RFR: 8256061: RegisterSaver::save_live_registers() omits upper halves of ZMM0-15 registers

[Sandhya Viswanathan]

On Mon, 9 Nov 2020 21:34:26 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> It looks like the upper 256 bits of ZMM0-15 are already being saved as part of the following statements in sharedRuntime_x86_64.cpp:
>>  191   if (save_vectors) {
>>  192     // Save upper half of YMM registers(0..15)
>>  193     int base_addr = XSAVE_AREA_YMM_BEGIN;
>>  194     for (int n = 0; n < 16; n++) {
>>  195       __ vextractf128_high(Address(rsp, base_addr+n*16), as_XMMRegister(n));
>>  196     }
>>  197     if (VM_Version::supports_evex()) {
>>  198       // Save upper half of ZMM registers(0..15)
>>  199       base_addr = XSAVE_AREA_ZMM_BEGIN;
>>  200       for (int n = 0; n < 16; n++) {
>>  201         __ vextractf64x4_high(Address(rsp, base_addr+n*32), as_XMMRegister(n));
>>  202       }
>>  203       // Save full ZMM registers(16..num_xmm_regs)
>>  204       base_addr = XSAVE_AREA_UPPERBANK;
>>  205       off = 0;
>>  206       int vector_len = Assembler::AVX_512bit;
>>  207       for (int n = 16; n < num_xmm_regs; n++) {
>>  208         __ evmovdqul(Address(rsp, base_addr+(off++*64)), as_XMMRegister(n), vector_le
>>      n);
>>  209       }
>>  210     }
>>  211   }
>
> Thanks for the correction, Sandhya. 
> You are absolutely right that the values are already saved. 
> The problem is the `OopMap` doesn't reflect that and the patch fixes that.

Thanks for the clarification, the changes looks good to me.

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PR: https://git.openjdk.java.net/jdk/pull/1131