[llvm] [AMDGPU][LIT] Added a MIR LIT showing the SGPR spills (PR #94584)

[Christudasan Devadasan via llvm-commits]

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+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx908 -verify-machineinstrs -stress-regalloc=3 -start-before=greedy,0 -stop-after=si-lower-sgpr-spills -o - %s | FileCheck -check-prefix=SGPR_SPILLED %s
+
+# INFO : The pass pipeline is started from before the first iteration of register allocation pass that represents SGPR allocation in AMDGPU pipleine.
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cdevadas wrote:

```suggestion
# INFO : The test starts from the sgpr-regalloc pipeline.
```

https://github.com/llvm/llvm-project/pull/94584