RFR: 8302369: Reduce the stack size of the C1 compiler

[Andrew Haley]

On Tue, 14 Feb 2023 03:45:04 GMT, SUN Guoyun <duke at openjdk.org> wrote:

> The current fact is that C1 uses more stack space than the C2 compiler, taking method `java.lang.Object::<init>`as an example on the x86_64 platform , the stack size used is 48 bytes for C1 compiler, while only 16 bytes is used for C2 compiler.
> 
> ========== C1-compiled nmethod =====
> 0x00007f93311cc747: push %rbp
> 0x00007f93311cc748: sub $0x30,%rsp // stack sizes is 48 bytes
> 
> 
> ========== C2-compiled nmethod =======
>     pushq rbp # Save rbp
>     subq rsp, #16 # Create frame //stack sizes is 16 bytes
> 
> After this patch, the C1 compiler will use less stack space. also taking method `java.lang.Object::<init>`as an example on the x86_64 platform , the stack size used is 16 bytes, which is the same as C2 compiler.
> 
> ========== C1-compiled nmethod =====
> 0x00007f80491ce647:   push   %rbp
> 0x00007f80491ce648:   sub    $0x10,%rsp   //stack sizes is 16 bytes

src/hotspot/share/c1/c1_FrameMap.cpp line 165:

> 163:   _num_monitors = monitors;
> 164:   assert(reserved_argument_area_size >= 0, "not set");
> 165:   _reserved_argument_area_size = MAX2(4, reserved_argument_area_size) * BytesPerWord;

This line probably deserves a comment.

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PR: https://git.openjdk.org/jdk/pull/12548