VGETEXPPD - Convert Exponents of Packed Double Precision Floating-Point Values to Double Precision Floating-Point Values

Opcode/ Instruction

Op/ En

64/32 bit Mode Support

CPUID Feature Flag

Description

EVEX.128.66.0F38.W1 42 /r VGETEXPPD xmm1 {k1}{z}, xmm2/m128/m64bcst

A

V/V

AVX512VL AVX512F

Convert the exponent of packed double precision floating-point values in the source operand to double precision floating-point results representing unbiased integer exponents and stores the results in the destination register.

EVEX.256.66.0F38.W1 42 /r VGETEXPPD ymm1 {k1}{z}, ymm2/m256/m64bcst

A

V/V

AVX512VL AVX512F

Convert the exponent of packed double precision floating-point values in the source operand to double precision floating-point results representing unbiased integer exponents and stores the results in the destination register.

EVEX.512.66.0F38.W1 42 /r VGETEXPPD zmm1 {k1}{z}, zmm2/m512/m64bcst{sae}

A

V/V

AVX512F

Convert the exponent of packed double precision floating-point values in the source operand to double precision floating-point results representing unbiased integer exponents and stores the results in the destination under writemask k1.

Instruction Operand Encoding

Op/En

Tuple Type

Operand 1

Operand 2

Operand 3

Operand 4

A

Full

ModRM:reg (w)

ModRM:r/m (r)

N/A

N/A

Description

Extracts the biased exponents from the normalized double precision floating-point representation of each qword data element of the source operand (the second operand) as unbiased signed integer value, or convert the denormal representation of input data to unbiased negative integer values. Each integer value of the unbiased exponent is converted to double precision floating-point value and written to the corresponding qword elements of the destination operand (the first operand) as double precision floating-point numbers.

The destination operand is a ZMM/YMM/XMM register and updated under the writemask. The source operand can be 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.

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

Each GETEXP operation converts the exponent value into a floating-point number (permitting input value in denormal representation). Special cases of input values are listed in Table 5-5.

The formula is:

GETEXP(x) = floor(log2(|x|)) Notation floor(x) stands for the greatest integer not exceeding real number x.

Table 5-5. VGETEXPPD/SD Special Cases

Input Operand

Result

Comments

src1 = NaN

QNaN(src1)

0 < |src1| < INF

floor(log2(|src1|))

If (SRC = SNaN) then #IE If (SRC = denormal) then #DE

| src1| = +INF

+INF

| src1| = 0

-INF

Operation 

NormalizeExpTinyDPFP(SRC[63:0])
{
   // Jbit is the hidden integral bit of a floating-point number. In case of denormal number it has the value of ZERO.
   Src.Jbit := 0;
   Dst.exp := 1; 
   Dst.fraction := SRC[51:0];
   WHILE(Src.Jbit = 0)
   {
       Src.Jbit := Dst.fraction[51];            // Get the fraction MSB
       Dst.fraction := Dst.fraction << 1 ;          // One bit shift left
       Dst.exp-- ;             // Decrement the exponent
   }
   Dst.fraction := 0;            // zero out fraction bits
   Dst.sign := 1;               // Return negative sign
   TMP[63:0] := MXCSR.DAZ? 0 : (Dst.sign << 63) OR (Dst.exp << 52) OR (Dst.fraction) ;
   Return (TMP[63:0]);
}
ConvertExpDPFP(SRC[63:0])
{
   Src.sign := 0;                // Zero out sign bit
   Src.exp := SRC[62:52];
   Src.fraction := SRC[51:0];
   // Check for NaN
   IF (SRC = NaN) 
   {
       IF ( SRC = SNAN ) SET IE;
       Return QNAN(SRC);
   }
   // Check for +INF
   IF (Src = +INF) RETURN (Src);
   // check if zero operand
   IF ((Src.exp = 0) AND ((Src.fraction = 0) OR (MXCSR.DAZ = 1))) Return (-INF);
   }
   ELSE          // check if denormal operand (notice that MXCSR.DAZ = 0)
   {
       IF ((Src.exp = 0) AND (Src.fraction != 0)) 
       {
            TMP[63:0] := NormalizeExpTinyDPFP(SRC[63:0]) ;      // Get Normalized Exponent
            Set #DE
       }
       ELSE         // exponent value is correct
       {
            TMP[63:0] := (Src.sign << 63) OR (Src.exp << 52) OR (Src.fraction) ;
       }
       TMP := SAR(TMP, 52) ;           // Shift Arithmetic Right
       TMP := TMP - 1023;             // Subtract Bias
       Return CvtI2D(TMP);            // Convert INT to double precision floating-point number
   }
}

VGETEXPPD (EVEX encoded versions) 

(KL, VL) = (2, 128), (4, 256), (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] :=
            ConvertExpDPFP(SRC[63:0])
                ELSE 
                     DEST[i+63:i] :=
            ConvertExpDPFP(SRC[i+63:i])
            FI;
       ELSE 
            IF *merging-masking*                ; merging-masking
                THEN *DEST[i+63:i] remains unchanged*
                ELSE                            ; zeroing-masking
                     DEST[i+63:i] := 0
            FI
   FI;
ENDFOR
DEST[MAXVL-1:VL] := 0

Intel C/C++ Compiler Intrinsic Equivalent 

VGETEXPPD __m512d _mm512_getexp_pd(__m512d a);
VGETEXPPD __m512d _mm512_mask_getexp_pd(__m512d s, __mmask8 k, __m512d a);
VGETEXPPD __m512d _mm512_maskz_getexp_pd( __mmask8 k, __m512d a);
VGETEXPPD __m512d _mm512_getexp_round_pd(__m512d a, int sae);
VGETEXPPD __m512d _mm512_mask_getexp_round_pd(__m512d s, __mmask8 k, __m512d a, int sae);
VGETEXPPD __m512d _mm512_maskz_getexp_round_pd( __mmask8 k, __m512d a, int sae);
VGETEXPPD __m256d _mm256_getexp_pd(__m256d a);
VGETEXPPD __m256d _mm256_mask_getexp_pd(__m256d s, __mmask8 k, __m256d a);
VGETEXPPD __m256d _mm256_maskz_getexp_pd( __mmask8 k, __m256d a);
VGETEXPPD __m128d _mm_getexp_pd(__m128d a);
VGETEXPPD __m128d _mm_mask_getexp_pd(__m128d s, __mmask8 k, __m128d a);
VGETEXPPD __m128d _mm_maskz_getexp_pd( __mmask8 k, __m128d a);

SIMD Floating-Point Exceptions

Invalid, Denormal.

Other Exceptions

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

Additionally:

#UD

If EVEX.vvvv != 1111B.