WebAssemblyRegStackify.cpp File Reference (original) (raw)

This file implements a register stacking pass. More...

Functions
	INITIALIZE_PASS (WebAssemblyRegStackify, DEBUG_TYPE, "Reorder instructions to use the WebAssembly value stack", false, false) FunctionPass *llvm

static void	imposeStackOrdering (MachineInstr *MI)

static void	convertImplicitDefToConstZero (MachineInstr MI, MachineRegisterInfo &MRI, const TargetInstrInfo TII, MachineFunction &MF, LiveIntervals &LIS)

static void	queryCallee (const MachineInstr &MI, bool &Read, bool &Write, bool &Effects, bool &StackPointer)

static void	query (const MachineInstr &MI, bool &Read, bool &Write, bool &Effects, bool &StackPointer)

static bool	shouldRematerialize (const MachineInstr &Def, const WebAssemblyInstrInfo *TII)

static MachineInstr *	getVRegDef (unsigned Reg, const MachineInstr *Insert, const MachineRegisterInfo &MRI, const LiveIntervals &LIS)

static bool	hasOneNonDBGUse (unsigned Reg, MachineInstr *Def, MachineRegisterInfo &MRI, MachineDominatorTree &MDT, LiveIntervals &LIS)

static bool	isSafeToMove (const MachineOperand Def, const MachineOperand Use, const MachineInstr *Insert, const WebAssemblyFunctionInfo &MFI, const MachineRegisterInfo &MRI)

static bool	oneUseDominatesOtherUses (unsigned Reg, const MachineOperand &OneUse, const MachineBasicBlock &MBB, const MachineRegisterInfo &MRI, const MachineDominatorTree &MDT, LiveIntervals &LIS, WebAssemblyFunctionInfo &MFI)
	Test whether OneUse, a use of Reg, dominates all of Reg's other uses.

static unsigned	getTeeOpcode (const TargetRegisterClass *RC)
	Get the appropriate tee opcode for the given register class.

static void	shrinkToUses (LiveInterval &LI, LiveIntervals &LIS)

static MachineInstr *	moveForSingleUse (unsigned Reg, MachineOperand &Op, MachineInstr Def, MachineBasicBlock &MBB, MachineInstr Insert, LiveIntervals &LIS, WebAssemblyFunctionInfo &MFI, MachineRegisterInfo &MRI)
	A single-use def in the same block with no intervening memory or register dependencies; move the def down and nest it with the current instruction.

static MachineInstr *	getPrevNonDebugInst (MachineInstr *MI)

static MachineInstr *	rematerializeCheapDef (unsigned Reg, MachineOperand &Op, MachineInstr &Def, MachineBasicBlock &MBB, MachineBasicBlock::instr_iterator Insert, LiveIntervals &LIS, WebAssemblyFunctionInfo &MFI, MachineRegisterInfo &MRI, const WebAssemblyInstrInfo TII, const WebAssemblyRegisterInfo TRI)
	A trivially cloneable instruction; clone it and nest the new copy with the current instruction.

static MachineInstr *	moveAndTeeForMultiUse (unsigned Reg, MachineOperand &Op, MachineInstr Def, MachineBasicBlock &MBB, MachineInstr Insert, LiveIntervals &LIS, WebAssemblyFunctionInfo &MFI, MachineRegisterInfo &MRI, const WebAssemblyInstrInfo *TII)
	A multiple-use def in the same block with no intervening memory or register dependencies; move the def down, nest it with the current instruction, and insert a tee to satisfy the rest of the uses.

This file implements a register stacking pass.

This pass reorders instructions to put register uses and defs in an order such that they form single-use expression trees. Registers fitting this form are then marked as "stackified", meaning references to them are replaced by "push" and "pop" from the value stack.

This is primarily a code size optimization, since temporary values on the value stack don't need to be named.

Definition in file WebAssemblyRegStackify.cpp.

◆ DEBUG_TYPE

#define DEBUG_TYPE "wasm-reg-stackify"

◆ convertImplicitDefToConstZero()

Definition at line 96 of file WebAssemblyRegStackify.cpp.

References assert(), llvm::MachineOperand::CreateFPImm(), llvm::MachineOperand::CreateImm(), llvm::Function::getContext(), llvm::Type::getDoubleTy(), llvm::Type::getFloatTy(), llvm::MachineFunction::getFunction(), llvm::Constant::getNullValue(), llvm_unreachable, MI, MRI, and TII.

◆ getPrevNonDebugInst()

◆ getTeeOpcode()

◆ getVRegDef()

◆ hasOneNonDBGUse()

◆ imposeStackOrdering()

◆ INITIALIZE_PASS()

◆ isSafeToMove()

Definition at line 311 of file WebAssemblyRegStackify.cpp.

References assert(), D, llvm::MachineInstr::defs(), llvm::drop_begin(), llvm::SmallVectorBase< Size_T >::empty(), llvm::MachineBasicBlock::end(), llvm::MachineInstr::getOpcode(), llvm::MachineInstr::getParent(), I, llvm::WebAssembly::isCatch(), MBB, MRI, llvm::MachineInstr::operands(), llvm::SmallVectorTemplateBase< T, bool >::push_back(), query(), llvm::Read, and llvm::Write.

◆ moveAndTeeForMultiUse()

A multiple-use def in the same block with no intervening memory or register dependencies; move the def down, nest it with the current instruction, and insert a tee to satisfy the rest of the uses.

As an illustration, rewrite this:

Reg = INST ... // Def INST ..., Reg, ... // Insert INST ..., Reg, ... INST ..., Reg, ...

to this:

DefReg = INST ... // Def (to become the new Insert) TeeReg, Reg = TEE_... DefReg INST ..., TeeReg, ... // Insert INST ..., Reg, ... INST ..., Reg, ...

with DefReg and TeeReg stackified. This eliminates a local.get from the resulting code.

Definition at line 633 of file WebAssemblyRegStackify.cpp.

References llvm::MachineInstrBuilder::addReg(), llvm::BuildMI(), llvm::WebAssemblyDebugValueManager::cloneSink(), llvm::LiveIntervals::createAndComputeVirtRegInterval(), llvm::dbgs(), llvm::VNInfo::def, llvm::RegState::Define, llvm::MachineInstr::dump(), llvm::LiveRange::FindSegmentContaining(), llvm::LiveIntervals::getInstructionIndex(), llvm::LiveIntervals::getInterval(), llvm::SlotIndex::getRegSlot(), getTeeOpcode(), llvm::getUndefRegState(), llvm::LiveRange::getVNInfoAt(), llvm::LiveIntervals::handleMove(), I, imposeStackOrdering(), llvm::LiveIntervals::InsertMachineInstrInMaps(), llvm::MachineOperand::isDead(), LLVM_DEBUG, MBB, MRI, shrinkToUses(), llvm::WebAssemblyDebugValueManager::sink(), llvm::WebAssemblyFunctionInfo::stackifyVReg(), TII, and llvm::WebAssemblyDebugValueManager::updateReg().