[VP][RISCV] Add a vp.load.ff intrinsic for fault only first load. (#128593)

There's been some interest in supporting early-exit loops recently.
https://discourse.llvm.org/t/rfc-supporting-more-early-exit-loops/84690

This patch was extracted from our downstream where we've been using it
in our vectorizer.

1 files changed, 36 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 61f1144..71a175d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -837,6 +837,14 @@ static void AddNodeIDCustom(FoldingSetNodeID &ID, const SDNode *N) {
     ID.AddInteger(ELD->getMemOperand()->getFlags());
     break;
   }
+  case ISD::VP_LOAD_FF: {
+    const auto *LD = cast<VPLoadFFSDNode>(N);
+    ID.AddInteger(LD->getMemoryVT().getRawBits());
+    ID.AddInteger(LD->getRawSubclassData());
+    ID.AddInteger(LD->getPointerInfo().getAddrSpace());
+    ID.AddInteger(LD->getMemOperand()->getFlags());
+    break;
+  }
   case ISD::VP_STORE: {
     const VPStoreSDNode *EST = cast<VPStoreSDNode>(N);
     ID.AddInteger(EST->getMemoryVT().getRawBits());
@@ -10433,6 +10441,34 @@ SDValue SelectionDAG::getMaskedHistogram(SDVTList VTs, EVT MemVT,
   return V;
 }
 
+SDValue SelectionDAG::getLoadFFVP(EVT VT, const SDLoc &DL, SDValue Chain,
+                                  SDValue Ptr, SDValue Mask, SDValue EVL,
+                                  MachineMemOperand *MMO) {
+  SDVTList VTs = getVTList(VT, EVL.getValueType(), MVT::Other);
+  SDValue Ops[] = {Chain, Ptr, Mask, EVL};
+  FoldingSetNodeID ID;
+  AddNodeIDNode(ID, ISD::VP_LOAD_FF, VTs, Ops);
+  ID.AddInteger(VT.getRawBits());
+  ID.AddInteger(getSyntheticNodeSubclassData<VPLoadFFSDNode>(DL.getIROrder(),
+                                                             VTs, VT, MMO));
+  ID.AddInteger(MMO->getPointerInfo().getAddrSpace());
+  ID.AddInteger(MMO->getFlags());
+  void *IP = nullptr;
+  if (SDNode *E = FindNodeOrInsertPos(ID, DL, IP)) {
+    cast<VPLoadFFSDNode>(E)->refineAlignment(MMO);
+    return SDValue(E, 0);
+  }
+  auto *N = newSDNode<VPLoadFFSDNode>(DL.getIROrder(), DL.getDebugLoc(), VTs,
+                                      VT, MMO);
+  createOperands(N, Ops);
+
+  CSEMap.InsertNode(N, IP);
+  InsertNode(N);
+  SDValue V(N, 0);
+  NewSDValueDbgMsg(V, "Creating new node: ", this);
+  return V;
+}
+
 SDValue SelectionDAG::getGetFPEnv(SDValue Chain, const SDLoc &dl, SDValue Ptr,
                                   EVT MemVT, MachineMemOperand *MMO) {
   assert(Chain.getValueType() == MVT::Other && "Invalid chain type");