PTO-ARCH-DATA-TYPES-FORMAT-E3M2This Operation comes directly from the instruction owner; the page does not rewrite its behavior.
// PTO-REQ-HARDWARE-NUMERIC-001: exact zero-extended E3M2 values.
pure func E3M2NumericFormatDescriptor() => NumericFormatDescriptorbegin return NumericFormatDescriptor { available = TRUE, kind = NumericFormatKind_FixedBinary, carrier_bits = 8, lane_bits = 6, lanes_per_carrier = 1, sign_bits = 1, sign_bit = 5, exponent_bits_min = 3, exponent_bits_max = 3, fraction_bits_min = 2, fraction_bits_max = 2, exponent_bias_available = TRUE, exponent_bias = 3, required_low_zero_bits = 0, required_high_zero_bits = 2, has_zero = TRUE, has_signed_zero = TRUE, has_subnormal = TRUE, has_infinity = FALSE, has_quiet_nan = FALSE, has_signaling_nan = FALSE };end;
pure func E3M2FiniteDecomposition(value: bits(8)) => (boolean, boolean, Word, integer {-1074..1023})begin if value[7:6] != Zeros{2} then return (FALSE, FALSE, Zeros{PTO_XLEN}, 0); end; let exponent = value[4:2]; let fraction = value[1:0]; if exponent == Zeros{3} then if fraction == Zeros{2} then return (TRUE, value[5] == '1', Zeros{PTO_XLEN}, 0); else return (TRUE, value[5] == '1', ZeroExtend{PTO_XLEN}(fraction), -4); end; else return (TRUE, value[5] == '1', LSL(Zeros{PTO_XLEN} + 1, 2) + ZeroExtend{PTO_XLEN}(fraction), (UInt(exponent) - (3 + 2)) as integer {-1074..1023}); end;end;
pure func E3M2EncodingValid(value: bits(8)) => booleanbegin return value[7:6] == Zeros{2};end;pure func ClassifyE3M2(value: bits(8)) => NumericValueClassbegin let exponent = value[4:2]; let fraction = value[1:0]; return NumericValueClassFromFiniteSign(value[5], exponent == Zeros{3} && fraction == Zeros{2}, exponent == Zeros{3} && fraction != Zeros{2});end;
pure func E3M2SignedZeroEncodings() => (Word, Word)begin return (Zeros{PTO_XLEN}, Zeros{PTO_XLEN} + 0x20);end;// PTO-UNIT: {"id":"PTO-ARCH-DATA-TYPES-FORMAT-E3M2","surface":"arch","classification":["data-types","formats","e3m2"],"depends_on":["PTO-ARCH-DATA-TYPES-FORMAT-DESCRIPTOR"]}// DOC-BEGIN: operation// PTO-REQ-HARDWARE-NUMERIC-001: exact zero-extended E3M2 values.
pure func E3M2NumericFormatDescriptor() => NumericFormatDescriptorbegin return NumericFormatDescriptor { available = TRUE, kind = NumericFormatKind_FixedBinary, carrier_bits = 8, lane_bits = 6, lanes_per_carrier = 1, sign_bits = 1, sign_bit = 5, exponent_bits_min = 3, exponent_bits_max = 3, fraction_bits_min = 2, fraction_bits_max = 2, exponent_bias_available = TRUE, exponent_bias = 3, required_low_zero_bits = 0, required_high_zero_bits = 2, has_zero = TRUE, has_signed_zero = TRUE, has_subnormal = TRUE, has_infinity = FALSE, has_quiet_nan = FALSE, has_signaling_nan = FALSE };end;
pure func E3M2FiniteDecomposition(value: bits(8)) => (boolean, boolean, Word, integer {-1074..1023})begin if value[7:6] != Zeros{2} then return (FALSE, FALSE, Zeros{PTO_XLEN}, 0); end; let exponent = value[4:2]; let fraction = value[1:0]; if exponent == Zeros{3} then if fraction == Zeros{2} then return (TRUE, value[5] == '1', Zeros{PTO_XLEN}, 0); else return (TRUE, value[5] == '1', ZeroExtend{PTO_XLEN}(fraction), -4); end; else return (TRUE, value[5] == '1', LSL(Zeros{PTO_XLEN} + 1, 2) + ZeroExtend{PTO_XLEN}(fraction), (UInt(exponent) - (3 + 2)) as integer {-1074..1023}); end;end;
pure func E3M2EncodingValid(value: bits(8)) => booleanbegin return value[7:6] == Zeros{2};end;pure func ClassifyE3M2(value: bits(8)) => NumericValueClassbegin let exponent = value[4:2]; let fraction = value[1:0]; return NumericValueClassFromFiniteSign(value[5], exponent == Zeros{3} && fraction == Zeros{2}, exponent == Zeros{3} && fraction != Zeros{2});end;
pure func E3M2SignedZeroEncodings() => (Word, Word)begin return (Zeros{PTO_XLEN}, Zeros{PTO_XLEN} + 0x20);end;// DOC-END: operation
E3M2 is an assigned PTO numeric format. This page helps a reader connect its carrier layout, finite-value decomposition, and value classification; the exact contract remains in E3M2NumericFormatDescriptor, E3M2FiniteDecomposition, and ClassifyE3M2 in the ASL owner.
The descriptor uses a 8-bit carrier, a 6-bit logical lane, and 1 lane(s) per carrier. The lane has one sign bit at position 5, 3 exponent bit(s), 2 fraction bit(s), and exponent bias 3.
Bits 7:6 of the eight-bit carrier must be zero; the six-bit value occupies bits 5:0.
E3M2FiniteDecomposition reports whether a finite decomposition is available and, when available, returns the sign, an integer significand, and a binary exponent. ClassifyE3M2 separately assigns the raw lane to zero, subnormal, normal, infinity, or NaN classes supported by this format.
It has signed zero and subnormals, but no infinity or NaN class. A carrier with either constrained high bit set is rejected by the encoding-validity and finite-decomposition functions.
Encodings 0x00 and 0x20 are positive and negative zero.
The finite-decomposition function reports availability with its returned tuple; value classification is a separate function result.
This example illustrates how to read the functions; it does not add an encoding rule.
For example, 0x01 decomposes to positive significand 1 with exponent -4; 0x80 is not a valid E3M2 encoding because bit 7 is set.
Bodies come from owning ASL. Dragging or buttons change only this page-session view order.
No NDF clause is attached to this unit.
8 matching entries
PTO-AVS-ARCH-DATA-TYPES-FORMAT-E3M2-STATIC-001tests/asl/arch/data-types/formats/e3m2/arch-static-e3m2-contract-001.asle0335ef6c5baf96ec5fb0961ce961d7b553315fa36358067589aa711e86c1bdaPTO-AVS-ARCH-E3M2-DECOMP-001tests/asl/arch/data-types/formats/e3m2/arch-bound-e3m2-decomp-001.asle942008d7104703a8ee6e304e04dcca247d221b2a2a5f536a86cbcbb1bef2b93PTO-EVIDENCE-RELEASE-TRACEABILITYPTO-EVIDENCE-RELEASE-TRACEABILITYspec/evidence/release-traceability-readiness.jsonc7327021d39dc67ac5564bc55073b3870a397d79ac8d9648284d56e33bc14a3ePTO-EVIDENCE-INSTRUCTION-CONTRACT-CLOSUREPTO-EVIDENCE-INSTRUCTION-CONTRACT-CLOSUREspec/evidence/instruction-contract-closure.json3ef2bb62421c79dff8fa77a1c7983923b523244b8090812883ef81286ca8106aPTO-EVIDENCE-ARCHITECTURE-READINESSPTO-EVIDENCE-ARCHITECTURE-READINESSspec/evidence/architecture-readiness.json4b0b85199101251bea744e0f3591cc31906909dc80d5ab651c417a936036a004PTO-EVIDENCE-RELEASE-GATE-READINESSPTO-EVIDENCE-RELEASE-GATE-READINESSspec/evidence/release-gate-readiness.jsona0f4d2b6920c08981ea55fd8ef820708a40d4feb5402c5150e8e9ab532d84ce0PTO-EVIDENCE-RELEASE-MANIFESTPTO-EVIDENCE-RELEASE-MANIFESTspec/release-manifest.json1a64c109ed7a90351c41e2a418b3c0ebaf8ad975838986d2101385186b85c0d8Loading ADR-0048…
ADR-0048docs/status/decisions/0048-numeric-format-value-classification.mdce3ecd1851e22b5517d07076ab8bd2db36b6b4582111c761db19240275853d9c{
"classification": [
"data-types",
"formats",
"e3m2"
],
"documentation": "docs/arch/data-types/formats/e3m2.md",
"id": "PTO-ARCH-DATA-TYPES-FORMAT-E3M2",
"mnemonic": null,
"readiness_subjects": [
"ADR-0048"
],
"semantic_tests": [
"PTO-AVS-ARCH-E3M2-DECOMP-001"
],
"source": "asl/arch/data-types/formats/e3m2.asl",
"surface": "arch",
"tests": [
"PTO-AVS-ARCH-DATA-TYPES-FORMAT-E3M2-STATIC-001",
"PTO-AVS-ARCH-E3M2-DECOMP-001"
]
}0.58.5 · Release candidate7dc8b7e5b121d2b2499a2273bebff29e2cd868127bfe85b0c248ee27de72f0dd20adee81e6378a26231e456ec2bcc6e55536e39d038531b8ecb382ef2aad78b8802c46b7af9132ee8673d13c4078957a22a1b594asl/arch/data-types/formats/e3m2.asl