RFR: 8281079: [s390] Unify Address Operand Encoding in Instruction Emitters

[Lutz Schmidt]

On Mon, 21 Feb 2022 14:11:26 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> May I please request reviews for this cleanup and unification change. It streamlines the address operand emitters for all instructions. As such, the modifications are widespread and may be cumbersome to review. Please ask questions if anything is unclear.
>> 
>> SAP does not maintain a full s390x build and test environment any longer. I would therefore very much appreciate if somebody would run a build and test cycle on s390x. 
>> 
>> As this is a s390x-only change, other platforms are not impacted.
>
> src/hotspot/cpu/s390/assembler_s390.inline.hpp line 1412:
> 
>> 1410:   int len_bits = instr >> (48-2);
>> 1411:   if (len_bits == 0) len_bits = instr >> (32-2);
>> 1412:   if (len_bits == 0) len_bits = instr >> (16-2);
> 
> Tricky, but looks correct.

Want some detailed comment here?

> src/hotspot/cpu/s390/assembler_s390.inline.hpp line 1423:
> 
>> 1421:       // The switch expression examines just the leftmost two bytes
>> 1422:       // of the main opcode. So the range of values is just [0..3].
>> 1423:       // Having a default clause makes the compiler happy.
> 
> A bit lengthy for a trivial explanation.

You mean I should not explain what's going on?

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PR: https://git.openjdk.java.net/jdk/pull/7324