| Issue |
52907
|
| Summary |
[amdgpu] compiling for gfx9 spills a LOT into 64 vgpr
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
raikonenfnu
|
Hey guys, I am trying to compile some llvmir for gfx908, it seems like it have a lot of spiils but is only trying to fit in 64 vgpr, which is weird since IIRC it should have 256 vgpr.
Here is the llvmir I use to compile: [ll file](https://gist.github.com/raikonenfnu/763bf67d0f9f8d3833fd3f3978bb2d8e)
Compiling with llc-13 will generate an [assembly file](https://gist.github.com/raikonenfnu/763bf67d0f9f8d3833fd3f3978bb2d8e#file-output__inference_learn_29220_dispatch_227-s-L5325-L5336) where we can see that it has 654 vgpr spill with 64 vgpr count.
```bash
/usr/bin/llc-13 -mtriple=amdgcn--amdhsa-amdgiz --march=amdgcn -mcpu=gfx908 /home/stanley/output__inference_learn_29220_dispatch_227.ll -filetype=asm
# output assembly file seen [here](https://gist.github.com/raikonenfnu/763bf67d0f9f8d3833fd3f3978bb2d8e#file-output__inference_learn_29220_dispatch_227-s-L5325-L5336)
```
I have also tried compiling with llc generated from [llvm-project linked in aomp](https://github.com/RadeonOpenCompute/llvm-project/tree/amd-stg-open/llvm), which would present a detailed error of:
```bash
./llc -mtriple=amdgcn--amdhsa-amdgiz --march=amdgcn -mcpu=gfx908 /home/stanley/output__inference_learn_29220_dispatch_227.ll -filetype=asm
LLVM ERROR: Error while trying to spill VGPR0 from class VGPR_32: Cannot scavenge register without an emergency spill slot!
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0. Program arguments: ./llc -mtriple=amdgcn--amdhsa-amdgiz --march=amdgcn -mcpu=gfx908 /home/stanley/output__inference_learn_29220_dispatch_227.ll -filetype=asm
1. Running pass 'CallGraph Pass Manager' on module '/home/stanley/output__inference_learn_29220_dispatch_227.ll'.
2. Running pass 'Prologue/Epilogue Insertion & Frame Finalization' on function '@__inference_learn_29220_dispatch_227'
```
Could there be some bug in the spill/register allocation code for AMDGPU backend?
Any advice/comments/guidance would be very helpful!
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