RFR: JDK-8241503: C2: Share MacroAssembler between mach nodes during code emission

[Amit Kumar]

On Thu, 2 Nov 2023 22:17:43 GMT, Cesar Soares Lucas <cslucas at openjdk.org> wrote:

> # Description
> 
> Please review this PR with a patch to re-use the same C2_MacroAssembler object to emit all instructions in the same compilation unit.
> 
> Overall, the change is pretty simple. However, due to the renaming of the variable to access C2_MacroAssembler, from `_masm.` to `masm->`, and also some method prototype changes, the patch became quite large.
> 
> # Help Needed for Testing
> 
> I don't have access to all platforms necessary to test this. I hope some other folks can help with testing on `S390`, `RISC-V` and `PPC`.

`s390x` also run into assert failure: `assert(masm->inst_mark() == nullptr) failed: should be.`


V  [libjvm.so+0xfb0938]  PhaseOutput::fill_buffer(C2_MacroAssembler*, unsigned int*)+0x2370  (output.cpp:1812)
V  [libjvm.so+0xfb21ce]  PhaseOutput::Output()+0xcae  (output.cpp:362)
V  [libjvm.so+0x6a90a8]  Compile::Code_Gen()+0x460  (compile.cpp:2989)
V  [libjvm.so+0x6ad848]  Compile::Compile(ciEnv*, ciMethod*, int, Options, DirectiveSet*)+0x1738  (compile.cpp:887)
V  [libjvm.so+0x4fb932]  C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x14a  (c2compiler.cpp:119)
V  [libjvm.so+0x6b81a2]  CompileBroker::invoke_compiler_on_method(CompileTask*)+0xd9a  (compileBroker.cpp:2282)
V  [libjvm.so+0x6b8eaa]  CompileBroker::compiler_thread_loop()+0x5a2  (compileBroker.cpp:1943)

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PR Comment: https://git.openjdk.org/jdk/pull/16484#issuecomment-1801070622