RFR: 8285487: Do not generate trampolines for runtime calls if they are not needed [v3]

[Andrew Haley]

On Thu, 28 Apr 2022 21:55:25 GMT, Evgeny Astigeevich <duke at openjdk.java.net> wrote:

>> [JDK-8280872](https://bugs.openjdk.java.net/browse/JDK-8280872) put the non-nmethod segment between two others. It made trampolines for runtime calls redundant in most cases.
>> 
>> This PR uses `target_needs_far_branch()` for runtime calls to check whether they need trampolines. Trampolines are not generated if they are not needed.
>> 
>> Testing:
>> - `tier1`...`tier4`: Passed
>> - `compiler/c2/aarch64/TestTrampoline.java`: Passed
>> 
>> Note: `compiler/c2/aarch64/TestTrampoline.java` requires the release build. This is because debug builds have the branch range set to 2M which causes always generation of trampolines.
>
> Evgeny Astigeevich has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Move code of target_needs_trampoline inside trampoline_call

src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 579:

> 577:   // when a new callee address out of 128M range.
> 578:   bool need_trampoline = (entry.rspec().type() == relocInfo::runtime_call_type) ?
> 579:       target_needs_far_branch(entry.target()) : far_branches();

This is all very confusing too. Can't `target_needs_far_branch()` handle all cases? So we don't need a conditional expression here.

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PR: https://git.openjdk.java.net/jdk/pull/8403