[llvm] [SPARC] Emit a TRUNCATE when combining truncating BSWAP-STOREs (PR #210483)

[via llvm-commits]

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@@ -3333,6 +3333,9 @@ SDValue SparcTargetLowering::PerformSTORECombine(SDNode *N,
       unsigned Shift = VT.getSizeInBits() - MemVT.getSizeInBits();
       BSwapOp = DAG.getNode(ISD::SRL, DL, VT, BSwapOp,
                             DAG.getShiftAmountConstant(Shift, VT, DL));
+      // Need to truncate if this is a bswap of i64 stored as i32/i16.
+      if (VT == MVT::i64)
+        BSwapOp = DAG.getNode(ISD::TRUNCATE, DL, MVT::i32, BSwapOp);
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koachan wrote:

> > I'm thinking that the extra patterns would match the already defined i32->i16 one...
>
> I'm not sure I undersnant what you're trying to say?..

Was just thinking that I already defined i32->i16 patterns anyway so defining additional patterns for i64->i32 and i64->i16 will be cleaner than special casing it through TRUNCATEs.

https://github.com/llvm/llvm-project/pull/210483