[llvm] Allow MIN/MAX signedness flip when operands are known-negative (PR #174469)

[via llvm-commits]

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@@ -0,0 +1,52 @@
+; RUN: llc -mtriple=x86_64-unknown-unknown -mattr=+sse2,-sse4.1 < %s | FileCheck %s
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fbrv wrote:

@RKSimon I'm not sure about the regression test, is the first time I'm writing something like this. I read lot of other tests and most of them has the comment
```
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
```
But I'm not sure this can be applied to this pr

https://github.com/llvm/llvm-project/pull/174469