VEXP2PD — Approximation to the Exponential 2^x of Packed Double Precision Floating-PointValues With Less Than 2^-23 Relative Error

Opcode/Instruction Op/En 64/32 bit Mode Support CPUID Feature Flag Description
EVEX.512.66.0F38.W1 C8 /r VEXP2PD zmm1 {k1}{z}, zmm2/m512/m64bcst {sae} A V/V AVX512ER Computes approximations to the exponential 2^x (with less than 2^-23 of maximum relative error) of the packed double precision floating-point values from zmm2/m512/m64bcst and stores the floating-point result in zmm1with writemask k1.

Instruction Operand Encoding

Op/En Tuple Type Operand 1 Operand 2 Operand 3 Operand 4
A Full ModRM:reg (r, w) ModRM:r/m (r) N/A N/A


Computes the approximate base-2 exponential evaluation of the double precision floating-point values in the source operand (the second operand) and stores the results to 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.FTZ.

The source operand is a ZMM register, a 512-bit memory location or a 512-bit vector broadcasted from a 64-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




(KL, VL) = (8, 512)
FOR j := 0 TO KL-1
    i := j * 64
    IF k1[j] OR *no writemask* THEN
            IF (EVEX.b = 1) AND (SRC *is memory*)
                THEN DEST[i+63:i] := EXP2_23_DP(SRC[63:0])
                ELSE DEST[i+63:i] := EXP2_23_DP(SRC[i+63:i])
        IF *merging-masking* ; merging-masking
            THEN *DEST[i+63:i] remains unchanged*
            ELSE ; zeroing-masking
                DEST[i+63:i] := 0
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
Table 6-44. Special Values Behavior

Intel C/C++ Compiler Intrinsic Equivalent

VEXP2PD __m512d _mm512_exp2a23_round_pd (__m512d a, int sae);
VEXP2PD __m512d _mm512_mask_exp2a23_round_pd (__m512d a, __mmask8 m, __m512d b, int sae);
VEXP2PD __m512d _mm512_maskz_exp2a23_round_pd ( __mmask8 m, __m512d b, int sae);

SIMD Floating-Point Exceptions

Invalid (if SNaN input), Overflow.

Other Exceptions

See Table 2-46, “Type E2 Class Exception Conditions.”