[SelectionDAG] Fix a false assumption that there will always be a valid integer type corresponding to a vector type

`SelectionDAG::getBitcastedAnyExtOrTrunc` assumes that there is always a valid
integer type corresponding to another type, which is not always true when it
comes to vector type. For example, `<3 x i8>` doesn't have a corresponding
integer type.

Fix SWDEV-464698.

Author: shiltian

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -1468,13 +1468,31 @@ SDValue SelectionDAG::getZExtOrTrunc(SDValue Op, const SDLoc &DL, EVT VT) {
 }
 
 SDValue SelectionDAG::getBitcastedAnyExtOrTrunc(SDValue Op, const SDLoc &DL,
-                                                 EVT VT) {
+                                                EVT VT) {
   assert(!VT.isVector());
   auto Type = Op.getValueType();
   SDValue DestOp;
   if (Type == VT)
     return Op;
   auto Size = Op.getValueSizeInBits();
+  auto IntTy = MVT::getIntegerVT(Size);
+
+  if (!IntTy.isValid()) {
+    // We assume integers of "weird" size have already been legalized here.
+    assert(Type.isVector());
+    unsigned NumElements = Type.getVectorNumElements();
+    unsigned ExtSize = VT.getScalarSizeInBits();
+    EVT ElementType = Type.getVectorElementType();
+    unsigned ExtNumElements = ExtSize / ElementType.getScalarSizeInBits();
+    assert(NumElements < ExtNumElements);
+    MVT ExtType = MVT::getVectorVT(ElementType.getSimpleVT(), ExtNumElements);
+    SmallVector<SDValue, 4> Ops(ExtNumElements, getUNDEF(ElementType));
+    SDValue ExtVec = getNode(ISD::BUILD_VECTOR, DL, ExtType, Ops);
+    DestOp = getNode(ISD::INSERT_SUBVECTOR, DL, ExtType, ExtVec, Op,
+                     getVectorIdxConstant(0, DL));
+    return getBitcast(VT, DestOp);
+  }
+
   DestOp = getBitcast(MVT::getIntegerVT(Size), Op);
   if (DestOp.getValueType() == VT)
     return DestOp;

llvm/test/CodeGen/AMDGPU/no-corresponding-integer-type.ll

@@ -0,0 +1,13 @@
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx942 %s -o -
+
+define void @no_corresponding_integer_type(i8 %arg, ptr addrspace(1) %ptr) {
+entry:
+  %load = load <3 x i8>, ptr addrspace(1) %ptr, align 1
+  %elt0 = extractelement <3 x i8> %load, i64 0
+  %mul0 = mul i8 %elt0, %arg
+  %or = or i8 %mul0, 1
+  %mul1 = mul i8 %arg, %arg
+  %add = add i8 %mul1, %or
+  store i8 %add, ptr addrspace(1) %ptr, align 1
+  ret void
+}