Add support for STRICT_FSETCC promotion

[thopre]

Summary

Add missing handling of STRICT_FSETCC promotion. This prevents assert
failure in llvm::TargetLoweringBase::getTypeToPromoteTo().

[uweigand]

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

4618

When expanding a strict FP operation, we need to take care to never emit any non-strict operation. It looks like the patch as currently written might cause a "FP_EXTEND" to be emitted, which would violate that rule.

We need to emit a STRICT_FP_EXTEND instead (which needs to be properly chained just before the new STRICT_FSETCC node). Then everything should be OK since the only case where STRICT_FP_EXTEND might raise an exception is if the input is a (signaling) NaN, in which case the original STRICT_FSETCC would also have raised an exception.

[uweigand]

Oh, any another thing: we might also want to handle STRICT_FSETCCS in addition to STRICT_FSETCC.

[thopre]

Use STRICT_FP_EXTEND for strict FP and also add support for STRICT_FSETCCS

[uweigand]

See the two inline comments about STRICT_FSETCCS. I guess that shows this path is not really exercised right now -- maybe it would be a good idea to add some tests.

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

4421

I guess this needs to handle STRICT_FSETCCS here as well.

4632

Should use STRICT_FSETCCS here if we're expanding STRICT_FSETCCS.

[thopre]

In D91962#2413568, @uweigand wrote:

See the two inline comments about STRICT_FSETCCS. I guess that shows this path is not really exercised right now -- maybe it would be a good idea to add some tests.

The problem is that no target currently promote a STRICT_FSETCC or STRICT_FSETCCS. Our target does which is how I found out the assert failure but I haven't implemented STRICT_FSETCCS yet.

[uweigand]

OK, I see. I guess the patch LGTM then with the two issues fixed.

[thopre]

Fix promotion for STRICT_FSETCCS

[uweigand]

LGTM, thanks!

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

void SelectionDAGLegalize::PromoteNode(SDNode *Node) {
   if (Node->getOpcode() == ISD::UINT_TO_FP ||
       Node->getOpcode() == ISD::SINT_TO_FP ||
       Node->getOpcode() == ISD::SETCC ||
       Node->getOpcode() == ISD::EXTRACT_VECTOR_ELT ||
       Node->getOpcode() == ISD::INSERT_VECTOR_ELT) {
     OVT = Node->getOperand(0).getSimpleValueType();
   }
   if (Node->getOpcode() == ISD::STRICT_UINT_TO_FP ||
-      Node->getOpcode() == ISD::STRICT_SINT_TO_FP)
+      Node->getOpcode() == ISD::STRICT_SINT_TO_FP ||
+      Node->getOpcode() == ISD::STRICT_FSETCC)
     OVT = Node->getOperand(1).getSimpleValueType();
   if (Node->getOpcode() == ISD::BR_CC)
     OVT = Node->getOperand(2).getSimpleValueType();
   MVT NVT = TLI.getTypeToPromoteTo(Node->getOpcode(), OVT);
   SDLoc dl(Node);
   SDValue Tmp1, Tmp2, Tmp3;
   switch (Node->getOpcode()) {
   case ISD::CTTZ:
case ISD::VECTOR_SHUFFLE: {
     Tmp2 = DAG.getNode(ISD::BITCAST, dl, NVT, Node->getOperand(1));
 
     // Convert the shuffle mask to the right # elements.
     Tmp1 = ShuffleWithNarrowerEltType(NVT, OVT, dl, Tmp1, Tmp2, Mask);
     Tmp1 = DAG.getNode(ISD::BITCAST, dl, OVT, Tmp1);
     Results.push_back(Tmp1);
     break;
   }
-  case ISD::SETCC: {
+  case ISD::SETCC:
+  case ISD::STRICT_FSETCC:
+  case ISD::STRICT_FSETCCS: {
     unsigned ExtOp = ISD::FP_EXTEND;
     if (NVT.isInteger()) {
-      ISD::CondCode CCCode =
-        cast<CondCodeSDNode>(Node->getOperand(2))->get();
+      ISD::CondCode CCCode = cast<CondCodeSDNode>(Node->getOperand(2))->get();
       ExtOp = isSignedIntSetCC(CCCode) ? ISD::SIGN_EXTEND : ISD::ZERO_EXTEND;
     }
+    if (Node->isStrictFPOpcode()) {
+      SDValue InChain = Node->getOperand(0);
+      std::tie(Tmp1, std::ignore) =
+          DAG.getStrictFPExtendOrRound(Node->getOperand(1), InChain, dl, NVT);
+      std::tie(Tmp2, std::ignore) =
+          DAG.getStrictFPExtendOrRound(Node->getOperand(2), InChain, dl, NVT);
+      SmallVector<SDValue, 2> TmpChains = {Tmp1.getValue(1), Tmp2.getValue(1)};
+      SDValue OutChain = DAG.getTokenFactor(dl, TmpChains);
+      SDVTList VTs = DAG.getVTList(Node->getValueType(0), MVT::Other);
+      Results.push_back(DAG.getNode(ISD::STRICT_FSETCC, dl, VTs,
+                                    {OutChain, Tmp1, Tmp2, Node->getOperand(3)},
+                                    Node->getFlags()));
+      Results.push_back(Results.back().getValue(1));
+      break;
+    }
     Tmp1 = DAG.getNode(ExtOp, dl, NVT, Node->getOperand(0));
     Tmp2 = DAG.getNode(ExtOp, dl, NVT, Node->getOperand(1));
     Results.push_back(DAG.getNode(ISD::SETCC, dl, Node->getValueType(0), Tmp1,
                                   Tmp2, Node->getOperand(2), Node->getFlags()));
     break;
   }
   case ISD::BR_CC: {
     unsigned ExtOp = ISD::FP_EXTEND;