class ImplicitControlFlowTracking

Declaration

class ImplicitControlFlowTracking
    : public InstructionPrecedenceTracking { /* full declaration omitted */ };

Description

This class allows to keep track on instructions with implicit control flow. These are instructions that may not pass execution to their successors. For example, throwing calls and guards do not always do this. If we need to know for sure that some instruction is guaranteed to execute if the given block is reached, then we need to make sure that there is no implicit control flow instruction (ICFI) preceding it. For example, this check is required if we perform PRE moving non-speculable instruction to other place.

Declared at: llvm/include/llvm/Analysis/InstructionPrecedenceTracking.h:97

Inherits from: InstructionPrecedenceTracking

Method Overview

• public ImplicitControlFlowTracking(llvm::DominatorTree * DT)
• public const llvm::Instruction * getFirstICFI(const llvm::BasicBlock * BB)
• public bool hasICF(const llvm::BasicBlock * BB)
• public bool isDominatedByICFIFromSameBlock(const llvm::Instruction * Insn)
• public virtual bool isSpecialInstruction(const llvm::Instruction * Insn) const

Inherited from InstructionPrecedenceTracking:

• public clear
• protected getFirstSpecialInstruction
• protected hasSpecialInstructions
• public insertInstructionTo
• protected isPreceededBySpecialInstruction
• protected isSpecialInstruction
• public removeInstruction

Methods

¶ImplicitControlFlowTracking(
    llvm::DominatorTree* DT)

Declared at: llvm/include/llvm/Analysis/InstructionPrecedenceTracking.h:99

Parameters

llvm::DominatorTree* DT

¶const llvm::Instruction* getFirstICFI(
    const llvm::BasicBlock* BB)

Description

Returns the topmost instruction with implicit control flow from the given basic block. Returns nullptr if there is no such instructions in the block.

Declared at: llvm/include/llvm/Analysis/InstructionPrecedenceTracking.h:104

Parameters

const llvm::BasicBlock* BB

¶bool hasICF(const llvm::BasicBlock* BB)

Description

Returns true if at least one instruction from the given basic block has implicit control flow.

Declared at: llvm/include/llvm/Analysis/InstructionPrecedenceTracking.h:110

Parameters

const llvm::BasicBlock* BB

¶bool isDominatedByICFIFromSameBlock(
    const llvm::Instruction* Insn)

Description

Returns true if the first ICFI of Insn's block exists and dominates Insn.

Declared at: llvm/include/llvm/Analysis/InstructionPrecedenceTracking.h:115

Parameters

const llvm::Instruction* Insn

¶virtual bool isSpecialInstruction(
    const llvm::Instruction* Insn) const

Description

A predicate that defines whether or not the instruction \p Insn is considered special and needs to be tracked. Implementing this method in children classes allows to implement tracking of implicit control flow, memory writing instructions or any other kinds of instructions we might be interested in.

Declared at: llvm/include/llvm/Analysis/InstructionPrecedenceTracking.h:119

Parameters

const llvm::Instruction* Insn