VRCPSH—Compute Reciprocal of Scalar FP16 Value

Opcode/Instruction Op/En 64/32 bit Mode Support CPUID Feature Flag Description
EVEX.LLIG.66.MAP6.W0 4D /r VRCPSH xmm1{k1}{z}, xmm2, xmm3/m16 A V/V AVX512-FP16 Compute the approximate reciprocal of the low FP16 value in xmm3/m16 and store the result in xmm1 subject to writemask k1. Bits 127:16 from 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


This instruction performs a SIMD computation of the approximate reciprocal of the low FP16 value in the second source operand (the third operand) and stores the result in the low word element of the destination operand (the first operand) according to the writemask k1. Bits 127:16 of the XMM register destination are copied from corre-sponding bits in the first source operand (the second operand). The maximum relative error for this approximation is less than 2−11 + 2−14.

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.

For special cases, see Table 5-18.


VRCPSH dest{k1}, src1, src2

IF k1[0] or *no writemask*:

DEST.fp16[0] := APPROXIMATE(1.0 / src2.fp16[0])

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

VRCPSH __m128h _mm_mask_rcp_sh (__m128h src, __mmask8 k, __m128h a, __m128h b);

VRCPSH __m128h _mm_maskz_rcp_sh (__mmask8 k, __m128h a, __m128h b);

VRCPSH __m128h _mm_rcp_sh (__m128h a, __m128h b);

SIMD Floating-Point Exceptions


Other Exceptions

EVEX-encoded instruction, see Table 2-58, “Type E10 Class Exception Conditions.”