FEXPA

Floating-point exponential accelerator

The FEXPA instruction accelerates the polynomial series calculation of the exp(x) function.

The double-precision variant copies the low 52 bits of an entry from a hard-wired table of 64-bit coefficients, indexed by the low 6 bits of each element of the source vector, and prepends to that the next 11 bits of the source element (src<16:6>), setting the sign bit to zero.

The single-precision variant copies the low 23 bits of an entry from hard-wired table of 32-bit coefficients, indexed by the low 6 bits of each element of the source vector, and prepends to that the next 8 bits of the source element (src<13:6>), setting the sign bit to zero.

The half-precision variant copies the low 10 bits of an entry from hard-wired table of 16-bit coefficients, indexed by the low 5 bits of each element of the source vector, and prepends to that the next 5 bits of the source element (src<9:5>), setting the sign bit to zero.

A coefficient table entry with index m holds the floating-point value 2(m/64), or for the half-precision variant 2(m/32). This instruction is unpredicated.

This instruction is illegal when executed in Streaming SVE mode, unless FEAT_SME_FA64 is implemented and enabled.

313029282726252423222120191817161514131211109876543210
00000100size100000101110ZnZd

FEXPA <Zd>.<T>, <Zn>.<T>

if !IsFeatureImplemented(FEAT_SVE) then UNDEFINED; if size == '00' then UNDEFINED; constant integer esize = 8 << UInt(size); constant integer n = UInt(Zn); constant integer d = UInt(Zd);

Assembler Symbols

<Zd>

Is the name of the destination scalable vector register, encoded in the "Zd" field.

<T>

Is the size specifier, encoded in size:

size <T>
00 RESERVED
01 H
10 S
11 D
<Zn>

Is the name of the source scalable vector register, encoded in the "Zn" field.

Operation

CheckNonStreamingSVEEnabled(); constant integer VL = CurrentVL; constant integer PL = VL DIV 8; constant integer elements = VL DIV esize; constant bits(VL) operand = Z[n, VL]; bits(VL) result; for e = 0 to elements-1 constant bits(esize) element = Elem[operand, e, esize]; Elem[result, e, esize] = FPExpA(element); Z[d, VL] = result;


Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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