RFR 8222243 [lworld] Calling convention - C2 to C1 (fixed point params only)

[Tobias Hartmann]

Hi Ioi,

this looks good to me.

Thanks,
Tobias

On 10.04.19 07:56, Ioi Lam wrote:
> https://bugs.openjdk.java.net/browse/JDK-8222243
> http://cr.openjdk.java.net/~iklam/valhalla/8222243-c2-calls-c1-fixed-point-params.v01/
> 
> Implement Method::verified_entry and Method::verified_value_ro_entry for C1-compiled methods. This
> allows C2 to call C1 with scalarized parameters.
> 
> In this RFR, we only support passing of fixed point parameters (boolean, byte, char, short, int and
> long), along with value objects that contain fields of these types. Support for other types of
> parameters/fields will be implemented in subsequent steps.
> 
> The C1 code uses the same functionality as the code in sharedRuntime.cpp that handles the signature
> of the different compiled entries. Hence, I refactored the code into a new class
> CompiledEntrySignature.
> 
> The code is littered with lots of FIXME (no support for floats, oops, GC, etc). I intend to fix
> those soon.
> 
> Thanks
> - Ioi
> 
> --------------------------------------------------
> 
> Example of parameter shuffling in C1 verified_entry
> 
> static void test(int a, Point p, int b) {...}
> 
> C2 passes outgoing parameters as
> 
>   # parm0:    rsi       = int a
>   # parm1:    rdx       = int p.x
>   # parm2:    rcx       = int p.y
>   # parm3:    r8        = int b
> 
> 
> C1 expects incoming parameters as
> 
>   # parm0:    rsi       = int   a
>   # parm1:    rdx       = Point p
>   # parm2:    rcx       = int   b
> 
> 
> The C1 Verified Entry Point will pack the scalarized parameters (p.x,
> p.y) back into a Point reference, and shuffle the rest of the params:
> 
>     0: push   %rbp
>     1: sub    $0x30,%rsp
>     5: mov    $0x7f0b154f9448,%rbx  ; Method test(IQPoint;I)
>    15: callq  0x00007f0b4c7d2cc0    ;  {runtime_call buffer_value_args}
>                                     ;  no need to shuffle rsi (a)
>    20: mov    0x10(%rax),%r11d
>    24: shl    $0x3,%r11             ;  r11 = p
>    28: mov    %edx,0x10(%r11)       ;  set p.x
>    32: mov    %ecx,0x14(%r11)       ;  set p.y
>    36: mov    %r11,%rdx             ;  rdx = p
>    39: mov    %r8,%rcx              ;  rcx = a
>    42: pop    %rbp
>    43: add    $0x30,%rsp
>    47: jmpq   verified_value_entry
> 
> 
> 
>