VGETEXPSH — Convert Exponents of Scalar FP16 Values to FP16 Values

Instruction En Bit Mode Flag Support Instruction En Bit Mode Flag Support 64/32 CPUID Feature Instruction En Bit Mode Flag CPUID Feature Instruction En Bit Mode Flag Op/ 64/32 CPUID Feature Instruction En Bit Mode Flag 64/32 CPUID Feature Instruction En Bit Mode Flag CPUID Feature Instruction En Bit Mode Flag Op/ 64/32 CPUID Feature		Support		Description
EVEX.LLIG.66.MAP6.W0 43 /r VGETEXPSH xmm1{k1}{z}, xmm2, xmm3/m16 {sae}	A	V/V	AVX512-FP16	Convert the exponent of FP16 values in the low word of the source operand to FP16 results representing unbiased integer exponents, and stores the results in the low word of the destination register subject to writemask k1. Bits 127:16 of xmm2 are copied to xmm1[127:16].

Instruction Operand Encoding ¶

Op/En	Tuple	Operand 1	Operand 2	Operand 3	Operand 4
A	Scalar	ModRM:reg (w)	VEX.vvvv (r)	ModRM:r/m (r)	N/A

Description ¶

This instruction extracts the biased exponents from the normalized FP16 representation of the low word element of the source operand (the second operand) as unbiased signed integer value, or convert the denormal representation of input data to an unbiased negative integer value. The integer value of the unbiased exponent is converted to an FP16 value and written to the low word element of the destination operand (the first operand) as an FP16 number.

Bits 127:16 of the destination operand are copied from the corresponding bits of the first source operand. Bits MAXVL-1:128 of the destination operand are zeroed. The low FP16 element of the destination is updated according to the writemask.

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 5-16.

The formula is:

GETEXP(x) = floor(log₂(|x|))

Notation floor(x) stands for maximal integer not exceeding real number x.

Software usage of VGETEXPxx and VGETMANTxx instructions generally involve a combination of GETEXP operation and GETMANT operation (see VGETMANTSH). Thus, the VGETEXPSH instruction does not require software to handle SIMD floating-point exceptions.

Operation ¶

VGETEXPSH dest{k1}, src1, src2 ¶

IF k1[0] or *no writemask*:
    DEST.fp16[0] := getexp_fp16(src2.fp16[0]) // see VGETEXPPH
ELSE IF *zeroing*:
    DEST.fp16[0] := 0
//else DEST.fp16[0] remains unchanged
DEST[127:16] := src1[127:16]
DEST[MAXVL-1:128] := 0

Intel C/C++ Compiler Intrinsic Equivalent ¶

VGETEXPSH __m128h _mm_getexp_round_sh (__m128h a, __m128h b, const int sae);

VGETEXPSH __m128h _mm_mask_getexp_round_sh (__m128h src, __mmask8 k, __m128h a, __m128h b, const int sae);

VGETEXPSH __m128h _mm_maskz_getexp_round_sh (__mmask8 k, __m128h a, __m128h b, const int sae);

VGETEXPSH __m128h _mm_getexp_sh (__m128h a, __m128h b);

VGETEXPSH __m128h _mm_mask_getexp_sh (__m128h src, __mmask8 k, __m128h a, __m128h b);

VGETEXPSH __m128h _mm_maskz_getexp_sh (__mmask8 k, __m128h a, __m128h b);

SIMD Floating-Point Exceptions ¶

Invalid, Denormal

Other Exceptions ¶

EVEX-encoded instructions, see Table 2-47, “Type E3 Class Exception Conditions.”