Can we dump more pretty CFG file format for C1 compiler HIR

[Vladimir Ivanov]

(BCCing hotspot-dev)

> `+XX:+PrintCFGToFile` could dump ssa-based HIR into file, but its format is messy:```cfg
>      begin_states
>        begin_locals
>          size 3
>          method "static jint com.github.kelthuzadx.HelloWorld.jerkSum(jint)"
>   1  i7 "[R570|I]"
>        end_locals
>      end_states
>      begin_HIR
> .22 0 i15 ireturn i7 <|@
>      end_HIR
>      begin_LIR
>    42 label [label:0x000002136a396400] <|@
>    44 move [R570|I] [rax|I]  <|@
>    46 return [rax|I]   <|@
>      end_LIR
>    end_block
> end_cfg
> begin_intervals
>    name "Before Register Allocation"
> 3 fixed "[rax|I]" 3 570 [0, 1[ [44, 46[  "no spill store"
> 4 fixed "[rdx|I]" 4 -1 [0, 4[  "no definition"
> 569 int 569 4 [4, 10[ 4 M 10 S  "no spill store"
> 570 int 570 569 [10, 26[ [38, 44[ 10 M 26 S 38 M 41 L 44 S  "no optimization"
> 571 int 571 573 [12, 30[ [36, 42[ 12 M 18 M 28 S 30 S 36 M 41 L  "no optimization"
> 572 int 572 570 [26, 38[ 26 M 28 M 38 S  "no spill store"
> 573 int 573 571 [30, 36[ 30 M 32 M 36 S  "no spill store"
> end_intervals
> 
> 
> ```
> So can we produce more readable format?

Do you have any particular format in mind or just looking for something 
more readable? Are you satisfied with what -XX:+PrintIR [1] / 
-XX:+PrintLIR [2] produce?

BTW it is confusing to see -XX:+PrintCFGToFile dumping HIR/LIR info as 
well when -XX:+PrintCFG dumps exclusively CFG.

Best regards,
Vladimir Ivanov

[1] -XX:+PrintIR
IR after parsing
B1 [0, 0] -> B0 sux: B0
empty stack
inlining depth 0
__bci__use__tid____instr____________________________________
. 0    0     13    std entry B0

B0 (SV) [0, 12] pred: B1
empty stack
inlining depth 0
__bci__use__tid____instr____________________________________
   0    0    a5     <instance 0x00007f84fed9c2c0 
klass=jdk/internal/misc/Unsafe>
   4    0    l7     16L
. 9    0    i8     compareAndSetLong(a1, l7, l2, l3)
   12   0    i9     1
   12   0    i10    i8 & i9
. 12   0    i11    ireturn i10


[2] -XX:+PrintLIR
LIR:
B1 [0, 0] sux: B0
__id_Instruction___________________________________________
    0 label [label:0x00007ffd2688a6c0]
    2 std_entry

B0 std [0, 12] preds: B1
__id_Instruction___________________________________________
   12 label [label:0x00007ffd268895e0]
   14 leal [Base:[rsi|L] Disp: 16|J] [rsirsi|J]
   16 move [rdxrdx|J] [raxrax|J]
   18 move [rcxrcx|J] [rbxrbx|J]
   20 cas_long [rsirsi|J] [raxrax|J] [rbxrbx|J]
   22 cmove [EQ] [int:1|I] [int:0|I] [rax|I]
   26 logic_and [rax|I] [int:1|I] [rax|I]
   30 return [rax|I]