VEXP2PS — Approximation to the Exponential 2^x of Packed Single 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.W0 C8 /r VEXP2PS zmm1 {k1}{z}, zmm2/m512/m32bcst {sae}	A	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 Tuple Type Operand 1 Operand 2 Operand 3 Operand 4
A Full ModRM:reg (r, w) ModRM:r/m (r) N/A N/A

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 write-mask 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 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 := 0 TO KL-1
    i := j * 32
    IF k1[j] OR *no writemask* THEN
            IF (EVEX.b = 1) AND (SRC *is memory*)
                THEN DEST[i+31:i] := EXP2_23_SP(SRC[31:0])
                ELSE DEST[i+31:i] := 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] := 0
        FI;
    FI;
ENDFOR;

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 6-45. Special Values Behavior

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