PTO-ARCH-DATA-TYPES-FORMAT-E4M3This Operation comes directly from the instruction owner; the page does not rewrite its behavior.
// PTO-REQ-HARDWARE-NUMERIC-001: exact E4M3 encoding and finite values.
pure func E4M3NumericFormatDescriptor() => NumericFormatDescriptorbegin return NumericFormatDescriptor { available = TRUE, kind = NumericFormatKind_FixedBinary, carrier_bits = 8, lane_bits = 8, lanes_per_carrier = 1, sign_bits = 1, sign_bit = 7, exponent_bits_min = 4, exponent_bits_max = 4, fraction_bits_min = 3, fraction_bits_max = 3, exponent_bias_available = TRUE, exponent_bias = 7, required_low_zero_bits = 0, required_high_zero_bits = 0, has_zero = TRUE, has_signed_zero = TRUE, has_subnormal = TRUE, has_infinity = FALSE, has_quiet_nan = TRUE, has_signaling_nan = FALSE };end;
pure func E4M3FiniteDecomposition(value: bits(8)) => (boolean, boolean, Word, integer {-1074..1023})begin let exponent = value[6:3]; let fraction = value[2:0]; if exponent == Ones{4} && fraction == Ones{3} then return (FALSE, FALSE, Zeros{PTO_XLEN}, 0); elsif exponent == Zeros{4} then if fraction == Zeros{3} then return (TRUE, value[7] == '1', Zeros{PTO_XLEN}, 0); else return (TRUE, value[7] == '1', ZeroExtend{PTO_XLEN}(fraction), -9); end; else return (TRUE, value[7] == '1', LSL(Zeros{PTO_XLEN} + 1, 3) + ZeroExtend{PTO_XLEN}(fraction), (UInt(exponent) - (7 + 3)) as integer {-1074..1023}); end;end;pure func ClassifyE4M3(value: bits(8)) => NumericValueClassbegin let exponent = value[6:3]; let fraction = value[2:0]; if exponent == Ones{4} && fraction == Ones{3} then return NumericValue_QuietNaN; end; return NumericValueClassFromFiniteSign(value[7], exponent == Zeros{4} && fraction == Zeros{3}, exponent == Zeros{4} && fraction != Zeros{3});end;
pure func E4M3CanonicalNaN() => Wordbegin return Zeros{PTO_XLEN} + 0x7f;end;
pure func E4M3SignedZeroEncodings() => (Word, Word)begin return (Zeros{PTO_XLEN}, Zeros{PTO_XLEN} + 0x80);end;// PTO-UNIT: {"id":"PTO-ARCH-DATA-TYPES-FORMAT-E4M3","surface":"arch","classification":["data-types","formats","e4m3"],"depends_on":["PTO-ARCH-DATA-TYPES-FORMAT-DESCRIPTOR"]}// DOC-BEGIN: operation// PTO-REQ-HARDWARE-NUMERIC-001: exact E4M3 encoding and finite values.
pure func E4M3NumericFormatDescriptor() => NumericFormatDescriptorbegin return NumericFormatDescriptor { available = TRUE, kind = NumericFormatKind_FixedBinary, carrier_bits = 8, lane_bits = 8, lanes_per_carrier = 1, sign_bits = 1, sign_bit = 7, exponent_bits_min = 4, exponent_bits_max = 4, fraction_bits_min = 3, fraction_bits_max = 3, exponent_bias_available = TRUE, exponent_bias = 7, required_low_zero_bits = 0, required_high_zero_bits = 0, has_zero = TRUE, has_signed_zero = TRUE, has_subnormal = TRUE, has_infinity = FALSE, has_quiet_nan = TRUE, has_signaling_nan = FALSE };end;
pure func E4M3FiniteDecomposition(value: bits(8)) => (boolean, boolean, Word, integer {-1074..1023})begin let exponent = value[6:3]; let fraction = value[2:0]; if exponent == Ones{4} && fraction == Ones{3} then return (FALSE, FALSE, Zeros{PTO_XLEN}, 0); elsif exponent == Zeros{4} then if fraction == Zeros{3} then return (TRUE, value[7] == '1', Zeros{PTO_XLEN}, 0); else return (TRUE, value[7] == '1', ZeroExtend{PTO_XLEN}(fraction), -9); end; else return (TRUE, value[7] == '1', LSL(Zeros{PTO_XLEN} + 1, 3) + ZeroExtend{PTO_XLEN}(fraction), (UInt(exponent) - (7 + 3)) as integer {-1074..1023}); end;end;pure func ClassifyE4M3(value: bits(8)) => NumericValueClassbegin let exponent = value[6:3]; let fraction = value[2:0]; if exponent == Ones{4} && fraction == Ones{3} then return NumericValue_QuietNaN; end; return NumericValueClassFromFiniteSign(value[7], exponent == Zeros{4} && fraction == Zeros{3}, exponent == Zeros{4} && fraction != Zeros{3});end;
pure func E4M3CanonicalNaN() => Wordbegin return Zeros{PTO_XLEN} + 0x7f;end;
pure func E4M3SignedZeroEncodings() => (Word, Word)begin return (Zeros{PTO_XLEN}, Zeros{PTO_XLEN} + 0x80);end;// DOC-END: operation
E4M3 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 E4M3NumericFormatDescriptor, E4M3FiniteDecomposition, and ClassifyE4M3 in the ASL owner.
The descriptor uses a 8-bit carrier, a 8-bit logical lane, and 1 lane(s) per carrier. The lane has one sign bit at position 7, 4 exponent bit(s), 3 fraction bit(s), and exponent bias 7.
No carrier bits are constrained outside the sign, exponent, and fraction fields.
E4M3FiniteDecomposition reports whether a finite decomposition is available and, when available, returns the sign, an integer significand, and a binary exponent. ClassifyE4M3 separately assigns the raw lane to zero, subnormal, normal, infinity, or NaN classes supported by this format.
It has signed zero, subnormals, and a quiet-NaN class, but no infinity or signaling-NaN class. Only an all-one exponent together with an all-one fraction is non-finite.
0x00 and 0x80 are positive and negative zero; 0x7f is the canonical quiet NaN.
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 -9, while 0x7f is a quiet NaN and has no finite decomposition.
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-E4M3-STATIC-001tests/asl/arch/data-types/formats/e4m3/arch-static-e4m3-contract-001.aslebb232f912ad649cece4a3f1736da5134d0d85a7ecc55ac9b2cb6a860aab62faPTO-AVS-ARCH-E4M3-DECOMP-001tests/asl/arch/data-types/formats/e4m3/arch-bound-e4m3-decomp-001.aslfefdb43f96bc09e0d33caeb9f35974ceafbfe71e8a3cf973c11991e0675e9a12PTO-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",
"e4m3"
],
"documentation": "docs/arch/data-types/formats/e4m3.md",
"id": "PTO-ARCH-DATA-TYPES-FORMAT-E4M3",
"mnemonic": null,
"readiness_subjects": [
"ADR-0048"
],
"semantic_tests": [
"PTO-AVS-ARCH-E4M3-DECOMP-001"
],
"source": "asl/arch/data-types/formats/e4m3.asl",
"surface": "arch",
"tests": [
"PTO-AVS-ARCH-DATA-TYPES-FORMAT-E4M3-STATIC-001",
"PTO-AVS-ARCH-E4M3-DECOMP-001"
]
}0.58.5 · Release candidate7dc8b7e5b121d2b2499a2273bebff29e2cd86812ecbcef1094effdcdb279975c91cbe338371bea28a749d294fc118401d2aec836ad17df55adb842dc8d4347cba3334d64be84b7482db4ffeae43842aeae03ec5basl/arch/data-types/formats/e4m3.asl