RFR: 8289552: Make intrinsic conversions between bit representations of half precision values and floats [v7]

[Sandhya Viswanathan]

On Thu, 1 Sep 2022 23:22:46 GMT, Smita Kamath <svkamath at openjdk.org> wrote:

>> 8289552: Make intrinsic conversions between bit representations of half precision values and floats
>
> Smita Kamath has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Added missing parantheses

Some minor naming/formatting comments. Rest of the patch looks good to me.

src/hotspot/share/runtime/sharedRuntime.cpp line 487:

> 485:   jshort signif_bits = (jshort)(f_signif_bits >> (13 + exp_delta));
> 486: 
> 487:   jint lsb = (f_signif_bits & (1 << 13 + exp_delta));

It will be more clear to have the parenthesis like this:
jint lsb = f_signif_bits & (1 << (13 + exp_delta));

src/hotspot/share/runtime/sharedRuntime.cpp line 522:

> 520: 
> 521:   // Add the bias of float exponent and shift
> 522:   int float_exp_bits = ((hf_exp + 127) << 24 - 1);

It will be more clear to have the parenthesis like this:
int float_exp_bits = (hf_exp + 127) << (24 - 1);

May be we should refer to src/java.base/share/classes/java/lang/Float.java:floatToFloat16 and Float16toFloat in comments.

src/hotspot/share/runtime/sharedRuntime.cpp line 525:

> 523: 
> 524:   // Combine sign, exponent and significand bits
> 525:   return (jfloat) ((hf_sign_bit << 16) | float_exp_bits | (hf_significand_bits << significand_shift));

You could call SharedRuntime::i2f here as well to be consistent to line 517.

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PR: https://git.openjdk.org/jdk/pull/9781