[llvm] [RISCV][backend] port `(not (add X, -1)) -> (neg X)` to GlobalISel (PR #181640)

[Luisa Cicolini via llvm-commits]

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@@ -2120,7 +2120,7 @@ class LLVM_ABI MachineIRBuilder {
                                 std::optional<unsigned> Flags = std::nullopt) {
     return buildInstr(TargetOpcode::G_FNEG, {Dst}, {Src0}, Flags);
   }
-
+  
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luisacicolini wrote:

```suggestion
```

https://github.com/llvm/llvm-project/pull/181640