-byte value.",
    "status": "accepted"
  }
]

classification

[
  "agu"
]

contract

{
  "block_composition": [
    "none"
  ],
  "canonical_assembly": [
    "lbu.pcr [symbol], ->{t, u, Rd}"
  ],
  "defaults": [
    "Every displayed operand field is encoded explicitly; encoded zero is a value and never denotes omission."
  ],
  "encoding_class": "standalone-encoded",
  "examples": [
    "lbu.pcr [symbol], ->{t, u, Rd}"
  ],
  "exceptions": [
    "A fixed-bit mismatch, reserved field value, or unavailable selected T/U source raises Fault_IllegalInstruction before instruction effects.",
    "A misaligned 1-byte address raises Fault_DataAlignment before translation or permission. A later permission or bounded-memory failure raises Fault_DataPage at the original address.",
    "A fault emits no successful memory event, performs no partial memory or destination effect, preserves pending writeback, and leaves TPC at the faulting instruction.",
    "Recovery performs a full reissue: every address, source snapshot, preflight, memory operation, and destination is recomputed with no retained progress."
  ],
  "field_contracts": {},
  "field_zero_meanings": {
    "RegDst": "Encoded zero discards this result without suppressing the instruction's other effects.",
    "simm17": "Encoded zero supplies a zero displacement; it does not denote omission."
  },
  "legality": [
    "Every Reg5 destination is assigned: codes 1..23 write GPRs, code 30 pushes U, code 31 pushes T, and codes 0 and 24..29 discard only that result.",
    "simm17 assigns every signed 17-bit value -65536..65535; the encoded byte displacement is that value multiplied by 4.",
    "Each memory address must be aligned to the 1-byte access size; a 1-byte access is the complete transfer unit."
  ],
  "memory_effects": [
    "After complete preflight, perform one little-endian 1-byte load and record one relaxed load event.",
    "The load preserves memory and reservation state."
  ],
  "operands": [
    {
      "field": "RegDst",
      "role": "Reg5 loaded-value destination or discard"
    },
    {
      "field": "simm17",
      "role": "signed address displacement"
    }
  ],
  "ordering": [
    "Snapshot all explicit and implicit scalar sources before destination or memory effects; duplicate and source/destination aliases observe pre-instruction values.",
    "Complete the relaxed 1-byte memory operation, publish any result or writeback, and then advance TPC."
  ],
  "standalone_opcode": true,
  "state_effects": [
    "Clear TPC bits 1:0, sign-extend the encoded displacement, multiply it by four, and add it modulo 2^PTO_XLEN.",
    "After a successful 1-byte load, zero-extend the loaded value to PTO_XLEN and publish it through the destination.",
    "Successful execution advances TPC by 4 bytes; a rejected or faulting attempt does not retire."
  ]
}

depends_on

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

id

PTO-SCALAR-LBU-PCR

mnemonic

LBU.PCR

summary

LBU.PCR snapshots its scalar sources, forms its encoded address, and loads one aligned little-endian 1-byte value.

surface

scalar

{
  "classification": [
    "agu"
  ],
  "documentation": "docs/scalar/agu/LBU.PCR.md",
  "id": "PTO-SCALAR-LBU-PCR",
  "instruction_contract": {
    "artifact": "spec/evidence/instruction-contract-closure.json",
    "mnemonic": "LBU.PCR",
    "ndf_clause": "PTO-INST-SCALAR-LBU-PCR"
  },
  "mnemonic": "LBU.PCR",
  "readiness_subjects": [
    "ADR-0024",
    "ADR-0029",
    "ADR-0059"
  ],
  "semantic_tests": [
    "PTO-AVS-AGU-LBU-PCR-ALIAS-001",
    "PTO-AVS-AGU-LBU-PCR-BOUND-001",
    "PTO-AVS-AGU-LBU-PCR-EXEC-001",
    "PTO-AVS-AGU-LBU-PCR-FAULT-001"
  ],
  "source": "asl/scalar/agu/LBU.PCR.asl",
  "surface": "scalar",
  "tests": [
    "PTO-AVS-AGU-LBU-PCR-ALIAS-001",
    "PTO-AVS-AGU-LBU-PCR-BOUND-001",
    "PTO-AVS-AGU-LBU-PCR-EXEC-001",
    "PTO-AVS-AGU-LBU-PCR-FAULT-001",
    "PTO-AVS-SCALAR-LBU-PCR-DECODE-001"
  ]
}