RFR: 8283327: Add methods to save/restore registers when calling into the VM from C1/interpreter barrier code/improve push pop stuff for x86

[Erik Österlund]

On Fri, 18 Mar 2022 14:00:34 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   can I have reviews for this change that adds an API to save/restore caller-saved registers for VM upcalls for C1/interpreter.
> 
> Currently, for x86, this is done in a very ad-hoc (copy&pasty) way, which starts to fall apart. Additionally this fixes some problems with wrong stack alignment.
> 
> There is some cleanup to do separately to remove that copy&paste code in another CR. At the moment the API (`push_call_clobbered_registers/pop_call_clobbered_registers`) is only used for g1.
> 
> It's based on `RegSet` from AArch64.
> 
> Testing: tier1-5, tier1 testing with x64 and x86, with some at this point obscure combinations (like x86 UseSSE=0/1).
> 
> Thanks,
>   Thomas

src/hotspot/cpu/x86/macroAssembler_x86.cpp line 3599:

> 3597: #if defined(WINDOWS) && defined(_LP64)
> 3598:   XMMRegSet result = XMMRegSet::range(xmm0, xmm5);
> 3599:   if (FrameMap::get_num_caller_save_xmms() > 16) {

Why is this part needed?

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PR: https://git.openjdk.java.net/jdk/pull/7867