[llvm] [Xtensa] Implement base CallConvention. (PR #83280)

[Sergei Barannikov via llvm-commits]

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@@ -23,5 +24,139 @@
 
 using namespace llvm;
 
+static inline const MachineInstrBuilder &
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s-barannikov wrote:

```suggestion
static const MachineInstrBuilder &
```

https://github.com/llvm/llvm-project/pull/83280