# VSCALEFPD — Scale Packed Float64 Values With Float64 Values

Opcode/Instruction Op/En 64/32 bit Mode Support CPUID Feature Flag Description
EVEX.NDS.128.66.0F38.W1 2C /r VSCALEFPD xmm1 {k1}{z}, xmm2, xmm3/m128/m64bcst A V/V AVX512VL AVX512F Scale the packed double-precision floating-point values in xmm2 using values from xmm3/m128/m64bcst. Under writemask k1.
EVEX.NDS.256.66.0F38.W1 2C /r VSCALEFPD ymm1 {k1}{z}, ymm2, ymm3/m256/m64bcst A V/V AVX512VL AVX512F Scale the packed double-precision floating-point values in ymm2 using values from ymm3/m256/m64bcst. Under writemask k1.
EVEX.NDS.512.66.0F38.W1 2C /r VSCALEFPD zmm1 {k1}{z}, zmm2, zmm3/m512/m64bcst{er} A V/V AVX512F Scale the packed double-precision floating-point values in zmm2 using values from zmm3/m512/m64bcst. Under writemask k1.

## Instruction Operand Encoding ¶

 Op/En Tuple Type Operand 1 Operand 2 Operand 3 Operand 4 A Full ModRM:reg (w) EVEX.vvvv (r) ModRM:r/m (r) NA

### Description ¶

Performs a floating-point scale of the packed double-precision floating-point values in the first source operand by multiplying it by 2 power of the double-precision floating-point values in second source operand.

The equation of this operation is given by:

zmm1 := zmm2*2floor(zmm3).

Floor(zmm3) means maximum integer value ≤ zmm3.

If the result cannot be represented in double precision, then the proper overflow response (for positive scaling operand), or the proper underflow response (for negative scaling operand) is issued. The overflow and underflow responses are dependent on the rounding mode (for IEEE-compliant rounding), as well as on other settings in MXCSR (exception mask bits, FTZ bit), and on the SAE bit.

The first source operand is a ZMM/YMM/XMM register. The second source operand is a ZMM/YMM/XMM register, a 512/256/128-bit memory location or a 512/256/128-bit vector broadcasted from a 64-bit memory location. The destination operand is a ZMM/YMM/XMM register conditionally updated with writemask k1.

Handling of special-case input values are listed in Table 5-30 and Table 5-31.

### Operation ¶

SCALE(SRC1, SRC2)
{
TMP_SRC2 ← SRC2
TMP_SRC1 ← SRC1
IF (SRC2 is denormal AND MXCSR.DAZ) THEN TMP_SRC2=0
IF (SRC1 is denormal AND MXCSR.DAZ) THEN TMP_SRC1=0
/* SRC2 is a 64 bits floating-point value */
DEST[63:0]←TMP_SRC1[63:0] * POW(2, Floor(TMP_SRC2[63:0]))
}

#### VSCALEFPD (EVEX encoded versions) ¶

(KL, VL) = (2, 128), (4, 256), (8, 512)
IF (VL = 512) AND (EVEX.b = 1) AND (SRC2 *is register*)
THEN
SET_RM(EVEX.RC);
ELSE
SET_RM(MXCSR.RM);
FI;
FOR j←0 TO KL-1
i←j * 64
IF k1[j] OR *no writemask* THEN
IF (EVEX.b = 1) AND (SRC2 *is memory*)
THEN DEST[i+63:i]←SCALE(SRC1[i+63:i], SRC2[63:0]);
ELSE DEST[i+63:i]←SCALE(SRC1[i+63:i], SRC2[i+63:i]);
FI;
ELSE
THEN *DEST[i+63:i] remains unchanged*
ELSE
DEST[i+63:i] ← 0
FI
FI;
ENDFOR
DEST[MAXVL-1:VL] ← 0

### Intel C/C++ Compiler Intrinsic Equivalent ¶

VSCALEFPD __m512d _mm512_scalef_round_pd(__m512d a, __m512d b, int rounding);
VSCALEFPD __m512d _mm512_mask_scalef_round_pd(__m512d s, __mmask8 k, __m512d a, __m512d b, int rounding);
VSCALEFPD __m512d _mm512_scalef_pd(__m512d a, __m512d b);
VSCALEFPD __m256d _mm256_scalef_pd(__m256d a, __m256d b);