[LegalizeTypes] When promoting BITREVERSE/BSWAP don't take the shift amount into account when determining the shift amount VT.

If the target's preferred shift amount VT can't hold any shift
amount for the promoted VT, we should use i32. The specific shift
amount shouldn't matter. The type will be adjusted later when the
shift itself is type legalized. This avoids an assert in getNode.

Fixes PR43820.

Author: topperc

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

@@ -365,15 +365,15 @@ SDValue DAGTypeLegalizer::PromoteIntRes_BITCAST(SDNode *N) {
                      CreateStackStoreLoad(InOp, OutVT));
 }
 
-// Helper for BSWAP/BITREVERSE promotion to ensure we can fit the shift amount
+// Helper for BSWAP/BITREVERSE promotion to ensure we can fit any shift amount
 // in the VT returned by getShiftAmountTy and to return a safe VT if we can't.
-static EVT getShiftAmountTyForConstant(unsigned Val, EVT VT,
-                                       const TargetLowering &TLI,
+static EVT getShiftAmountTyForConstant(EVT VT, const TargetLowering &TLI,
                                        SelectionDAG &DAG) {
   EVT ShiftVT = TLI.getShiftAmountTy(VT, DAG.getDataLayout());
-  // If the value won't fit in the prefered type, just use something safe. It
-  // will be legalized when the shift is expanded.
-  if ((Log2_32(Val) + 1) > ShiftVT.getScalarSizeInBits())
+  // If any possible shift value won't fit in the prefered type, just use
+  // something safe. It will be legalized when the shift is expanded.
+  if (!ShiftVT.isVector() &&
+      ShiftVT.getSizeInBits() < Log2_32_Ceil(VT.getSizeInBits()))
     ShiftVT = MVT::i32;
   return ShiftVT;
 }
@@ -385,7 +385,7 @@ SDValue DAGTypeLegalizer::PromoteIntRes_BSWAP(SDNode *N) {
   SDLoc dl(N);
 
   unsigned DiffBits = NVT.getScalarSizeInBits() - OVT.getScalarSizeInBits();
-  EVT ShiftVT = getShiftAmountTyForConstant(DiffBits, NVT, TLI, DAG);
+  EVT ShiftVT = getShiftAmountTyForConstant(NVT, TLI, DAG);
   return DAG.getNode(ISD::SRL, dl, NVT, DAG.getNode(ISD::BSWAP, dl, NVT, Op),
                      DAG.getConstant(DiffBits, dl, ShiftVT));
 }
@@ -397,7 +397,7 @@ SDValue DAGTypeLegalizer::PromoteIntRes_BITREVERSE(SDNode *N) {
   SDLoc dl(N);
 
   unsigned DiffBits = NVT.getScalarSizeInBits() - OVT.getScalarSizeInBits();
-  EVT ShiftVT = getShiftAmountTyForConstant(DiffBits, NVT, TLI, DAG);
+  EVT ShiftVT = getShiftAmountTyForConstant(NVT, TLI, DAG);
   return DAG.getNode(ISD::SRL, dl, NVT,
                      DAG.getNode(ISD::BITREVERSE, dl, NVT, Op),
                      DAG.getConstant(DiffBits, dl, ShiftVT));
@@ -1058,8 +1058,7 @@ SDValue DAGTypeLegalizer::PromoteIntRes_XMULO(SDNode *N, unsigned ResNo) {
   if (N->getOpcode() == ISD::UMULO) {
     // Unsigned overflow occurred if the high part is non-zero.
     unsigned Shift = SmallVT.getScalarSizeInBits();
-    EVT ShiftTy = getShiftAmountTyForConstant(Shift, Mul.getValueType(),
-                                              TLI, DAG);
+    EVT ShiftTy = getShiftAmountTyForConstant(Mul.getValueType(), TLI, DAG);
     SDValue Hi = DAG.getNode(ISD::SRL, DL, Mul.getValueType(), Mul,
                              DAG.getConstant(Shift, DL, ShiftTy));
     Overflow = DAG.getSetCC(DL, N->getValueType(1), Hi,