VSCALEFSS — Scale Scalar Float32 Value With Float32 Value

Opcode/Instruction	Op/En	64/32 bit Mode Support	CPUID Feature Flag	Description
EVEX.LLIG.66.0F38.W0 2D /r VSCALEFSS xmm1 {k1}{z}, xmm2, xmm3/m32{er}	A	V/V	AVX512F	Scale the scalar single-precision floating-point value in xmm2 using floating-point value from xmm3/m32. Under writemask k1.

Instruction Operand Encoding ¶

Op/En	Tuple Type	Operand 1	Operand 2	Operand 3	Operand 4
A	Tuple1 Scalar	ModRM:reg (w)	EVEX.vvvv (r)	ModRM:r/m (r)	N/A

Description ¶

Performs a floating-point scale of the scalar single-precision floating-point value in the first source operand by multiplying it by 2 to the power of the float32 value in second source operand.

The equation of this operation is given by:

xmm1 := xmm2*2^floor(xmm3).

Floor(xmm3) means maximum integer value ≤ xmm3.

If the result cannot be represented in single-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.

EVEX encoded version: The first source operand is an XMM register. The second source operand is an XMM register or a memory location. The destination operand is an XMM register conditionally updated with writemask k1.

Handling of special-case input values are listed in Table 5-39 and Table 5-43.

Operation ¶

SCALE(SRC1, SRC2)
{
    ; Check for denormal operands
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 32 bits floating-point value */
DEST[31:0] := TMP_SRC1[31:0] * POW(2, Floor(TMP_SRC2[31:0]))
}

VSCALEFSS (EVEX encoded version) ¶

IF (EVEX.b= 1) and SRC2 *is a register*
    THEN
        SET_ROUNDING_MODE_FOR_THIS_INSTRUCTION(EVEX.RC);
    ELSE
        SET_ROUNDING_MODE_FOR_THIS_INSTRUCTION(MXCSR.RC);
FI;
IF k1[0] OR *no writemask*
    THEN DEST[31:0] := SCALE(SRC1[31:0], SRC2[31:0])
    ELSE
        IF *merging-masking* ; merging-masking
            THEN *DEST[31:0] remains unchanged*
            ELSE ; zeroing-masking
                DEST[31:0] := 0
        FI
FI;
DEST[127:32] := SRC1[127:32]
DEST[MAXVL-1:128] := 0

Intel C/C++ Compiler Intrinsic Equivalent ¶

VSCALEFSS __m128 _mm_scalef_round_ss(__m128 a, __m128 b, int);

VSCALEFSS __m128 _mm_mask_scalef_round_ss(__m128 s, __mmask8 k, __m128 a, __m128 b, int);

VSCALEFSS __m128 _mm_maskz_scalef_round_ss(__mmask8 k, __m128 a, __m128 b, int);

SIMD Floating-Point Exceptions ¶

Overflow, Underflow, Invalid, Precision, Denormal (for Src1).

Denormal is not reported for Src2.

Other Exceptions ¶

See Table 2-47, “Type E3 Class Exception Conditions.”