[llvm] [AMDGPU] misched: avoid subregister dependencies (PR #140255)

[Matt Arsenault via llvm-commits]

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@@ -656,6 +764,13 @@ void GCNSubtarget::adjustSchedDependency(
   MachineInstr *DefI = Def->getInstr();
   MachineInstr *UseI = Use->getInstr();
 
+  if (Register Reg = getRealSchedDependency(*DefI, DefOpIdx, *UseI, UseOpIdx)) {
+    Dep.setReg(Reg);
+  } else {
+    Dep = SDep(Def, SDep::Artificial);
+    return; // this is not a data dependency anymore
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arsenm wrote:

```suggestion
    return; // This is not a data dependency anymore.
```

https://github.com/llvm/llvm-project/pull/140255