[llvm] [MachinePipeliner] Remove UB from tests (NFC) (PR #123169)

[Ryotaro Kasuga via llvm-commits]

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@@ -20,9 +20,9 @@ for.body.prol:
   %sr.prol = phi float [ %0, %for.body.prol ], [ undef, %entry ]
   %sr109.prol = phi float [ %sr.prol, %for.body.prol ], [ undef, %entry ]
   %prol.iter = phi i32 [ %prol.iter.sub, %for.body.prol ], [ undef, %entry ]
-  %0 = load float, ptr undef, align 4
+  %0 = load float, ptr %p0, align 4
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kasuga-fj wrote:

Using undef/null as a pointer operand for load/store causes UB.
https://llvm.org/docs/LangRef.html#undefined-values

https://github.com/llvm/llvm-project/pull/123169