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Henk-Jan Lebbink edited this page Jun 5, 2018 · 13 revisions

VFPCLASSPS — Tests Types Of a Packed Float32 Values

Opcode/ Instruction Op / En 64/32 bit Mode Support CPUID Feature Flag Description
EVEX.128.66.0F3A.W0 66 /r ib VFPCLASSPS k2 {k1}, xmm2/m128/m32bcst, imm8 A V/V AVX512VL AVX512DQ Tests the input for the following categories: NaN, +0, -0, +Infinity, -Infinity, denormal, finite negative. The immediate field provides a mask bit for each of these category tests. The masked test results are OR-ed together to form a mask result.
EVEX.256.66.0F3A.W0 66 /r ib VFPCLASSPS k2 {k1}, ymm2/m256/m32bcst, imm8 A V/V AVX512VL AVX512DQ Tests the input for the following categories: NaN, +0, -0, +Infinity, -Infinity, denormal, finite negative. The immediate field provides a mask bit for each of these category tests. The masked test results are OR-ed together to form a mask result.
EVEX.512.66.0F3A.W0 66 /r ib VFPCLASSPS k2 {k1}, zmm2/m512/m32bcst, imm8 A V/V AVX512DQ Tests the input for the following categories: NaN, +0, -0, +Infinity, -Infinity, denormal, finite negative. The immediate field provides a mask bit for each of these category tests. The masked test results are OR-ed together to form a mask result.

Instruction Operand Encoding

Op/En Tuple Type Operand 1 Operand 2 Operand 3 Operand 4
A Full ModRM:reg (w) ModRM:r/m (r) NA NA

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

#UD If EVEX.vvvv != 1111B.

Source: Intel® Architecture Software Developer's Manual (May 2018)
Generated: 5-6-2018

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