[PATCH] D31651: Fix in SelectionDAG::getNode() to not produce BUILD_VECTOR operands

[Jonas Paulsson via Phabricator via llvm-commits]

jonpa created this revision.

Continued from: https://bugs.llvm.org//show_bug.cgi?id=32422

About the assert in LegalizeOp() that triggered:

llvm/llvm-dev/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp:921: void {anonymous}::SelectionDAGLegalize::LegalizeOp(llvm::SDNode*): Assertion `(TLI.getTypeAction(*DAG.getContext(), Op.getValueType()) == TargetLowering::TypeLegal || TLI.isTypeLegal(Op.getValueType()) || Op.getOpcode() == ISD::TargetConstant) && "Unexpected illegal type!"' failed.

I wonder why both getTypeAction() and isTypeLegal() are called here - shouldn't they be equivalent?

Follow up question is then If the patch looks reasonable: is it enough with just isTypeLegal()?

I also removed the check
if (Ops.size() == LegalVT.getVectorNumElements())

since it seems redundant with
if (ISD::isBuildVectorOfConstantSDNodes(N1.getNode()))


https://reviews.llvm.org/D31651

Files:
  lib/CodeGen/SelectionDAG/SelectionDAG.cpp


Index: lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4126,35 +4126,36 @@
     assert(EVT.bitsLE(VT) && "Not extending!");
     if (EVT == VT) return N1;  // Not actually extending
 
-    auto SignExtendInReg = [&](APInt Val) {
+    auto SignExtendInReg = [&](APInt Val, llvm::EVT ScalarVT) {
       unsigned FromBits = EVT.getScalarSizeInBits();
       Val <<= Val.getBitWidth() - FromBits;
       Val = Val.ashr(Val.getBitWidth() - FromBits);
-      return getConstant(Val, DL, VT.getScalarType());
+      return getConstant(Val, DL, ScalarVT);
     };
 
     if (N1C) {
       const APInt &Val = N1C->getAPIntValue();
-      return SignExtendInReg(Val);
+      return SignExtendInReg(Val, VT.getScalarType());
     }
     if (ISD::isBuildVectorOfConstantSDNodes(N1.getNode())) {
+      // If the scalar type of VT is not legal, keep the original operand type.
+      llvm::EVT LegalScalarVT = (TLI->isTypeLegal(VT.getScalarType()) ?
+         VT.getScalarType() : N1.getOperand(0).getValueType().getScalarType());
+
       SmallVector<SDValue, 8> Ops;
       for (int i = 0, e = VT.getVectorNumElements(); i != e; ++i) {
         SDValue Op = N1.getOperand(i);
-        if (Op.isUndef()) {
-          Ops.push_back(getUNDEF(VT.getScalarType()));
-          continue;
-        }
-        if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
+        if (Op.isUndef())
+          Ops.push_back(getUNDEF(LegalScalarVT));
+        else {
+          ConstantSDNode *C = cast<ConstantSDNode>(Op);
           APInt Val = C->getAPIntValue();
-          Val = Val.zextOrTrunc(VT.getScalarSizeInBits());
-          Ops.push_back(SignExtendInReg(Val));
+          Val = Val.zextOrTrunc(LegalScalarVT.getSizeInBits());
+          Ops.push_back(SignExtendInReg(Val, LegalScalarVT));
           continue;
         }
-        break;
       }
-      if (Ops.size() == VT.getVectorNumElements())
-        return getBuildVector(VT, DL, Ops);
+      return getBuildVector(VT, DL, Ops);
     }
     break;
   }


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