RFR: 8294588: Auto vectorize half precision floating point conversion APIs [v5]

[Smita Kamath]

On Tue, 6 Dec 2022 23:34:40 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> src/hotspot/cpu/x86/assembler_x86.cpp line 1958:
>> 
>>> 1956:   InstructionMark im(this);
>>> 1957:   InstructionAttr attributes(vector_len, /* rex_w */ false, /* legacy_mode */ false, /* no_mask_reg */ true, /*uses_vl */ true);
>>> 1958:   attributes.set_address_attributes(/* tuple_type */ EVEX_HVM, /* input_size_in_bits */ EVEX_NObit);
>> 
>> Is it correct to set `EVEX_*` attributes in case EVEX is switched off (by `UseAVX` flag)?
>
> Or a CPU supports F16C but does not EVEX (avx512f).

Hi Vladimir, we have a prior example of vpaddb instruction where these attributes are set. The assembler will ignore these attributes if UseAVX < 3.

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PR: https://git.openjdk.org/jdk/pull/11471