RFR: 8349686: [s390x] C1: Improve Class.isInstance intrinsic [v7]

[Amit Kumar]

On Fri, 14 Feb 2025 10:28:34 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Amit Kumar has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   space for 3 registers
>
> src/hotspot/cpu/s390/c1_Runtime1_s390.cpp line 643:
> 
>> 641:       __ z_stg(temp3 /*Z_R11*/, 1*BytesPerWord + frame::z_abi_160_size, Z_SP);
>> 642:       assert(2*BytesPerWord + frame::z_abi_160_size == frame_size, "check");
>> 643: 
> 
> I think you may be able temporarily to save R10 and R11 in the floating-point registers. You have plenty of call-clobbered FP registers, I think. This might work better than creating a stack frame. I guess it's possible to copy from an integer register to a floating-point register without altering any of the bits. There might be no performance advantage, but I think that it's worth a try.

I see some further improvements. I will post the result down.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23535#discussion_r1956275664