third_party/llvm-7.0/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp - SwiftShader - Git at Google

 //===-- RISCVISelDAGToDAG.cpp - A dag to dag inst selector for RISCV ------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines an instruction selector for the RISCV target.
 //
 //===----------------------------------------------------------------------===//

 #include "RISCV.h"
 #include "MCTargetDesc/RISCVMCTargetDesc.h"
 #include "RISCVTargetMachine.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/SelectionDAGISel.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;

 #define DEBUG_TYPE "riscv-isel"

 // RISCV-specific code to select RISCV machine instructions for
 // SelectionDAG operations.
 namespace {
 class RISCVDAGToDAGISel final : public SelectionDAGISel {
   const RISCVSubtarget *Subtarget;

 public:
   explicit RISCVDAGToDAGISel(RISCVTargetMachine &TargetMachine)
       : SelectionDAGISel(TargetMachine) {}

   StringRef getPassName() const override {
     return "RISCV DAG->DAG Pattern Instruction Selection";
   }

   bool runOnMachineFunction(MachineFunction &MF) override {
     Subtarget = &MF.getSubtarget<RISCVSubtarget>();
     return SelectionDAGISel::runOnMachineFunction(MF);
   }

   void PostprocessISelDAG() override;

   void Select(SDNode *Node) override;

   bool SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
                                     std::vector<SDValue> &OutOps) override;

   bool SelectAddrFI(SDValue Addr, SDValue &Base);

 // Include the pieces autogenerated from the target description.
 #include "RISCVGenDAGISel.inc"

 private:
   void doPeepholeLoadStoreADDI();
   void doPeepholeBuildPairF64SplitF64();
 };
 }

 void RISCVDAGToDAGISel::PostprocessISelDAG() {
   doPeepholeLoadStoreADDI();
   doPeepholeBuildPairF64SplitF64();
 }

 void RISCVDAGToDAGISel::Select(SDNode *Node) {
   unsigned Opcode = Node->getOpcode();
   MVT XLenVT = Subtarget->getXLenVT();

   // If we have a custom node, we have already selected
   if (Node->isMachineOpcode()) {
     LLVM_DEBUG(dbgs() << "== "; Node->dump(CurDAG); dbgs() << "\n");
     Node->setNodeId(-1);
     return;
   }

   // Instruction Selection not handled by the auto-generated tablegen selection
   // should be handled here.
   EVT VT = Node->getValueType(0);
   if (Opcode == ISD::Constant && VT == XLenVT) {
     auto *ConstNode = cast<ConstantSDNode>(Node);
     // Materialize zero constants as copies from X0. This allows the coalescer
     // to propagate these into other instructions.
     if (ConstNode->isNullValue()) {
       SDValue New = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), SDLoc(Node),
                                            RISCV::X0, XLenVT);
       ReplaceNode(Node, New.getNode());
       return;
     }
   }
   if (Opcode == ISD::FrameIndex) {
     SDLoc DL(Node);
     SDValue Imm = CurDAG->getTargetConstant(0, DL, XLenVT);
     int FI = cast<FrameIndexSDNode>(Node)->getIndex();
     EVT VT = Node->getValueType(0);
     SDValue TFI = CurDAG->getTargetFrameIndex(FI, VT);
     ReplaceNode(Node, CurDAG->getMachineNode(RISCV::ADDI, DL, VT, TFI, Imm));
     return;
   }

   // Select the default instruction.
   SelectCode(Node);
 }

 bool RISCVDAGToDAGISel::SelectInlineAsmMemoryOperand(
     const SDValue &Op, unsigned ConstraintID, std::vector<SDValue> &OutOps) {
   switch (ConstraintID) {
   case InlineAsm::Constraint_i:
   case InlineAsm::Constraint_m:
     // We just support simple memory operands that have a single address
     // operand and need no special handling.
     OutOps.push_back(Op);
     return false;
   default:
     break;
   }

   return true;
 }

 bool RISCVDAGToDAGISel::SelectAddrFI(SDValue Addr, SDValue &Base) {
   if (auto FIN = dyn_cast<FrameIndexSDNode>(Addr)) {
     Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), Subtarget->getXLenVT());
     return true;
   }
   return false;
 }

 // Merge an ADDI into the offset of a load/store instruction where possible.
 // (load (add base, off), 0) -> (load base, off)
 // (store val, (add base, off)) -> (store val, base, off)
 void RISCVDAGToDAGISel::doPeepholeLoadStoreADDI() {
   SelectionDAG::allnodes_iterator Position(CurDAG->getRoot().getNode());
   ++Position;

   while (Position != CurDAG->allnodes_begin()) {
     SDNode *N = &*--Position;
     // Skip dead nodes and any non-machine opcodes.
     if (N->use_empty() || !N->isMachineOpcode())
       continue;

     int OffsetOpIdx;
     int BaseOpIdx;

     // Only attempt this optimisation for I-type loads and S-type stores.
     switch (N->getMachineOpcode()) {
     default:
       continue;
     case RISCV::LB:
     case RISCV::LH:
     case RISCV::LW:
     case RISCV::LBU:
     case RISCV::LHU:
     case RISCV::LWU:
     case RISCV::LD:
     case RISCV::FLW:
     case RISCV::FLD:
       BaseOpIdx = 0;
       OffsetOpIdx = 1;
       break;
     case RISCV::SB:
     case RISCV::SH:
     case RISCV::SW:
     case RISCV::SD:
     case RISCV::FSW:
     case RISCV::FSD:
       BaseOpIdx = 1;
       OffsetOpIdx = 2;
       break;
     }

     // Currently, the load/store offset must be 0 to be considered for this
     // peephole optimisation.
     if (!isa<ConstantSDNode>(N->getOperand(OffsetOpIdx)) ||
         N->getConstantOperandVal(OffsetOpIdx) != 0)
       continue;

     SDValue Base = N->getOperand(BaseOpIdx);

     // If the base is an ADDI, we can merge it in to the load/store.
     if (!Base.isMachineOpcode() || Base.getMachineOpcode() != RISCV::ADDI)
       continue;

     SDValue ImmOperand = Base.getOperand(1);

     if (auto Const = dyn_cast<ConstantSDNode>(ImmOperand)) {
       ImmOperand = CurDAG->getTargetConstant(
           Const->getSExtValue(), SDLoc(ImmOperand), ImmOperand.getValueType());
     } else if (auto GA = dyn_cast<GlobalAddressSDNode>(ImmOperand)) {
       ImmOperand = CurDAG->getTargetGlobalAddress(
           GA->getGlobal(), SDLoc(ImmOperand), ImmOperand.getValueType(),
           GA->getOffset(), GA->getTargetFlags());
     } else {
       continue;
     }

     LLVM_DEBUG(dbgs() << "Folding add-immediate into mem-op:\nBase:    ");
     LLVM_DEBUG(Base->dump(CurDAG));
     LLVM_DEBUG(dbgs() << "\nN: ");
     LLVM_DEBUG(N->dump(CurDAG));
     LLVM_DEBUG(dbgs() << "\n");

     // Modify the offset operand of the load/store.
     if (BaseOpIdx == 0) // Load
       CurDAG->UpdateNodeOperands(N, Base.getOperand(0), ImmOperand,
                                  N->getOperand(2));
     else // Store
       CurDAG->UpdateNodeOperands(N, N->getOperand(0), Base.getOperand(0),
                                  ImmOperand, N->getOperand(3));

     // The add-immediate may now be dead, in which case remove it.
     if (Base.getNode()->use_empty())
       CurDAG->RemoveDeadNode(Base.getNode());
   }
 }

 // Remove redundant BuildPairF64+SplitF64 pairs. i.e. cases where an f64 is
 // built of two i32 values, only to be split apart again. This must be done
 // here as a peephole optimisation as the DAG has not been fully legalized at
 // the point BuildPairF64/SplitF64 nodes are created in RISCVISelLowering, so
 // some nodes would not yet have been replaced with libcalls.
 void RISCVDAGToDAGISel::doPeepholeBuildPairF64SplitF64() {
   SelectionDAG::allnodes_iterator Position(CurDAG->getRoot().getNode());
   ++Position;

   while (Position != CurDAG->allnodes_begin()) {
     SDNode *N = &*--Position;
     // Skip dead nodes and any nodes other than SplitF64Pseudo.
     if (N->use_empty() || !N->isMachineOpcode() ||
         !(N->getMachineOpcode() == RISCV::SplitF64Pseudo))
       continue;

     // If the operand to SplitF64 is a BuildPairF64, the split operation is
     // redundant. Just use the operands to BuildPairF64 as the result.
     SDValue F64Val = N->getOperand(0);
     if (F64Val.isMachineOpcode() &&
         F64Val.getMachineOpcode() == RISCV::BuildPairF64Pseudo) {
       LLVM_DEBUG(
           dbgs() << "Removing redundant SplitF64Pseudo and replacing uses "
                     "with BuildPairF64Pseudo operands:\n");
       LLVM_DEBUG(dbgs() << "N:    ");
       LLVM_DEBUG(N->dump(CurDAG));
       LLVM_DEBUG(dbgs() << "F64Val: ");
       LLVM_DEBUG(F64Val->dump(CurDAG));
       LLVM_DEBUG(dbgs() << "\n");
       SDValue From[] = {SDValue(N, 0), SDValue(N, 1)};
       SDValue To[] = {F64Val.getOperand(0), F64Val.getOperand(1)};
       CurDAG->ReplaceAllUsesOfValuesWith(From, To, 2);
     }
   }
   CurDAG->RemoveDeadNodes();
 }

 // This pass converts a legalized DAG into a RISCV-specific DAG, ready
 // for instruction scheduling.
 FunctionPass *llvm::createRISCVISelDag(RISCVTargetMachine &TM) {
   return new RISCVDAGToDAGISel(TM);
 }
	//===-- RISCVISelDAGToDAG.cpp - A dag to dag inst selector for RISCV ------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file defines an instruction selector for the RISCV target.
	//
	//===----------------------------------------------------------------------===//

	#include "RISCV.h"
	#include "MCTargetDesc/RISCVMCTargetDesc.h"
	#include "RISCVTargetMachine.h"
	#include "llvm/CodeGen/MachineFrameInfo.h"
	#include "llvm/CodeGen/SelectionDAGISel.h"
	#include "llvm/Support/Debug.h"
	#include "llvm/Support/MathExtras.h"
	#include "llvm/Support/raw_ostream.h"
	using namespace llvm;

	#define DEBUG_TYPE "riscv-isel"

	// RISCV-specific code to select RISCV machine instructions for
	// SelectionDAG operations.
	namespace {
	class RISCVDAGToDAGISel final : public SelectionDAGISel {
	const RISCVSubtarget *Subtarget;

	public:
	explicit RISCVDAGToDAGISel(RISCVTargetMachine &TargetMachine)
	: SelectionDAGISel(TargetMachine) {}

	StringRef getPassName() const override {
	return "RISCV DAG->DAG Pattern Instruction Selection";
	}

	bool runOnMachineFunction(MachineFunction &MF) override {
	Subtarget = &MF.getSubtarget<RISCVSubtarget>();
	return SelectionDAGISel::runOnMachineFunction(MF);
	}

	void PostprocessISelDAG() override;

	void Select(SDNode *Node) override;

	bool SelectInlineAsmMemoryOperand(const SDValue &Op, unsigned ConstraintID,
	std::vector<SDValue> &OutOps) override;

	bool SelectAddrFI(SDValue Addr, SDValue &Base);

	// Include the pieces autogenerated from the target description.
	#include "RISCVGenDAGISel.inc"

	private:
	void doPeepholeLoadStoreADDI();
	void doPeepholeBuildPairF64SplitF64();
	};
	}

	void RISCVDAGToDAGISel::PostprocessISelDAG() {
	doPeepholeLoadStoreADDI();
	doPeepholeBuildPairF64SplitF64();
	}

	void RISCVDAGToDAGISel::Select(SDNode *Node) {
	unsigned Opcode = Node->getOpcode();
	MVT XLenVT = Subtarget->getXLenVT();

	// If we have a custom node, we have already selected
	if (Node->isMachineOpcode()) {
	LLVM_DEBUG(dbgs() << "== "; Node->dump(CurDAG); dbgs() << "\n");
	Node->setNodeId(-1);
	return;
	}

	// Instruction Selection not handled by the auto-generated tablegen selection
	// should be handled here.
	EVT VT = Node->getValueType(0);
	if (Opcode == ISD::Constant && VT == XLenVT) {
	auto *ConstNode = cast<ConstantSDNode>(Node);
	// Materialize zero constants as copies from X0. This allows the coalescer
	// to propagate these into other instructions.
	if (ConstNode->isNullValue()) {
	SDValue New = CurDAG->getCopyFromReg(CurDAG->getEntryNode(), SDLoc(Node),
	RISCV::X0, XLenVT);
	ReplaceNode(Node, New.getNode());
	return;
	}
	}
	if (Opcode == ISD::FrameIndex) {
	SDLoc DL(Node);
	SDValue Imm = CurDAG->getTargetConstant(0, DL, XLenVT);
	int FI = cast<FrameIndexSDNode>(Node)->getIndex();
	EVT VT = Node->getValueType(0);
	SDValue TFI = CurDAG->getTargetFrameIndex(FI, VT);
	ReplaceNode(Node, CurDAG->getMachineNode(RISCV::ADDI, DL, VT, TFI, Imm));
	return;
	}

	// Select the default instruction.
	SelectCode(Node);
	}

	bool RISCVDAGToDAGISel::SelectInlineAsmMemoryOperand(
	const SDValue &Op, unsigned ConstraintID, std::vector<SDValue> &OutOps) {
	switch (ConstraintID) {
	case InlineAsm::Constraint_i:
	case InlineAsm::Constraint_m:
	// We just support simple memory operands that have a single address
	// operand and need no special handling.
	OutOps.push_back(Op);
	return false;
	default:
	break;
	}

	return true;
	}

	bool RISCVDAGToDAGISel::SelectAddrFI(SDValue Addr, SDValue &Base) {
	if (auto FIN = dyn_cast<FrameIndexSDNode>(Addr)) {
	Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), Subtarget->getXLenVT());
	return true;
	}
	return false;
	}

	// Merge an ADDI into the offset of a load/store instruction where possible.
	// (load (add base, off), 0) -> (load base, off)
	// (store val, (add base, off)) -> (store val, base, off)
	void RISCVDAGToDAGISel::doPeepholeLoadStoreADDI() {
	SelectionDAG::allnodes_iterator Position(CurDAG->getRoot().getNode());
	++Position;

	while (Position != CurDAG->allnodes_begin()) {
	SDNode N = &--Position;
	// Skip dead nodes and any non-machine opcodes.
	if (N->use_empty() \|\| !N->isMachineOpcode())
	continue;

	int OffsetOpIdx;
	int BaseOpIdx;

	// Only attempt this optimisation for I-type loads and S-type stores.
	switch (N->getMachineOpcode()) {
	default:
	continue;
	case RISCV::LB:
	case RISCV::LH:
	case RISCV::LW:
	case RISCV::LBU:
	case RISCV::LHU:
	case RISCV::LWU:
	case RISCV::LD:
	case RISCV::FLW:
	case RISCV::FLD:
	BaseOpIdx = 0;
	OffsetOpIdx = 1;
	break;
	case RISCV::SB:
	case RISCV::SH:
	case RISCV::SW:
	case RISCV::SD:
	case RISCV::FSW:
	case RISCV::FSD:
	BaseOpIdx = 1;
	OffsetOpIdx = 2;
	break;
	}

	// Currently, the load/store offset must be 0 to be considered for this
	// peephole optimisation.
	if (!isa<ConstantSDNode>(N->getOperand(OffsetOpIdx)) \|\|
	N->getConstantOperandVal(OffsetOpIdx) != 0)
	continue;

	SDValue Base = N->getOperand(BaseOpIdx);

	// If the base is an ADDI, we can merge it in to the load/store.
	if (!Base.isMachineOpcode() \|\| Base.getMachineOpcode() != RISCV::ADDI)
	continue;

	SDValue ImmOperand = Base.getOperand(1);

	if (auto Const = dyn_cast<ConstantSDNode>(ImmOperand)) {
	ImmOperand = CurDAG->getTargetConstant(
	Const->getSExtValue(), SDLoc(ImmOperand), ImmOperand.getValueType());
	} else if (auto GA = dyn_cast<GlobalAddressSDNode>(ImmOperand)) {
	ImmOperand = CurDAG->getTargetGlobalAddress(
	GA->getGlobal(), SDLoc(ImmOperand), ImmOperand.getValueType(),
	GA->getOffset(), GA->getTargetFlags());
	} else {
	continue;
	}

	LLVM_DEBUG(dbgs() << "Folding add-immediate into mem-op:\nBase: ");
	LLVM_DEBUG(Base->dump(CurDAG));
	LLVM_DEBUG(dbgs() << "\nN: ");
	LLVM_DEBUG(N->dump(CurDAG));
	LLVM_DEBUG(dbgs() << "\n");

	// Modify the offset operand of the load/store.
	if (BaseOpIdx == 0) // Load
	CurDAG->UpdateNodeOperands(N, Base.getOperand(0), ImmOperand,
	N->getOperand(2));
	else // Store
	CurDAG->UpdateNodeOperands(N, N->getOperand(0), Base.getOperand(0),
	ImmOperand, N->getOperand(3));

	// The add-immediate may now be dead, in which case remove it.
	if (Base.getNode()->use_empty())
	CurDAG->RemoveDeadNode(Base.getNode());
	}
	}

	// Remove redundant BuildPairF64+SplitF64 pairs. i.e. cases where an f64 is
	// built of two i32 values, only to be split apart again. This must be done
	// here as a peephole optimisation as the DAG has not been fully legalized at
	// the point BuildPairF64/SplitF64 nodes are created in RISCVISelLowering, so
	// some nodes would not yet have been replaced with libcalls.
	void RISCVDAGToDAGISel::doPeepholeBuildPairF64SplitF64() {
	SelectionDAG::allnodes_iterator Position(CurDAG->getRoot().getNode());
	++Position;

	while (Position != CurDAG->allnodes_begin()) {
	SDNode N = &--Position;
	// Skip dead nodes and any nodes other than SplitF64Pseudo.
	if (N->use_empty() \|\| !N->isMachineOpcode() \|\|
	!(N->getMachineOpcode() == RISCV::SplitF64Pseudo))
	continue;

	// If the operand to SplitF64 is a BuildPairF64, the split operation is
	// redundant. Just use the operands to BuildPairF64 as the result.
	SDValue F64Val = N->getOperand(0);
	if (F64Val.isMachineOpcode() &&
	F64Val.getMachineOpcode() == RISCV::BuildPairF64Pseudo) {
	LLVM_DEBUG(
	dbgs() << "Removing redundant SplitF64Pseudo and replacing uses "
	"with BuildPairF64Pseudo operands:\n");
	LLVM_DEBUG(dbgs() << "N: ");
	LLVM_DEBUG(N->dump(CurDAG));
	LLVM_DEBUG(dbgs() << "F64Val: ");
	LLVM_DEBUG(F64Val->dump(CurDAG));
	LLVM_DEBUG(dbgs() << "\n");
	SDValue From[] = {SDValue(N, 0), SDValue(N, 1)};
	SDValue To[] = {F64Val.getOperand(0), F64Val.getOperand(1)};
	CurDAG->ReplaceAllUsesOfValuesWith(From, To, 2);
	}
	}
	CurDAG->RemoveDeadNodes();
	}

	// This pass converts a legalized DAG into a RISCV-specific DAG, ready
	// for instruction scheduling.
	FunctionPass *llvm::createRISCVISelDag(RISCVTargetMachine &TM) {
	return new RISCVDAGToDAGISel(TM);
	}