[llvm] [AArch64][GlobalISel] Avoid cross bank copies for NEON vcvtfp2fx results (PR #213277)

[Kieran B via llvm-commits]

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@@ -1442,6 +1440,32 @@ AArch64RegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
       // OpRegBankIdx[1] is the intrinsic ID.
       // OpRegBankIdx[3] is an integer immediate.
       break;
+    case Intrinsic::aarch64_neon_vcvtfp2fxs:
+    case Intrinsic::aarch64_neon_vcvtfp2fxu: {
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kieroxide wrote:

This case duplicates most of the logic from the previous case on line 1409.  The only differences are checking the srcSize instead of dstSize and not checking hasFPRCVT as fp2fx has no FPRCVT instruction variants. 

If requested, I can create a helper to reduce the duplication for these two case blocks 

https://github.com/llvm/llvm-project/pull/213277