[llvm] [RegisterCoalescer] Fix crash coalescing COPY from erasable IMPLICIT_DEF (PR #196895)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,88 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=x86_64-unknown-linux-gnu -O3 -o - %s | FileCheck %s
+
+; Regression test for https://github.com/llvm/llvm-project/issues/195587.
+; Register coalescer crashed coalescing a COPY from an erasable IMPLICIT_DEF
+; when a tied-def redef immediately followed. Reduced from C reproducer via
+; llvm-reduce.
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
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arsenm wrote:

```suggestion
```

https://github.com/llvm/llvm-project/pull/196895