VCVTSS2SH

Convert Low FP

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.NP.MAP5.W0 1D /r VCVTSS2SH xmm1{k1}{z}, xmm2, xmm3/m32 {er}	A	V/V	AVX512-FP16	Convert low FP32 value in xmm3/m32 to an FP16 value and store in the low element of 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

Description

This instruction converts the low FP32 value in the second source operand to a FP16 value in the low element of the destination operand.

When the conversion is inexact, the value returned is rounded according to the rounding control bits in the MXCSR register.

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.

Operation

VCVTSS2SH dest, src1, src2

IF *SRC2 is a register* and (EVEX.b = 1):
    SET_RM(EVEX.RC)
ELSE:
    SET_RM(MXCSR.RC)
IF k1[0] OR *no writemask*:
    DEST.fp16[0] := Convert_fp32_to_fp16(SRC2.fp32[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

VCVTSS2SH __m128h _mm_cvt_roundss_sh (__m128h a, __m128 b, const int rounding);

VCVTSS2SH __m128h _mm_mask_cvt_roundss_sh (__m128h src, __mmask8 k, __m128h a, __m128 b, const int rounding);

VCVTSS2SH __m128h _mm_maskz_cvt_roundss_sh (__mmask8 k, __m128h a, __m128 b, const int rounding);

VCVTSS2SH __m128h _mm_cvtss_sh (__m128h a, __m128 b);

VCVTSS2SH __m128h _mm_mask_cvtss_sh (__m128h src, __mmask8 k, __m128h a, __m128 b);

VCVTSS2SH __m128h _mm_maskz_cvtss_sh (__mmask8 k, __m128h a, __m128 b);

SIMD Floating-Point Exceptions

Invalid, Underflow, Overflow, Precision, Denormal.

Other Exceptions

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

This UNOFFICIAL, mechanically-separated, non-verified reference is provided for convenience, but it may be incomplete or broken in various obvious or non-obvious ways. Refer to Intel® 64 and IA-32 Architectures Software Developer’s Manual for anything serious.