[llvm] [AMDGPU][SIInsertWaitcnts] Fix iota_range assertion when OtherMarks is empty in mergeAsyncMarks() (PR #193499)

[Shilei Tian via llvm-commits]

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@@ -0,0 +1,139 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 6
+# RUN: llc -mtriple=amdgcn -mcpu=gfx1250 -run-pass=si-insert-waitcnts -o - %s | FileCheck %s
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shiltian wrote:

```suggestion
# RUN: llc -mtriple=amdgcn -mcpu=gfx1250 -run-pass=si-insert-waitcnts < %s | FileCheck %s
```

https://github.com/llvm/llvm-project/pull/193499