[llvm] [RISCV] Add patterns for fixed vector vwsll (PR #87316)

[Craig Topper via llvm-commits]

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@@ -3287,24 +3287,25 @@ bool RISCVDAGToDAGISel::selectVSplatUimm(SDValue N, unsigned Bits,
 }
 
 bool RISCVDAGToDAGISel::selectLow8BitsVSplat(SDValue N, SDValue &SplatVal) {
-  // Truncates are custom lowered during legalization.
-  auto IsTrunc = [this](SDValue N) {
-    if (N->getOpcode() != RISCVISD::TRUNCATE_VECTOR_VL)
+  auto IsExtOrTrunc = [](SDValue N) {
+    switch (N->getOpcode()) {
+    case ISD::SIGN_EXTEND:
+    case ISD::ZERO_EXTEND:
+    // There's no passthru on these _VL nodes so any VL/mask is ok, since any
+    // inactive elements will be undef.
+    case RISCVISD::TRUNCATE_VECTOR_VL:
+    case RISCVISD::VSEXT_VL:
+    case RISCVISD::VZEXT_VL:
+      return true;
+    default:
       return false;
-    SDValue VL;
-    selectVLOp(N->getOperand(2), VL);
-    // Any vmset_vl is ok, since any bits past VL are undefined and we can
-    // assume they are set.
-    return N->getOperand(1).getOpcode() == RISCVISD::VMSET_VL &&
-           isa<ConstantSDNode>(VL) &&
-           cast<ConstantSDNode>(VL)->getSExtValue() == RISCV::VLMaxSentinel;
+    }
+    return true;
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topperc wrote:

This retun is unreachable

https://github.com/llvm/llvm-project/pull/87316