[llvm] [CodeGen][RegCoalescer] Shrink non-PHI live-through subranges (PR #216297)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,35 @@
+# RUN: llc -mtriple=aarch64 \
+# RUN:   -aarch64-enable-subreg-liveness-tracking \
+# RUN:   -run-pass=register-coalescer -debug-only=regalloc \
+# RUN:   -o /dev/null %s 2>&1 | FileCheck %s
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arsenm wrote:

```suggestion
# RUN:   -filetype=null %s 2>&1 | FileCheck %s
```

https://github.com/llvm/llvm-project/pull/216297