[RISCV] Pattern-match frameindex (#120917)

Author: s-barannikov

llvm/lib/Target/RISCV/GISel/RISCVInstructionSelector.cpp

@@ -131,6 +131,8 @@ class RISCVInstructionSelector : public InstructionSelector {
                       int OpIdx) const;
   void renderImm(MachineInstrBuilder &MIB, const MachineInstr &MI,
                  int OpIdx) const;
+  void renderFrameIndex(MachineInstrBuilder &MIB, const MachineInstr &MI,
+                        int OpIdx) const;
 
   void renderTrailingZeros(MachineInstrBuilder &MIB, const MachineInstr &MI,
                            int OpIdx) const;
@@ -715,14 +717,6 @@ bool RISCVInstructionSelector::select(MachineInstr &MI) {
     MI.setDesc(TII.get(RISCV::PseudoBRIND));
     MI.addOperand(MachineOperand::CreateImm(0));
     return constrainSelectedInstRegOperands(MI, TII, TRI, RBI);
-  case TargetOpcode::G_FRAME_INDEX: {
-    // TODO: We may want to replace this code with the SelectionDAG patterns,
-    // which fail to get imported because it uses FrameAddrRegImm, which is a
-    // ComplexPattern
-    MI.setDesc(TII.get(RISCV::ADDI));
-    MI.addOperand(MachineOperand::CreateImm(0));
-    return constrainSelectedInstRegOperands(MI, TII, TRI, RBI);
-  }
   case TargetOpcode::G_SELECT:
     return selectSelect(MI, MIB);
   case TargetOpcode::G_FCMP:
@@ -859,6 +853,14 @@ void RISCVInstructionSelector::renderImm(MachineInstrBuilder &MIB,
   MIB.addImm(CstVal);
 }
 
+void RISCVInstructionSelector::renderFrameIndex(MachineInstrBuilder &MIB,
+                                                const MachineInstr &MI,
+                                                int OpIdx) const {
+  assert(MI.getOpcode() == TargetOpcode::G_FRAME_INDEX && OpIdx == -1 &&
+         "Expected G_FRAME_INDEX");
+  MIB.add(MI.getOperand(1));
+}
+
 void RISCVInstructionSelector::renderTrailingZeros(MachineInstrBuilder &MIB,
                                                    const MachineInstr &MI,
                                                    int OpIdx) const {

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp

@@ -2531,29 +2531,6 @@ bool RISCVDAGToDAGISel::SelectAddrFrameIndex(SDValue Addr, SDValue &Base,
   return false;
 }
 
-// Select a frame index and an optional immediate offset from an ADD or OR.
-bool RISCVDAGToDAGISel::SelectFrameAddrRegImm(SDValue Addr, SDValue &Base,
-                                              SDValue &Offset) {
-  if (SelectAddrFrameIndex(Addr, Base, Offset))
-    return true;
-
-  if (!CurDAG->isBaseWithConstantOffset(Addr))
-    return false;
-
-  if (auto *FIN = dyn_cast<FrameIndexSDNode>(Addr.getOperand(0))) {
-    int64_t CVal = cast<ConstantSDNode>(Addr.getOperand(1))->getSExtValue();
-    if (isInt<12>(CVal)) {
-      Base = CurDAG->getTargetFrameIndex(FIN->getIndex(),
-                                         Subtarget->getXLenVT());
-      Offset = CurDAG->getSignedTargetConstant(CVal, SDLoc(Addr),
-                                               Subtarget->getXLenVT());
-      return true;
-    }
-  }
-
-  return false;
-}
-
 // Fold constant addresses.
 static bool selectConstantAddr(SelectionDAG *CurDAG, const SDLoc &DL,
                                const MVT VT, const RISCVSubtarget *Subtarget,

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.h

@@ -46,7 +46,6 @@ class RISCVDAGToDAGISel : public SelectionDAGISel {
                                     std::vector<SDValue> &OutOps) override;
 
   bool SelectAddrFrameIndex(SDValue Addr, SDValue &Base, SDValue &Offset);
-  bool SelectFrameAddrRegImm(SDValue Addr, SDValue &Base, SDValue &Offset);
   bool SelectAddrRegImm(SDValue Addr, SDValue &Base, SDValue &Offset,
                         bool IsRV32Zdinx = false);
   bool SelectAddrRegImmRV32Zdinx(SDValue Addr, SDValue &Base, SDValue &Offset) {

llvm/lib/Target/RISCV/RISCVInstrInfo.td

@@ -400,9 +400,6 @@ def uimm6gt32 : ImmLeaf<XLenVT, [{
 }]>;
 
 // Addressing modes.
-// Necessary because a frameindex can't be matched directly in a pattern.
-def FrameAddrRegImm : ComplexPattern<iPTR, 2, "SelectFrameAddrRegImm",
-                                     [frameindex, or, add]>;
 def AddrRegImm : ComplexPattern<iPTR, 2, "SelectAddrRegImm">;
 
 // Return the negation of an immediate value.
@@ -1401,8 +1398,19 @@ def PseudoAddTPRel : Pseudo<(outs GPR:$rd),
 
 /// FrameIndex calculations
 
-def : Pat<(FrameAddrRegImm (iPTR GPR:$rs1), simm12:$imm12),
-          (ADDI GPR:$rs1, simm12:$imm12)>;
+// Transforms frameindex -> tframeindex.
+def to_tframeindex : SDNodeXForm<frameindex, [{
+  return CurDAG->getTargetFrameIndex(N->getIndex(), N->getValueType(0));
+}]>;
+
+def : GICustomOperandRenderer<"renderFrameIndex">,
+      GISDNodeXFormEquiv<to_tframeindex>;
+
+def : Pat<(frameindex:$fi), (ADDI (iPTR (to_tframeindex $fi)), 0)>;
+
+def : Pat<(add_like frameindex:$fi, simm12:$offset),
+          (ADDI (iPTR (to_tframeindex $fi)), simm12:$offset)>;
+
 def GIAddrRegImm :
   GIComplexOperandMatcher<s32, "selectAddrRegImm">,
   GIComplexPatternEquiv<AddrRegImm>;