[LLVM][SelectionDAG] Ensure Constant[FP]SDnode only store references to scalar Constant{Int,FP}.

This fixes a failure path when the use-constant-##-for-###-splat
IR options are enabled.

Author: paulwalker-arm

llvm/include/llvm/CodeGen/SelectionDAGNodes.h

@@ -1678,6 +1678,7 @@ class ConstantSDNode : public SDNode {
       : SDNode(isTarget ? ISD::TargetConstant : ISD::Constant, 0, DebugLoc(),
                VTs),
         Value(val) {
+    assert(!isa<VectorType>(val->getType()) && "Unexpected vector type!");
     ConstantSDNodeBits.IsOpaque = isOpaque;
   }
 
@@ -1730,7 +1731,9 @@ class ConstantFPSDNode : public SDNode {
   ConstantFPSDNode(bool isTarget, const ConstantFP *val, SDVTList VTs)
       : SDNode(isTarget ? ISD::TargetConstantFP : ISD::ConstantFP, 0,
                DebugLoc(), VTs),
-        Value(val) {}
+        Value(val) {
+    assert(!isa<VectorType>(val->getType()) && "Unexpected vector type!");
+  }
 
 public:
   const APFloat& getValueAPF() const { return Value->getValueAPF(); }

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -1656,6 +1656,11 @@ SDValue SelectionDAG::getConstant(const ConstantInt &Val, const SDLoc &DL,
   EVT EltVT = VT.getScalarType();
   const ConstantInt *Elt = &Val;
 
+  // Vector splats are explicit within the DAG, with ConstantSDNode holding the
+  // to be splatted scalar ConstantInt.
+  if (isa<VectorType>(Elt->getType()))
+    Elt = ConstantInt::get(*getContext(), Elt->getValue());
+
   // In some cases the vector type is legal but the element type is illegal and
   // needs to be promoted, for example v8i8 on ARM.  In this case, promote the
   // inserted value (the type does not need to match the vector element type).
@@ -1809,6 +1814,12 @@ SDValue SelectionDAG::getConstantFP(const ConstantFP &V, const SDLoc &DL,
   assert(VT.isFloatingPoint() && "Cannot create integer FP constant!");
 
   EVT EltVT = VT.getScalarType();
+  const ConstantFP *Elt = &V;
+
+  // Vector splats are explicit within the DAG, with ConstantFPSDNode holding
+  // the to be splatted scalar ConstantFP.
+  if (isa<VectorType>(Elt->getType()))
+    Elt = ConstantFP::get(*getContext(), Elt->getValue());
 
   // Do the map lookup using the actual bit pattern for the floating point
   // value, so that we don't have problems with 0.0 comparing equal to -0.0, and
@@ -1817,15 +1828,15 @@ SDValue SelectionDAG::getConstantFP(const ConstantFP &V, const SDLoc &DL,
   SDVTList VTs = getVTList(EltVT);
   FoldingSetNodeID ID;
   AddNodeIDNode(ID, Opc, VTs, {});
-  ID.AddPointer(&V);
+  ID.AddPointer(Elt);
   void *IP = nullptr;
   SDNode *N = nullptr;
   if ((N = FindNodeOrInsertPos(ID, DL, IP)))
     if (!VT.isVector())
       return SDValue(N, 0);
 
   if (!N) {
-    N = newSDNode<ConstantFPSDNode>(isTarget, &V, VTs);
+    N = newSDNode<ConstantFPSDNode>(isTarget, Elt, VTs);
     CSEMap.InsertNode(N, IP);
     InsertNode(N);
   }

llvm/test/CodeGen/AArch64/sve-fp-immediates-merging.ll

@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc < %s | FileCheck %s
+; RUN: llc -use-constant-fp-for-scalable-splat < %s | FileCheck %s
 
 target triple = "aarch64-unknown-linux-gnu"
 

llvm/test/CodeGen/AArch64/sve-int-imm.ll

@@ -1,4 +1,5 @@
 ; RUN: llc -mtriple=aarch64-linux-gnu -mattr=+sve < %s | FileCheck %s
+; RUN: llc -mtriple=aarch64-linux-gnu -mattr=+sve -use-constant-int-for-scalable-splat < %s | FileCheck %s
 
 ;
 ; SVE Arith Vector Immediate Unpredicated CodeGen