[llvm] [SLP] Move some of X86 tests to common directory (PR #106401)

[Florian Hahn via llvm-commits]

================
@@ -1,5 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; REQUIRES: target={{aarch64|x86_64}}-{{.*}}
----------------
fhahn wrote:

Did you check this works as expected?

With this patch merged, those tests are now considered 'unsupported' even when all targets are enabled.

You can check this by applying the patch below and observe that there are no test failures

```
diff --git a/llvm/test/Transforms/SLPVectorizer/alternate-cmp-swapped-pred-parent.ll b/llvm/test/Transforms/SLPVectorizer/alternate-cmp-swapped-pred-parent.ll
index a709af4cf858..1511dfbe37b6 100644
--- a/llvm/test/Transforms/SLPVectorizer/alternate-cmp-swapped-pred-parent.ll
+++ b/llvm/test/Transforms/SLPVectorizer/alternate-cmp-swapped-pred-parent.ll
@@ -6,7 +6,6 @@
 define void @test() {
 ; CHECK-LABEL: @test(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[CALL37:%.*]] = load i16, ptr poison, align 2
 ; CHECK-NEXT:    br label [[BB:%.*]]
 ; CHECK:       bb:
 ; CHECK-NEXT:    [[CALL:%.*]] = load i16, ptr poison, align 2
```

https://github.com/llvm/llvm-project/pull/106401