[llvm] [RISCV] Create disjoint or in RISCVGatherScatterLowering (PR #151981)

[Min-Yih Hsu via llvm-commits]

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@@ -167,9 +167,8 @@ static std::pair<Value *, Value *> matchStridedStart(Value *Start,
   default:
     llvm_unreachable("Unexpected opcode");
   case Instruction::Or:
-    // TODO: We'd be better off creating disjoint or here, but we don't yet
-    // have an IRBuilder API for that.
-    [[fallthrough]];
+    Start = Builder.CreateOr(Start, Splat, "", /* IsDisjoint = */ true);
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mshockwave wrote:

```suggestion
    Start = Builder.CreateOr(Start, Splat, "", /*IsDisjoint=*/true);
```

https://github.com/llvm/llvm-project/pull/151981