What this mean "dead: 1" and "dead: 0 1" on each tb block start?

What this mean "dead: 1" and "dead: 0 1" on each tb block start?

[tugouxp]

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HI folks:
  on each tb block start, there are following ir code, and the most confusing me is that  the postfix of each line "dead:" flag, what it is represent precisely?
i guess it may be related to the register or varible liveness for help generating tghe target machine code, but i cant get the precisely connection of the dead attrribute with qemu  internal varibles.
for example, why the line 61 use "dead:1" and the line 63 use "dead: 0, 1"?  what is the precisely meaning of the number after the "dead:" word?


thank you!     




    60 OP after optimization and liveness analysis:

     61  ld_i32 tmp5,env,$0xffffffffffffffec                 dead: 1

     62  movi_i32 tmp6,$0x0

     63  brcond_i32 tmp5,tmp6,lt,$L0                      dead: 0 1

     64  

     65  ---- 60000004 00000000 00000e04

     66  movi_i32 tmp5,$0x60000010

     67  mov_i32 tmp7,tmp5                                dead: 1

     68  qemu_ld_i32 tmp6,tmp7,leul,3                     dead: 1

     69  mov_i32 r1,tmp6                                  sync: 0  dead: 0 1

     70  goto_tb $0x1

     71  movi_i32 pc,$0x60000008                          sync: 0  dead: 0

     72  exit_tb $0x7f8e8ef58101

     73  set_label $L0

     74  exit_tb $0x7f8e8ef58103

     75  



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Re: What this mean "dead: 1" and "dead: 0 1" on each tb block start?

[Richard Henderson]

On 7/29/20 7:27 AM, tugouxp wrote:
> HI folks:
>   on each tb block start, there are following ir code, and the most confusing
> me is that  the postfix of each line "dead:" flag, what it is represent precisely?
> i guess it may be related to the register or varible liveness for help
> generating tghe target machine code, but i cant get the precisely connection of
> the dead attrribute with qemu  internal varibles.
> for example, why the line 61 use "dead:1" and the line 63 use "dead: 0, 1"? 
> what is the precisely meaning of the number after the "dead:" word?
> 
> thank you!     
> 
> 
>     60 OP after optimization and liveness analysis:
> 
>      61  ld_i32 tmp5,env,$0xffffffffffffffec                 dead: 1
> 
>      62  movi_i32 tmp6,$0x0
> 
>      63  brcond_i32 tmp5,tmp6,lt,$L0                      dead: 0 1

The numbers are the index of the argument that is dead.

E.g. here, both tmp5 and tmp6 are dead.


r~

Re:Re: What this mean "dead: 1" and "dead: 0 1" on each tb block start?

[tugouxp]

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So, flag is also the paramter index right? ,what about the sync ?   

















At 2020-07-30 00:16:25, "Richard Henderson" <richard.henderson@linaro.org> wrote:
>On 7/29/20 7:27 AM, tugouxp wrote:
>> HI folks:
>>   on each tb block start, there are following ir code, and the most confusing
>> me is that  the postfix of each line "dead:" flag, what it is represent precisely?
>> i guess it may be related to the register or varible liveness for help
>> generating tghe target machine code, but i cant get the precisely connection of
>> the dead attrribute with qemu  internal varibles.
>> for example, why the line 61 use "dead:1" and the line 63 use "dead: 0, 1"? 
>> what is the precisely meaning of the number after the "dead:" word?
>> 
>> thank you!     
>> 
>> 
>>     60 OP after optimization and liveness analysis:
>> 
>>      61  ld_i32 tmp5,env,$0xffffffffffffffec                 dead: 1
>> 
>>      62  movi_i32 tmp6,$0x0
>> 
>>      63  brcond_i32 tmp5,tmp6,lt,$L0                      dead: 0 1
>
>The numbers are the index of the argument that is dead.
>
>E.g. here, both tmp5 and tmp6 are dead.
>
>
>r~

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