[llvm] [AArch64] merge index address with large offset into base address (PR #72187)

[David Green via llvm-commits]

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@@ -1069,6 +1069,42 @@ bool AArch64DAGToDAGISel::SelectAddrModeIndexedBitWidth(SDValue N, bool IsSigned
   return true;
 }
 
+// 16-bit optionally shifted immediates are legal for single mov.
+static bool isLegalSingleMOVImmediate(int64_t Immed) {
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davemgreen wrote:

Can this make use of expandMOVImm?
```
    AArch64_IMM::expandMOVImm(UImm, BitSize, Insn);
    if (Insn.size() != 1)
      return;
```

https://github.com/llvm/llvm-project/pull/72187