VCVTROPS2HF8S

VCVTROPS2HF8S is VCVTROPS2HF8 with saturation: each single is rounded to odd into E4M3, that is cut to 3 fraction bits with the last bit set if anything nonzero was cut, and packed into the low end of an xmm register under a write mask of one bit per byte. Where the result would be the NaN, from any single above 448 and from the infinities, it gives 448 (7Eh or FEh) with the single’s sign. A NaN still gives the NaN. The encoding is opcode 3Ah with the 66 prefix in EVEX map 5, W0, in AVX10_V2_AUX of the ACE specification; with F3 it is VCVTPS2HF8S, which rounds to nearest even.

Where saturation helps#

Without it, rounding to odd turns 449 into the NaN, since the odd neighbour of 448 is the NaN’s encoding. With it, every single from 448 up gives 448, as VCVTPS2HF8S does from 448 up. Below 448 the two round-to-odd forms agree: 1.0625 gives 1.125 (39h), and a normal single below 2^-9 gives 01h, the smallest denormal, ready for a narrowing to E2M1 with VCVTHF82BF4S. MXCSR is neither read nor written, and nothing is flagged.

In our builds#

GCC 14 and Clang 23 have no option for AVX10_V2_AUX: Clang 23’s assembler and GNU as 2.44 reject the mnemonic, and ACE’s intrinsic _mm512_cvtropss_hf8 is missing from Clang 23’s headers. This site’s recorded cases include none of VCVTROPS2HF8S.

Forms

Data flow

Where the elements of the sources go, element 0 on the right; results that depend on a control value are drawn for an example. How to read.

Operation

What the forms do, in pseudocode that our tests run against results recorded on real processors. How to read.

for i in range(VL // 32):
    if k1[i]:
        a = src2.f32[i]
        xmm1.hf8[i] = to_hf8s_odd(a)
    elif zeroing:
        xmm1.hf8[i] = 0
    # else: xmm1.hf8[i] keeps its value
for i in range(VL // 32, 16):
    xmm1.b[i] = 0
# m32bcst: src2.f32[i] is the m32 for every i
# HF8: to odd, denormals kept, no flags; MXCSR unused
# xmm1 is zeroed from bit 128 up

Operands

Flags

None: XED records no flag that the forms test or change.

Exceptions

The exception class is XED's name for the set of exception conditions that a form follows. How to read.

All forms

AVX512-E4

Attributes

What else XED records about the forms. How to read.

All forms

write masking

Memory forms

embedded broadcast (tuple Full); memory fault suppression

CPUID and processors

Each form belongs to an XED ISA set. A form can be used when the processor reports every CPUID bit of one of its ISA set's alternatives.

More AVX10_V2_AUX instructions

• VCVTBF42HF8
• VCVTBF62HF8
• VCVTBF82BF4S
• VCVTBF82BF6S
• VCVTBF82PS
• VCVTBIASPS2BF8
• VCVTBIASPS2BF8S
• VCVTBIASPS2HF8
• VCVTBIASPS2HF8S
• VCVTHF62HF8
• VCVTHF82BF4S
• VCVTHF82HF6S
• VCVTHF82PS
• VCVTPS2BF8
• VCVTPS2BF8S
• VCVTPS2HF8
• VCVTPS2HF8S
• VCVTROPS2HF8
• VPMOVSSDB
• VUNPACKB