[RISCV] Implement EmitTargetCodeForMemset for Xqcilsm

Author: svs-quic

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp

@@ -1845,6 +1845,15 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
     CurDAG->RemoveDeadNode(Node);
     return;
   }
+  case RISCVISD::QC_SETWMI: {
+    SDValue Chain = Node->getOperand(0);
+    SDVTList VTs = Node->getVTList();
+    SDValue Ops[] = {Node->getOperand(1), Node->getOperand(2),
+                     Node->getOperand(3), Node->getOperand(4), Chain};
+    MachineSDNode *New = CurDAG->getMachineNode(RISCV::QC_SETWMI, DL, VTs, Ops);
+    ReplaceNode(Node, New);
+    return;
+  }
   case ISD::INTRINSIC_WO_CHAIN: {
     unsigned IntNo = Node->getConstantOperandVal(0);
     switch (IntNo) {

llvm/lib/Target/RISCV/RISCVInstrInfoXqci.td

@@ -14,6 +14,14 @@
 // Operand and SDNode transformation definitions.
 //===----------------------------------------------------------------------===//
 
+def SDT_StoreMultiple : SDTypeProfile<0, 4, [SDTCisSameAs<0, 1>,
+                                             SDTCisSameAs<1, 3>,
+                                             SDTCisPtrTy<2>,
+                                             SDTCisVT<3, XLenVT>]>;
+
+def qc_setwmi : RVSDNode<"QC_SETWMI", SDT_StoreMultiple,
+                         [SDNPHasChain, SDNPMayStore, SDNPMemOperand]>;
+
 def uimm5nonzero : RISCVOp<XLenVT>,
                    ImmLeaf<XLenVT, [{return (Imm != 0) && isUInt<5>(Imm);}]> {
   let ParserMatchClass = UImmAsmOperand<5, "NonZero">;

llvm/lib/Target/RISCV/RISCVSelectionDAGInfo.cpp

@@ -7,6 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "RISCVSelectionDAGInfo.h"
+#include "RISCVSubtarget.h"
+#include "llvm/CodeGen/SelectionDAG.h"
 
 #define GET_SDNODE_DESC
 #include "RISCVGenSDNodeInfo.inc"
@@ -62,3 +64,102 @@ void RISCVSelectionDAGInfo::verifyTargetNode(const SelectionDAG &DAG,
   }
 #endif
 }
+
+SDValue RISCVSelectionDAGInfo::EmitTargetCodeForMemset(
+    SelectionDAG &DAG, const SDLoc &dl, SDValue Chain, SDValue Dst, SDValue Src,
+    SDValue Size, Align Alignment, bool isVolatile, bool AlwaysInline,
+    MachinePointerInfo DstPtrInfo) const {
+  const RISCVSubtarget &Subtarget =
+      DAG.getMachineFunction().getSubtarget<RISCVSubtarget>();
+  // We currently do this only for Xqcilsm
+  if (!Subtarget.hasVendorXqcilsm())
+    return SDValue();
+
+  // Do this only if we know the size at compile time.
+  ConstantSDNode *ConstantSize = dyn_cast<ConstantSDNode>(Size);
+  if (!ConstantSize)
+    return SDValue();
+
+  uint64_t NumberOfBytesToWrite = ConstantSize->getZExtValue();
+
+  // Do this only if it is word aligned and we write multiple of 4 bytes.
+  if (!((Alignment.value() & 3) == 0 && (NumberOfBytesToWrite & 3) == 0))
+    return SDValue();
+
+  SmallVector<SDValue, 8> OutChains;
+  SDValue SizeWords, OffsetSetwmi;
+  SDValue SrcValueReplicated = DAG.getNode(ISD::ZERO_EXTEND, dl, MVT::i32, Src);
+  int NumberOfWords = NumberOfBytesToWrite / 4;
+
+  // Helper for constructing the QC_SETWMI instruction
+  auto getSetwmiNode = [&](SDValue SizeWords, SDValue OffsetSetwmi) -> SDValue {
+    SDValue Ops[] = {Chain, SrcValueReplicated, Dst, SizeWords, OffsetSetwmi};
+    return DAG.getNode(RISCVISD::QC_SETWMI, dl, MVT::Other, Ops);
+  };
+
+  bool IsZeroVal =
+      isa<ConstantSDNode>(Src) && cast<ConstantSDNode>(Src)->isZero();
+
+  // If i8 type and constant non-zero value.
+  if ((Src.getValueType() == MVT::i8) && !IsZeroVal)
+    // Replicate byte to word by multiplication with 0x01010101.
+    SrcValueReplicated = DAG.getNode(ISD::MUL, dl, MVT::i32, SrcValueReplicated,
+                                     DAG.getConstant(16843009, dl, MVT::i32));
+
+  // We limit a QC_SETWMI to 16 words or less to improve interruptibility.
+  // So for 1-16 words we use a single QC_SETWMI:
+  //
+  // QC_SETWMI reg1, N, 0(reg2)
+  //
+  // For 17-32 words we use two QC_SETWMI's with the first as 16 words and the
+  // second for the remainder:
+  //
+  // QC_SETWMI reg1, 16, 0(reg2)
+  // QC_SETWMI reg1, 32-N, 64(reg2)
+  //
+  // For 33-48 words, we would like to use (16, 16, n), but that means the last
+  // QC_SETWMI needs an offset of 128 which the instruction doesnt support.
+  // So in this case we use a length of 15 for the second instruction and we do
+  // the rest with the third instruction.
+  // This means the maximum inlined number of words is 47 (for now):
+  //
+  // QC_SETWMI R2, R0, 16, 0
+  // QC_SETWMI R2, R0, 15, 64
+  // QC_SETWMI R2, R0, N, 124
+  //
+  // For 48 words or more, call the target independent memset
+  if (NumberOfWords <= 16) {
+    // 1 - 16 words
+    SizeWords = DAG.getTargetConstant(NumberOfWords, dl, MVT::i32);
+    SDValue OffsetSetwmi = DAG.getTargetConstant(0, dl, MVT::i32);
+    return getSetwmiNode(SizeWords, OffsetSetwmi);
+  } else if (NumberOfWords <= 47) {
+    if (NumberOfWords <= 32) {
+      // 17 - 32 words
+      SizeWords = DAG.getTargetConstant(NumberOfWords - 16, dl, MVT::i32);
+      OffsetSetwmi = DAG.getTargetConstant(64, dl, MVT::i32);
+      OutChains.push_back(getSetwmiNode(SizeWords, OffsetSetwmi));
+
+      SizeWords = DAG.getTargetConstant(16, dl, MVT::i32);
+      OffsetSetwmi = DAG.getTargetConstant(0, dl, MVT::i32);
+      OutChains.push_back(getSetwmiNode(SizeWords, OffsetSetwmi));
+    } else {
+      // 33 - 47 words
+      SizeWords = DAG.getTargetConstant(NumberOfWords - 31, dl, MVT::i32);
+      OffsetSetwmi = DAG.getTargetConstant(124, dl, MVT::i32);
+      OutChains.push_back(getSetwmiNode(SizeWords, OffsetSetwmi));
+
+      SizeWords = DAG.getTargetConstant(15, dl, MVT::i32);
+      OffsetSetwmi = DAG.getTargetConstant(64, dl, MVT::i32);
+      OutChains.push_back(getSetwmiNode(SizeWords, OffsetSetwmi));
+
+      SizeWords = DAG.getTargetConstant(16, dl, MVT::i32);
+      OffsetSetwmi = DAG.getTargetConstant(0, dl, MVT::i32);
+      OutChains.push_back(getSetwmiNode(SizeWords, OffsetSetwmi));
+    }
+    return DAG.getNode(ISD::TokenFactor, dl, MVT::Other, OutChains);
+  }
+
+  // >= 48 words. Call target independent memset.
+  return SDValue();
+}

llvm/lib/Target/RISCV/RISCVSelectionDAGInfo.h

@@ -34,6 +34,12 @@ class RISCVSelectionDAGInfo : public SelectionDAGGenTargetInfo {
   void verifyTargetNode(const SelectionDAG &DAG,
                         const SDNode *N) const override;
 
+  SDValue EmitTargetCodeForMemset(SelectionDAG &DAG, const SDLoc &dl,
+                                  SDValue Chain, SDValue Dst, SDValue Src,
+                                  SDValue Size, Align Alignment,
+                                  bool isVolatile, bool AlwaysInline,
+                                  MachinePointerInfo DstPtrInfo) const override;
+
   bool hasPassthruOp(unsigned Opcode) const {
     return GenNodeInfo.getDesc(Opcode).TSFlags & RISCVISD::HasPassthruOpMask;
   }