RFR: 8287373: remove unnecessary paddings in generated code

[Vladimir Kozlov]

On Tue, 7 Jun 2022 20:41:04 GMT, Boris Ulasevich <bulasevich at openjdk.org> wrote:

>> src/hotspot/cpu/x86/sharedRuntime_x86_32.cpp line 2635:
>> 
>>> 2633:   // allocate space for the code
>>> 2634:   // setup code generation tools
>>> 2635:   CodeBuffer   buffer("handler_blob", 2048, 1024);
>> 
>> Why you need to double the size?
>
> I did it to fix the CodeBuffer overflow assert on x86 build. SharedRuntime::generate_handler_blob asks a 1KB buffer -
> actually CodeBuffer::initialize reserves the given size with some extra bytes; with the new formula (code_size + align + slop * SECT_LIMIT) the extra bytes number is reduced, causing the handler_blob generator buffer to overflow. My solution is to double the code_size estimate for handler_blob generator buffer. The same 2048/1024 numbers we can see on other platforms - aarch, pcc, amd, riscv.

okay

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PR: https://git.openjdk.java.net/jdk/pull/8453