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FLOGNA

Operation

Approximates natural logarithm for positive values, with zero as the divide-by-zero boundary.

Assembler Syntax

FLOGNA.{S|D}(z) Fn(s), Fn(d)

Privilege

Unprivileged

Required CPUID flags

FP

FPTRANSA

Repeat eligibility

REP eligible

After DAZ, computes an implementation-bounded S- or D-format approximation of the ln(x) reference under the selected FPTRANSA accuracy contract. The reference domain includes positive finite values and positive infinity; signed zero is the DZ boundary.

The required FPTRANSA_ACCURACY contract is 0x0041.

Special values

  • Zero source: DZ is generated and the result is -infinity.

  • Negative source: NV is generated and the result is the architectural default quiet NaN.

  • Positive infinity: the result is +infinity.

  • Unit source: the result is positive zero.

Exact anchors

  • ln(+1) = +0

  • ln(signed 0) = -infinity

  • ln(+infinity) = +infinity

Required properties

  • strictly increasing on the positive domain

2.75in

Encodings

FLOGNA.{S|D}(z) Fn(s), Fn(d)

Format: Instruction format for FLOGNA.{S|D}(z) Fn(s), Fn(d)

Format: Instruction format for FLOGNA.{S|D}(z) Fn(s), Fn(d)