VGETMANTPH — Extract FP16 Vector of Normalized Mantissas from FP16 Vector

Instruction Operand Encoding ¶

Description ¶

This instruction converts the FP16 values in the source operand (the second operand) to FP16 values with the mantissa normalization and sign control specified by the imm8 byte, see Table 5-19. 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 elements are updated according to the writemask.

For each input FP16 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 the sign control and the source sign and the leading fraction bit.

The encoded value of imm8[1:0] and sign control are shown in Table 5-19.

Each converted FP16 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 5-20 when dealing with floating-point special numbers.

1. In case SC[1]==0, the sign of Getmant(SRC) is declared according to SC[0].

Operation ¶

def getmant_fp16(src, sign_control, normalization_interval):
    bias := 15
    dst.sign := sign_control[0] ? 0 : src.sign
    signed_one := sign_control[0] ? +1.0 : -1.0
    dst.exp := src.exp
    dst.fraction := src.fraction
    zero := (dst.exp = 0) and (dst.fraction = 0)
    denormal := (dst.exp = 0) and (dst.fraction != 0)
    infinity := (dst.exp = 0x1F) and (dst.fraction = 0)
    nan := (dst.exp = 0x1F) and (dst.fraction != 0)
    src_signaling := src.fraction[9]
    snan := nan and (src_signaling = 0)
    positive := (src.sign = 0)
    negative := (src.sign = 1)
    if nan:
        if snan:
            MXCSR.IE := 1
        return qnan(src)
    if positive and (zero or infinity):
        return 1.0
    if negative:
        if zero:
            return signed_one
        if infinity:
            if sign_control[1]:
                MXCSR.IE := 1
                return QNaN_Indefinite
            return signed_one
        if sign_control[1]:
            MXCSR.IE := 1
            return QNaN_Indefinite
    if denormal:
        jbit := 0
        dst.exp := bias // set exponent to bias value
        while jbit = 0:
            jbit := dst.fraction[9]
            dst.fraction := dst.fraction << 1
            dst.exp : = dst.exp - 1
        MXCSR.DE := 1
    unbaiased_exp := dst.exp - bias
    odd_exp := unbaiased_exp[0]
    signaling_bit := dst.fraction[9]
    if normalization_interval = 0b00:
        dst.exp := bias
    else if normalization_interval = 0b01:
        dst.exp := odd_exp ? bias-1 : bias
    else if normalization_interval = 0b10:
        dst.exp := bias-1
    else if normalization_interval = 0b11:
        dst.exp := signaling_bit ? bias-1 : bias
    return dst

VGETMANTPH dest{k1}, src, imm8 ¶

VL = 128, 256 or 512
KL := VL/16
sign_control := imm8[3:2]
normalization_interval := imm8[1:0]
FOR i := 0 to KL-1:
    IF k1[i] or *no writemask*:
        IF SRC is memory and (EVEX.b = 1):
            tsrc := src.fp16[0]
        ELSE:
            tsrc := src.fp16[i]
        DEST.fp16[i] := getmant_fp16(tsrc, sign_control, normalization_interval)
    ELSE IF *zeroing*:
        DEST.fp16[i] := 0
    //else DEST.fp16[i] remains unchanged
DEST[MAXVL-1:VL] := 0

Intel C/C++ Compiler Intrinsic Equivalent ¶

VGETMANTPH __m128h _mm_getmant_ph (__m128h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign);

VGETMANTPH __m128h _mm_mask_getmant_ph (__m128h src, __mmask8 k, __m128h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign);

VGETMANTPH __m128h _mm_maskz_getmant_ph (__mmask8 k, __m128h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign);

VGETMANTPH __m256h _mm256_getmant_ph (__m256h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign);

VGETMANTPH __m256h _mm256_mask_getmant_ph (__m256h src, __mmask16 k, __m256h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign);

VGETMANTPH __m256h _mm256_maskz_getmant_ph (__mmask16 k, __m256h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign);

VGETMANTPH __m512h _mm512_getmant_ph (__m512h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign);

VGETMANTPH __m512h _mm512_mask_getmant_ph (__m512h src, __mmask32 k, __m512h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign);

VGETMANTPH __m512h _mm512_maskz_getmant_ph (__mmask32 k, __m512h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign);

VGETMANTPH __m512h _mm512_getmant_round_ph (__m512h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign, const int sae);

VGETMANTPH __m512h _mm512_mask_getmant_round_ph (__m512h src, __mmask32 k, __m512h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign, const int sae);

VGETMANTPH __m512h _mm512_maskz_getmant_round_ph (__mmask32 k, __m512h a, _MM_MANTISSA_NORM_ENUM norm, _MM_MANTISSA_SIGN_ENUM sign, const int sae);

SIMD Floating-Point Exceptions ¶

Invalid, Denormal.

Other Exceptions ¶

EVEX-encoded instructions, see Table 2-46, “Type E2 Class Exception Conditions.”