SUBIW

assembly

[
  "subiw SrcL, uimm, ->{t, u, Rd}"
]

block

[]

catalog_indices

[
  438
]

catalog_records

[
  {
    "asm": "subiw SrcL, uimm, ->{t, u, Rd}",
    "constraints": [],
    "encoding": [
      {
        "index": 0,
        "mask": "0x0000707f",
        "match": "0x00001035",
        "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": "uimm12",
        "pieces": [
          {
            "instruction_lsb": 20,
            "value_lsb": 0,
            "width": 12
          }
        ],
        "signedness": "unsigned",
        "width": 12
      }
    ],
    "form_id": "subiw_32_51019ff77d0a",
    "length_bits": 32,
    "mnemonic": "SUBIW",
    "semantic_family": "ALU",
    "semantic_group": "ALU",
    "semantic_handler": "ScalarBinaryW",
    "semantic_summary": "SUBIW subtracts the zero-extended unsigned 12-bit immediate from SrcL[31:0] modulo 2^32, sign-extends the word result to XLEN, and publishes it through RegDst.",
    "status": "accepted"
  }
]

classification

[
  "alu"
]

contract

{
  "block_composition": [
    "none"
  ],
  "canonical_assembly": [
    "subiw SrcL, uimm, ->{t, u, Rd}"
  ],
  "defaults": [
    "SrcL, uimm12, and RegDst are required encoded fields; no field can be omitted.",
    "uimm12 is an unsigned 12-bit immediate from 0 through 4095. Encoded zero supplies numeric zero."
  ],
  "encoding_class": "standalone-encoded",
  "examples": [
    "subiw a0, 1, ->a0",
    "subiw u#1, 4095, ->t",
    "subiw zero, 0, ->zero"
  ],
  "exceptions": [
    "SUBIW raises no arithmetic exception: word subtraction wraps modulo 2^32 and is sign-extended to XLEN.",
    "A fixed-bit mismatch or unavailable selected T/U source raises Fault_IllegalInstruction before the destination effect and before TPC advances."
  ],
  "field_contracts": {},
  "field_zero_meanings": {
    "RegDst": "Encoded zero discards the result and does not modify any GPR or queue.",
    "SrcL": "Encoded zero reads the architectural zero GPR.",
    "uimm12": "Encoded zero supplies numeric zero."
  },
  "legality": [
    "All 32 SrcL 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: codes 0 and 24..29 discard, code 30 pushes U, code 31 pushes T, and codes 1..23 write absolute GPRs.",
    "Every unsigned 12-bit immediate from 0 through 4095 is legal; source bits above bit 31 do not affect the result."
  ],
  "memory_effects": [
    "none"
  ],
  "operands": [
    {
      "field": "RegDst",
      "role": "Reg5 scalar destination or discard selector"
    },
    {
      "field": "SrcL",
      "role": "Reg5 scalar source; only bits 31:0 participate"
    },
    {
      "field": "uimm12",
      "role": "unsigned 12-bit immediate"
    }
  ],
  "ordering": [
    "Snapshot SrcL before the destination effect. Repeated source and destination selectors therefore read the pre-instruction value.",
    "Successful execution publishes the sign-extended word result and then advances TPC by four bytes."
  ],
  "standalone_opcode": true,
  "state_effects": [
    "Subtract zero-extended uimm12 from SrcL[31:0] modulo 2^32, then sign-extend the 32-bit result to XLEN and publish it through RegDst.",
    "Codes 1..23 write a GPR; codes 0 and 24..29 discard; code 30 pushes U; code 31 pushes T. Source queue selections are non-consuming.",
    "No memory, reservation, descriptor, block, privilege, or control-flow state changes other than TPC advancing by four bytes after success."
  ]
}

depends_on

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

id

PTO-SCALAR-SUBIW

mnemonic

SUBIW

summary

SUBIW performs unsigned-immediate word subtraction and sign-extends the result to XLEN.

surface

scalar

{
  "classification": [
    "alu"
  ],
  "documentation": "docs/scalar/alu/SUBIW.md",
  "id": "PTO-SCALAR-SUBIW",
  "instruction_contract": {
    "artifact": "spec/evidence/instruction-contract-closure.json",
    "mnemonic": "SUBIW",
    "ndf_clause": "PTO-INST-SCALAR-SUBIW"
  },
  "mnemonic": "SUBIW",
  "readiness_subjects": [
    "ADR-0026",
    "ADR-0059",
    "ADR-0084"
  ],
  "semantic_tests": [
    "PTO-AVS-SCALAR-SUBIW-ALIASES-001",
    "PTO-AVS-SCALAR-SUBIW-RESULT-001"
  ],
  "source": "asl/scalar/alu/SUBIW.asl",
  "surface": "scalar",
  "tests": [
    "PTO-AVS-SCALAR-SUBIW-ALIASES-001",
    "PTO-AVS-SCALAR-SUBIW-DECODE-001",
    "PTO-AVS-SCALAR-SUBIW-RESULT-001"
  ]
}