[llvm] Use umin for x != 0 when +cssc is enabled (PR #169159)

[Benjamin Maxwell via llvm-commits]

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@@ -0,0 +1,82 @@
+; RUN: llc -mtriple=aarch64-- -o - < %s | FileCheck %s --check-prefixes=CHECK,CHECK-SD
+; RUN: llc -mtriple=aarch64-- -mattr=+cssc -o - < %s | FileCheck %s --check-prefixes=CHECK,CHECK-CSSC
----------------
MacDue wrote:

Remove the common check, since these are never expected to match. That should remove the "These prefixes are unused" note at the bottom. 
```suggestion
; RUN: llc -mtriple=aarch64-- -o - < %s | FileCheck %s --check-prefix=CHECK
; RUN: llc -mtriple=aarch64-- -mattr=+cssc -o - < %s | FileCheck %s --check-prefix=CHECK-CSSC
```

https://github.com/llvm/llvm-project/pull/169159