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FLOGNP1A

Operation

Approximates natural log of one plus the source, with minus one as the divide-by-zero boundary.

Assembler Syntax

FLOGNP1A.{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 \(\ln(1 + x)\) reference without an intermediate rounded addition under the selected FPTRANSA accuracy contract. The reference domain includes finite \(x \ge -1\) and positive infinity; \(-1\) is the DZ boundary.

The required FPTRANSA_ACCURACY contract is 0x0042.

Special values

  • Source equal to -1: DZ is generated and the result is -infinity.

  • Source below -1: NV is generated and the result is the architectural default quiet NaN.

  • Positive infinity: the result is +infinity.

  • Zero source: the result is the source.

Exact anchors

  • \(\operatorname{log1p}(+0) = +0\)

  • \(\operatorname{log1p}(-0) = -0\)

  • \(\operatorname{log1p}(-1) = -\infty\)

Required properties

  • strictly increasing on \((-1, +\infty)\)

2.75in

Encodings

FLOGNP1A.{S|D}(z) Fn(s), Fn(d)

Format: Instruction format for FLOGNP1A.{S|D}(z) Fn(s), Fn(d)

Format: Instruction format for FLOGNP1A.{S|D}(z) Fn(s), Fn(d)