LR.B

assembly

[
  "lr.b [SrcL], ->Rd",
  "lr.b.aq [SrcL], ->Rd",
  "lr.b.rl [SrcL], ->Rd",
  "lr.b.f [SrcL], ->Rd",
  "lr.b.aqrl [SrcL], ->Rd",
  "lr.b.aqf [SrcL], ->Rd",
  "lr.b.rlf [SrcL], ->Rd",
  "lr.b.aqrlf [SrcL], ->Rd"
]

block

[]

catalog_indices

[
  334
]

catalog_records

[
  {
    "asm": "lr.b<.{aq, rl, f, aqrl, aqf, rlf, aqrlf}> [SrcL], {->t, ->u, ->Rd}",
    "constraints": [],
    "encoding": [
      {
        "index": 0,
        "mask": "0xf000707f",
        "match": "0x0000000b",
        "width_bits": 32
      }
    ],
    "encoding_kind": "L32",
    "fields": [
      {
        "name": "RegDst",
        "pieces": [
          {
            "instruction_lsb": 7,
            "value_lsb": 0,
            "width": 5
          }
        ],
        "signedness": "encoding-defined",
        "width": 5
      },
      {
        "name": "SrcL",
        "pieces": [
          {
            "instruction_lsb": 15,
            "value_lsb": 0,
            "width": 5
          }
        ],
        "signedness": "encoding-defined",
        "width": 5
      },
      {
        "name": "SrcZero",
        "pieces": [
          {
            "instruction_lsb": 20,
            "value_lsb": 0,
            "width": 5
          }
        ],
        "signedness": "encoding-defined",
        "width": 5
      },
      {
        "name": "aq",
        "pieces": [
          {
            "instruction_lsb": 26,
            "value_lsb": 0,
            "width": 1
          }
        ],
        "signedness": "encoding-defined",
        "width": 1
      },
      {
        "name": "far",
        "pieces": [
          {
            "instruction_lsb": 27,
            "value_lsb": 0,
            "width": 1
          }
        ],
        "signedness": "encoding-defined",
        "width": 1
      },
      {
        "name": "rl",
        "pieces": [
          {
            "instruction_lsb": 25,
            "value_lsb": 0,
            "width": 1
          }
        ],
        "signedness": "encoding-defined",
        "width": 1
      }
    ],
    "form_id": "lr_b_32_cf80903a761a",
    "length_bits": 32,
    "mnemonic": "LR.B",
    "semantic_family": "AMO",
    "semantic_group": "AMO",
    "semantic_handler": "LoadReserved",
    "semantic_summary": "LR.B loads one byte, establishes a 64-byte-line reservation, and publishes the prior value.",
    "status": "accepted"
  }
]

classification

[
  "amo"
]

contract

{
  "block_composition": [
    "none"
  ],
  "canonical_assembly": [
    "lr.b [SrcL], ->Rd",
    "lr.b.aq [SrcL], ->Rd",
    "lr.b.rl [SrcL], ->Rd",
    "lr.b.f [SrcL], ->Rd",
    "lr.b.aqrl [SrcL], ->Rd",
    "lr.b.aqf [SrcL], ->Rd",
    "lr.b.rlf [SrcL], ->Rd",
    "lr.b.aqrlf [SrcL], ->Rd"
  ],
  "defaults": [
    "SrcL and RegDst are required Reg5 fields. Encoded source zero reads the architectural zero register; encoded destination zero discards the loaded value.",
    "SrcZero is an ignored alias field. Every encoding 0..31 selects the same operation and no register or queue is read through SrcZero.",
    "aq=0 and rl=0 select relaxed ordering. aq=1 selects acquire, rl=1 selects release, and aq=1 with rl=1 selects acquire-release.",
    "far=0 selects the default flat-address route. far=1 is a profile routing hint; the reference profile preserves the same architectural address and reservation behavior."
  ],
  "encoding_class": "standalone-encoded",
  "examples": [
    "lr.b [a0], ->a1",
    "lr.b.aqrl [t#1], ->u",
    "lr.b.f [sp], ->t"
  ],
  "exceptions": [
    "Every byte address is naturally aligned. Alignment, translation, and read permission are checked before effects and report the original address.",
    "On a fault, no destination or queue value is published, no memory event is emitted, the prior reservation is preserved, and TPC does not advance. Trap entry saves the original TPC and recovery restores it for full reissue.",
    "An undecodable fixed-bit pattern raises Fault_IllegalInstruction before effects. SrcZero, aq, rl, far, and all Reg5 values have no reserved encodings."
  ],
  "field_contracts": {},
  "field_zero_meanings": {
    "RegDst": "Encoded zero discards the loaded value.",
    "SrcL": "Encoded zero reads the architectural zero register as the load address.",
    "SrcZero": "Encoded zero is one of 32 ignored aliases and supplies no operand.",
    "aq": "Encoded zero disables acquire ordering.",
    "far": "Encoded zero selects the default flat-address route.",
    "rl": "Encoded zero disables release ordering."
  },
  "legality": [
    "All 32 SrcL Reg5 encodings are assigned: 0..23 select absolute GPRs, 24..27 select T#1..T#4, and 28..31 select U#1..U#4.",
    "All 32 RegDst encodings are assigned. Code 0 and codes 24..29 discard, code 30 pushes U, code 31 pushes T, and codes 1..23 write the named absolute GPR.",
    "All 32 SrcZero encodings are ignored aliases. All aq, rl, and far combinations are assigned.",
    "Every byte address is naturally aligned."
  ],
  "memory_effects": [
    "Read one 1-byte little-endian byte after complete access preflight and record one ordered load event at the translated address.",
    "After a successful load, replace any prior local reservation with the original address and width 1; SC matching uses the containing 64-byte reservation granule.",
    "The 8-bit old value is zero-extended to XLEN."
  ],
  "operands": [
    {
      "field": "SrcL",
      "role": "Reg5 load address source"
    },
    {
      "field": "SrcZero",
      "role": "ignored 5-bit alias field"
    },
    {
      "field": "RegDst",
      "role": "Reg5 loaded-value destination"
    },
    {
      "field": "aq",
      "role": "acquire ordering bit"
    },
    {
      "field": "rl",
      "role": "release ordering bit"
    },
    {
      "field": "far",
      "role": "flat-address routing hint"
    }
  ],
  "ordering": [
    "aq=0,rl=0 records relaxed ordering; aq=1,rl=0 acquire; aq=0,rl=1 release; aq=1,rl=1 acquire-release.",
    "far changes only the route hint in the reference profile and does not change the address, event order, loaded value, or reservation."
  ],
  "standalone_opcode": true,
  "state_effects": [
    "Snapshot SrcL before any memory, reservation, or destination effect. SrcZero is not read.",
    "On success, publish the byte old value only after the load completes and establish the 64-byte-line reservation.",
    "The 8-bit old value is zero-extended to XLEN.",
    "Successful execution advances TPC by four bytes. Fault entry saves the original TPC, redirects the live TPC, and recovery restores the saved TPC for full reissue."
  ]
}

depends_on

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

id

PTO-SCALAR-LR-B

mnemonic

LR.B

summary

LR.B loads one byte, establishes a 64-byte-line reservation, and publishes the prior value.

surface

scalar

{
  "classification": [
    "amo"
  ],
  "documentation": "docs/scalar/amo/LR.B.md",
  "id": "PTO-SCALAR-LR-B",
  "instruction_contract": {
    "artifact": "spec/evidence/instruction-contract-closure.json",
    "mnemonic": "LR.B",
    "ndf_clause": "PTO-INST-SCALAR-LR-B"
  },
  "mnemonic": "LR.B",
  "readiness_subjects": [
    "ADR-0020",
    "ADR-0030",
    "ADR-0059"
  ],
  "semantic_tests": [
    "PTO-AVS-SCALAR-LR-B-ALIASES-001",
    "PTO-AVS-SCALAR-LR-B-PRECISE-001",
    "PTO-AVS-SCALAR-LR-B-RESERVE-001"
  ],
  "source": "asl/scalar/amo/LR.B.asl",
  "surface": "scalar",
  "tests": [
    "PTO-AVS-SCALAR-LR-B-ALIASES-001",
    "PTO-AVS-SCALAR-LR-B-DECODE-001",
    "PTO-AVS-SCALAR-LR-B-PRECISE-001",
    "PTO-AVS-SCALAR-LR-B-RESERVE-001"
  ]
}