[llvm-dev] register spilling and printing live variables

[Dangeti Tharun kumar via llvm-dev]

Hi

On Fri, Oct 25, 2019 at 11:40 AM Priyanka Panigrahi via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hello,
>
> I have studied register allocation in theoretical aspects and exploring
> the same in the implementation level.
>
> I need a minimal testcase for register spilling to analyze spilling
> procedure in llvm. I tried with a testcase taking 20 variables but all the
> 20 variables are getting stored in the stack using %rbp. Maybe my live
> variable analysis is wrong. Please help me with a minimal testcase to
> explore register spilling in llvm,
>

You can share your testcase, people can have a look at it

>
> Is there any way to print the maximum live variables in source code. So
> that we can find out the minimum registers required for execution. Also, is
> it possible to print the register map of each variable in source code.
>

*-debug-only=regalloc *will dump a lot of information including live
intervals and register maps.
Something like this.

********** REWRITE VIRTUAL REGISTERS **********
********** Function: main
********** REGISTER MAP **********
[%0 -> $r12] GR64_with_sub_8bit
[%1 -> $r15] GR64_with_sub_8bit
[%9 -> $rsi] GR64_with_sub_8bit
[%10 -> $rdx] GR64_with_sub_8bit
[%14 -> $xmm1] FR32
[%17 -> $xmm1] FR32
[%20 -> $xmm1] FR32
[%27 -> $r15] GR64
[%35 -> $rdi] GR64
[%38 -> $xmm0] FR64
[%39 -> $xmm0] FR32
[%44 -> $xmm0] FR32
[%45 -> $xmm0] FR64
[%56 -> $rcx] GR64_with_sub_8bit
[%60 -> $rdi] GR64_with_sub_8bit
[%66 -> $rax] GR64_with_sub_8bit
[%73 -> $xmm0] FR32
[%74 -> $xmm0] FR64
[%82 -> $rbx] GR64_NOSP
[%83 -> $rbx] GR64_NOSP
[%87 -> $rdi] GR64_NOSP
[%88 -> $xmm0] FR32
[%90 -> $rbx] GR64_NOSP
[%91 -> $rbx] GR64_NOSP
[%93 -> $r14] GR64_with_sub_8bit



>
> Any help would be appreciated.
> Thank you in advance.
>
> Regards,
> Priyanka
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> llvm-dev at lists.llvm.org
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>


-- 
Regards,
DTharun
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