[llvm] [AMDGPU][MIR] Serialize SpillPhysVGPRs (PR #113129)

[Matt Arsenault via llvm-commits]

================
@@ -0,0 +1,57 @@
+# RUN: llc -mtriple=amdgcn-amd-amdhsa --start-before=si-lower-sgpr-spills --stop-after=prologepilog -o - %s | FileCheck %s
+
+# CHECK: csr_sgpr_spill
+# CHECK: spillPhysVGPRs:
+# CHECK-NEXT: - '$vgpr0'
+---
+name: csr_sgpr_spill
+tracksRegLiveness: true
+body: |
+  bb.0:
+    S_NOP 0
+  bb.1:
+    $sgpr40 = S_MOV_B32 0
+    $sgpr41 = S_MOV_B32 1
+
+...
+
+# CHECK-LABEL: name: parse_none
+# CHECK: machineFunctionInfo:
+# CHECK-NOT: spillPhysVGPRs:
----------------
arsenm wrote:

```suggestion
# CHECK-NOT: spillPhysVGPRs
```

-NEXT checks would be more reliable 

https://github.com/llvm/llvm-project/pull/113129