VGETMANTPS — Extract Float32 Vector of Normalized Mantissas from Float32 Vector

Instruction Operand Encoding ¶

Description ¶

Convert single-precision floating values in the source operand (the second operand) to SP FP values with the mantissa normalization and sign control specified by the imm8 byte, see Figure 5-15. The converted results are written to the destination operand (the first operand) using writemask k1. The normalized mantissa is specified by interv (imm8[1:0]) and the sign control (sc) is specified by bits 3:2 of the immediate byte.

The destination operand is a ZMM/YMM/XMM register 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 32-bit memory location.

For each input SP FP value x, The conversion operation is:

GetMant(x) = ±2^k|x.significand|

where:

1 <= |x.significand| < 2

Unbiased exponent k depends on the interval range defined by interv and whether the exponent of the source is even or odd. The sign of the final result is determined by sc and the source sign.

if interv != 0 then k = -1, otherwise K = 0. The encoded value of imm8[1:0] and sign control are shown

in Figure 5-15.

Each converted SP FP result is encoded according to the sign control, the unbiased exponent k (adding bias) and a mantissa normalized to the range specified by interv.

The GetMant() function follows Table 5-16 when dealing with floating-point special numbers.

This instruction is writemasked, so only those elements with the corresponding bit set in vector mask register k1 are computed and stored into the destination. Elements in zmm1 with the corresponding bit clear in k1 retain their previous values.

Note: EVEX.vvvv is reserved and must be 1111b, VEX.L must be 0; otherwise instructions will #UD.

Operation ¶

GetNormalizeMantissaSP(SRC[31:0] , SignCtrl[1:0], Interv[1:0])
{
    // Extracting the SRC sign, exponent and mantissa fields
    Dst.sign←SignCtrl[0] ? 0 : Src[31]; // Get sign bit
    Dst.exp←SRC[30:23]; ; Get original exponent value
    Dst.fraction←SRC[22:0];; Get original fraction value
    ZeroOperand←(Dst.exp = 0) AND (Dst.fraction = 0);
    DenormOperand←(Dst.exp = 0h) AND (Dst.fraction != 0);
    InfiniteOperand←(Dst.exp = 0FFh) AND (Dst.fraction = 0);
    NaNOperand←(Dst.exp = 0FFh) AND (Dst.fraction != 0);
    // Check for NAN operand
    IF (NaNOperand)
    { IF (SRC = SNaN) {Set #IE;}
        Return QNAN(SRC);
    }
    // Check for Zero and Infinite operands
    IF ((ZeroOperand) OR (InfiniteOperand)
    { Dst.exp←07Fh;
                        // Override exponent with BIAS
        Return ((Dst.sign<<31) | (Dst.exp<<23) | (Dst.fraction));
    }
    // Check for negative operand (including -0.0)
    IF ((Src[31] = 1) AND SignCtrl[1])
    { Set #IE;
        Return QNaN_Indefinite;
    }
    // Checking for denormal operands
    IF (DenormOperand)
    { IF (MXCSR.DAZ=1) Dst.fraction←0;// Zero out fraction
        ELSE
        {
            // Jbit is the hidden integral bit. Zero in case of denormal operand.
            Src.Jbit←0;
                    // Zero Src Jbit
            Dst.exp←07Fh;
                    // Override exponent with BIAS
            WHILE (Src.Jbit = 0) {
                    // normalize mantissa
                Src.Jbit←Dst.fraction[22]; // Get the fraction MSB
                Dst.fraction←(Dst.fraction << 1);
                                // Start normalizing the mantissa
                Dst.exp--; // Adjust the exponent
            }
            SET #DE; // Set DE bit
        }
    }
    // Checking for exponent response
    Unbiased.exp←Dst.exp – 07Fh;
                        // subtract the bias from exponent
    IsOddExp←Unbiased.exp[0];
                        // recognized unbiased ODD exponent
    SignalingBit ← Dst.fraction[22];
    CASE (interv[1:0])
        00: Dst.exp←07Fh;
                            // This is the bias
        01: Dst.exp←(IsOddExp) ? 07Eh : 07Fh;
                                // either bias-1, or bias
        10: Dst.exp←07Eh;
                            // bias-1
        11: Dst.exp←(SignalingBit) ? 07Eh : 07Fh;
                                // either bias-1, or bias
    ESAC
    // Form the final destination
    DEST[31:0]←(Dst.sign << 31) OR (Dst.exp << 23) OR (Dst.fraction);
    Return (DEST);
}

VGETMANTPS (EVEX encoded versions) ¶

(KL, VL) = (4, 128), (8, 256), (16, 512)
SignCtrl[1:0] ← IMM8[3:2];
Interv[1:0] ← IMM8[1:0];
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] ← GetNormalizedMantissaSP(SRC[31:0], SignCtrl, Interv)
                ELSE
                    DEST[i+31:i] ← GetNormalizedMantissaSP(SRC[i+31:i], SignCtrl, Interv)
            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
DEST[MAXVL-1:VL] ← 0

Intel C/C++ Compiler Intrinsic Equivalent ¶

VGETMANTPS __m512 _mm512_getmant_ps( __m512 a, enum intv, enum sgn);

VGETMANTPS __m512 _mm512_mask_getmant_ps(__m512 s, __mmask16 k, __m512 a, enum intv, enum sgn;

VGETMANTPS __m512 _mm512_maskz_getmant_ps(__mmask16 k, __m512 a, enum intv, enum sgn);

VGETMANTPS __m512 _mm512_getmant_round_ps( __m512 a, enum intv, enum sgn, int r);

VGETMANTPS __m512 _mm512_mask_getmant_round_ps(__m512 s, __mmask16 k, __m512 a, enum intv, enum sgn, int r);

VGETMANTPS __m512 _mm512_maskz_getmant_round_ps(__mmask16 k, __m512 a, enum intv, enum sgn, int r);

VGETMANTPS __m256 _mm256_getmant_ps( __m256 a, enum intv, enum sgn);

VGETMANTPS __m256 _mm256_mask_getmant_ps(__m256 s, __mmask8 k, __m256 a, enum intv, enum sgn);

VGETMANTPS __m256 _mm256_maskz_getmant_ps( __mmask8 k, __m256 a, enum intv, enum sgn);

VGETMANTPS __m128 _mm_getmant_ps( __m128 a, enum intv, enum sgn);

VGETMANTPS __m128 _mm_mask_getmant_ps(__m128 s, __mmask8 k, __m128 a, enum intv, enum sgn);

VGETMANTPS __m128 _mm_maskz_getmant_ps( __mmask8 k, __m128 a, enum intv, enum sgn);

SIMD Floating-Point Exceptions ¶

Denormal, Invalid

Other Exceptions ¶

See Exceptions Type E2.