[llvm] [AArch64][GlobalISel] Reland Make G_DUP immediate 32-bits or larger (#96780) (PR #99014)

[Amara Emerson via llvm-commits]

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@@ -792,8 +813,13 @@ AArch64RegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
              (getRegBank(ScalarReg, MRI, TRI) == &AArch64::FPRRegBank ||
               onlyDefinesFP(*ScalarDef, MRI, TRI)))
       OpRegBankIdx = {PMI_FirstFPR, PMI_FirstFPR};
-    else
+    else {
+      if (ScalarTy.getSizeInBits() < 32 &&
+          getRegBank(ScalarReg, MRI, TRI) == &AArch64::GPRRegBank)
+        // Calls applyMappingImpl()
+        MappingID = CustomMappingID;
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aemerson wrote:

You should wrap this in a brace if you want a comment on a line. Otherwise you can  append the comment to the end of the `MappingID = CustomMappingID;` line.

https://github.com/llvm/llvm-project/pull/99014