[llvm] [LoongArch] Custom lowering for 128-bit vector integer shifts (PR #171097)

[Lu Weining via llvm-commits]

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@@ -618,10 +618,71 @@ SDValue LoongArchTargetLowering::LowerOperation(SDValue Op,
     return lowerVECREDUCE(Op, DAG);
   case ISD::ConstantFP:
     return lowerConstantFP(Op, DAG);
+  case ISD::SRA:
+  case ISD::SRL:
+  case ISD::SHL:
+    return lowerVectorSRA_SRL_SHL(Op, DAG);
   }
   return SDValue();
 }
 
+/// getVShiftImm - Check if this is a valid build_vector for the immediate
+/// operand of a vector shift operation, where all the elements of the
+/// build_vector must have the same constant integer value.
+static bool getVShiftImm(SDValue Op, unsigned ElementBits, int64_t &Cnt) {
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SixWeining wrote:

Generally, `amt` is used to represent the shift amount.

```suggestion
static bool getVShiftAmt(SDValue Op, unsigned ElementBits, int64_t &Amt) {
```

https://github.com/llvm/llvm-project/pull/171097