On Tue, 7 Sep 2021 22:31:30 GMT, Smita Kamath <[email protected]> wrote:

> Performance dropped up to 10% for 1k data after 8267125 for CPUs that do not 
> support the new intrinsic. Tests run were crypto.full.AESGCMBench and 
> crypto.full.AESGCMByteBuffer from the jmh micro benchmarks.
> 
> The problem is each instance of GHASH allocates 96 extra longs for the 
> AVX512+VAES intrinsic regardless if the intrinsic is used. This extra table 
> space should be allocated differently so that non-supporting CPUs do not 
> suffer this penalty. This issue also affects non-Intel CPUs too.

src/hotspot/share/opto/library_call.cpp line 6796:

> 6794: 
> 6795:   Node* avx512_subkeyHtbl = new_array(klass_node, intcon(96), 0);
> 6796:   if (avx512_subkeyHtbl == NULL) return false;

This looks very Intel-specific, but it's in generic code. Please make this 
constant 96 a symbol and push it into a header file in the x86 back end.

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PR: https://git.openjdk.java.net/jdk/pull/5402

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