RFR: 8258134: assert(size == calc_size) failed: incorrect size calculation on x86_32 with AVX512 machines

[Nils Eliasson]

On Fri, 11 Dec 2020 23:56:15 GMT, Jie Fu <jiefu at openjdk.org> wrote:

> Hi all,
> 
> Two vector api tests crashed on x86_32 with AVX512 machines due to this assert [1].
> The reason is that 'calc_size' is incorrect.
> 
> But there is no need to calculate 'calc_size' manually at all since the result [2] is actually never used by the VM.
> Also, it is really hard to maintain the calculation logic for various hardwares and configurations.
> And it may be easily broken again in the future with more and more complicated instructions & configurations.
> 
> So it would be better to remove the calculation and the assert, which is safe and already done for x86_64 [3].
> The fix just follows what is done for x86_64.
> 
> Thanks.
> Best regards,
> Jie
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/x86_32.ad#L1016
> [2] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/x86_32.ad#L1059
> [3] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/x86_64.ad#L1042

Changes requested by neliasso (Reviewer).

src/hotspot/cpu/x86/x86_32.ad line 1062:

> 1060:       int src_offset = ra_->reg2offset(src_first);
> 1061:       int dst_offset = ra_->reg2offset(dst_first);
> 1062:       vec_stack_to_stack_helper(cbuf, src_offset, dst_offset, ireg, st);

None of these functions (vec_stack_to_stack_helper, vec_mov_helper, vec_spill_helper, vec_spill_helper) returns a value that is used on either x86 or x64 now. 

Please make them all return void.

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PR: https://git.openjdk.java.net/jdk/pull/1753