VEXP2PS—Approximation to the Exponential 2^x of Packed Single-Precision Floating-Point Values with Less Than 2^-23 Relative Error

Opcode/Instruction Op /En 64/32 bit Mode Support CPUID Feature Flag Description

EVEX.512.66.0F38.W0 C8 /r

VEXP2PS zmm1 {k1}{z}, zmm2/m512/m32bcst {sae}

 FV V/V AVX512ER Computes approximations to the exponential 2^x (with less than 2^-23 of maximum relative error) of the packed single-precision floating-point values from zmm2/m512/m32bcst and stores the floating-point result in zmm1with writemask k1.

Instruction Operand Encoding

Op/En Operand 1 Operand 2 Operand 3 Operand 4
FV ModRM:reg (r, w) ModRM:r/m (r) NA NA

Description

Computes the approximate base-2 exponential evaluation of the single-precision floating-point values in the source operand (the second operand) and store the results in the destination operand (the first operand) using the writemask k1. The approximate base-2 exponential is evaluated with less than 2^-23 of relative error.

Denormal input values are treated as zeros and do not signal #DE, irrespective of MXCSR.DAZ. Denormal results are flushed to zeros and do not signal #UE, irrespective of MXCSR.FZ.

The source operand is a ZMM register, a 512-bit memory location, or a 512-bit vector broadcasted from a 32-bit memory location. The destination operand is a ZMM register, conditionally updated using writemask k1.

EVEX.vvvv is reserved and must be 1111b otherwise instructions will #UD.

A numerically exact implementation of VEXP2xx can be found at https://software.intel.com/en-us/articles/refer-ence-implementations-for-IA-approximation-instructions-vrcp14-vrsqrt14-vrcp28-vrsqrt28-vexp2.

Operation

VEXP2PS

(KL, VL) = (16, 512)

FOR j (cid:197) 0 TO KL-1

i (cid:197) j * 32

IF k1[j] OR *no writemask* THEN

IF (EVEX.b = 1) AND (SRC *is memory*)

THEN DEST[i+31:i] (cid:197) EXP2_23_SP(SRC[31:0])

ELSE DEST[i+31:i] (cid:197) EXP2_23_SP(SRC[i+31:i])

FI;

ELSE

IF *merging-masking*

; merging-masking

THEN *DEST[i+31:i] remains unchanged*

ELSE

; zeroing-masking

DEST[i+31:i] (cid:197) 0

FI;

FI;

ENDFOR;

Table 5-5. Special Values Behavior

Source Input Result Comments
NaN QNaN(src) If (SRC = SNaN) then #I
+∞ +∞
+/-0 1.0f Exact result
-∞ +0.0f
Integral value N 2^ (N) Exact result

Intel C/C++ Compiler Intrinsic Equivalent

VEXP2PS __m512 _mm512_exp2a23_round_ps (__m512 a, int sae);

VEXP2PS __m512 _mm512_mask_exp2a23_round_ps (__m512 a, __mmask16 m, __m512 b, int sae);

VEXP2PS __m512 _mm512_maskz_exp2a23_round_ps (__mmask16 m, __m512 b, int sae);

SIMD Floating-Point Exceptions

Invalid (if SNaN input), Overflow

Other Exceptions

See Exceptions Type E2.