VFPCLASSPS — Tests Types Of a Packed Float32 Values

Instruction Operand Encoding ¶

Description ¶

The FPCLASSPS instruction checks the packed single-precision floating point values for special categories, specified by the set bits in the imm8 byte. Each set bit in imm8 specifies a category of floating-point values that the input data element is classified against. The classified results of all specified categories of an input value are ORed together to form the final boolean result for the input element. The result of each element is written to the corresponding bit in a mask register k2 according to the writemask k1. Bits [MAX_KL-1:16/8/4] of the destination are cleared.

The classification categories specified by imm8 are shown in Figure 5-13. The classification test for each category is listed in Table 5-13.

The 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 32-bit memory location.

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

Operation ¶

CheckFPClassSP (tsrc[31:0], imm8[7:0]){
    //* Start checking the source operand for special type *//
    NegNum ←tsrc[31];
    IF (tsrc[30:23]=0FFh) Then ExpAllOnes←1; FI;
    IF (tsrc[30:23]=0h) Then ExpAllZeros←1;
    IF (ExpAllZeros AND MXCSR.DAZ) Then
        MantAllZeros ← 1;
    ELSIF (tsrc[22:0]=0h) Then
        MantAllZeros ← 1;
    FI;
    ZeroNumber= ExpAllZeros AND MantAllZeros
    SignalingBit= tsrc[22];
    sNaN_res←ExpAllOnes AND NOT(MantAllZeros) AND NOT(SignalingBit); // sNaN
    qNaN_res←ExpAllOnes AND NOT(MantAllZeros) AND SignalingBit; // qNaN
    Pzero_res←NOT(NegNum) AND ExpAllZeros AND MantAllZeros; // +0
    Nzero_res←NegNum AND ExpAllZeros AND MantAllZeros; // -0
    PInf_res←NOT(NegNum) AND ExpAllOnes AND MantAllZeros; // +Inf
    NInf_res←NegNum AND ExpAllOnes AND MantAllZeros; // -Inf
    Denorm_res←ExpAllZeros AND NOT(MantAllZeros); // denorm
    FinNeg_res←NegNum AND NOT(ExpAllOnes) AND NOT(ZeroNumber); // -finite
    bResult = ( imm8[0] AND qNaN_res ) OR (imm8[1] AND Pzero_res ) OR
            ( imm8[2] AND Nzero_res ) OR ( imm8[3] AND PInf_res ) OR
            ( imm8[4] AND NInf_res ) OR ( imm8[5] AND Denorm_res ) OR
            ( imm8[6] AND FinNeg_res ) OR ( imm8[7] AND sNaN_res );
    Return bResult;
} //* end of CheckSPClassSP() *//

VFPCLASSPS (EVEX encoded versions) ¶

(KL, VL) = (4, 128), (8, 256), (16, 512)
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[j]←CheckFPClassDP(SRC1[31:0], imm8[7:0]);
                ELSE
                    DEST[j]←CheckFPClassDP(SRC1[i+31:i], imm8[7:0]);
            FI;
        ELSE DEST[j]←0 ; zeroing-masking only
    FI;
ENDFOR
DEST[MAX_KL-1:KL] ← 0

Intel C/C++ Compiler Intrinsic Equivalent ¶

VFPCLASSPS __mmask16 _mm512_fpclass_ps_mask( __m512 a, int c);

VFPCLASSPS __mmask16 _mm512_mask_fpclass_ps_mask( __mmask16 m, __m512 a, int c)

VFPCLASSPS __mmask8 _mm256_fpclass_ps_mask( __m256 a, int c)

VFPCLASSPS __mmask8 _mm256_mask_fpclass_ps_mask( __mmask8 m, __m256 a, int c)

VFPCLASSPS __mmask8 _mm_fpclass_ps_mask( __m128 a, int c)

VFPCLASSPS __mmask8 _mm_mask_fpclass_ps_mask( __mmask8 m, __m128 a, int c)

SIMD Floating-Point Exceptions ¶

None

Other Exceptions ¶

See Exceptions Type E4