[llvm] [SystemZ] Eliminate call sequence instructions early. (PR #77812)

[Ulrich Weigand via llvm-commits]

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@@ -88,13 +88,16 @@ entry:
   ret i64 %retval
 }
 
+; TODO: Unfortunately the lgdr is scheduled below the COPY from $r1d, causing
+; an overlap and thus an extra copy.
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uweigand wrote:

Does the presence of these pseudos help with scheduling around calls in general?  If yes, maybe we can leave them in, and just set the stack size argument always to zero?

https://github.com/llvm/llvm-project/pull/77812