llvm::LiveVariables::VarInfo Struct Reference

#include <LiveVariables.h>

Collaboration diagram for llvm::LiveVariables::VarInfo:

[legend]

List of all members.

Public Member Functions
	VarInfo ()
bool	removeKill (MachineInstr *MI)
void	dump () const
Public Attributes
BitVector	AliveBlocks
BitVector	UsedBlocks
unsigned	NumUses
std::vector< MachineInstr * >	Kills

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Detailed Description

VarInfo - This represents the regions where a virtual register is live in the program. We represent this with three different pieces of information: the set of blocks in which the instruction is live throughout, the set of blocks in which the instruction is actually used, and the set of non-phi instructions that are the last users of the value.

In the common case where a value is defined and killed in the same block, There is one killing instruction, and AliveBlocks is empty.

Otherwise, the value is live out of the block. If the value is live throughout any blocks, these blocks are listed in AliveBlocks. Blocks where the liveness range ends are not included in AliveBlocks, instead being captured by the Kills set. In these blocks, the value is live into the block (unless the value is defined and killed in the same block) and lives until the specified instruction. Note that there cannot ever be a value whose Kills set contains two instructions from the same basic block.

PHI nodes complicate things a bit. If a PHI node is the last user of a value in one of its predecessor blocks, it is not listed in the kills set, but does include the predecessor block in the AliveBlocks set (unless that block also defines the value). This leads to the (perfectly sensical) situation where a value is defined in a block, and the last use is a phi node in the successor. In this case, AliveBlocks is empty (the value is not live across any blocks) and Kills is empty (phi nodes are not included). This is sensical because the value must be live to the end of the block, but is not live in any successor blocks.

Definition at line 73 of file LiveVariables.h.

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Constructor & Destructor Documentation

llvm::LiveVariables::VarInfo::VarInfo

(

)

[inline]

Definition at line 93 of file LiveVariables.h.

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Member Function Documentation

bool llvm::LiveVariables::VarInfo::removeKill

(

MachineInstr *

MI

)

[inline]

removeKill - Delete a kill corresponding to the specified machine instruction. Returns true if there was a kill corresponding to this instruction, false otherwise.

Definition at line 98 of file LiveVariables.h.

References Kills.

Referenced by llvm::ARMInstrInfo::convertToThreeAddress(), and llvm::LiveVariables::removeVirtualRegistersKilled().

void LiveVariables::VarInfo::dump

(

)

const

Definition at line 53 of file LiveVariables.cpp.

References AliveBlocks, llvm::cerr(), llvm::BitVector::find_first(), llvm::BitVector::find_next(), Kills, and UsedBlocks.

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Member Data Documentation

BitVector llvm::LiveVariables::VarInfo::AliveBlocks

AliveBlocks - Set of blocks in which this value is alive completely through. This is a bit set which uses the basic block number as an index.

Definition at line 78 of file LiveVariables.h.

Referenced by dump(), llvm::LiveVariables::getVarInfo(), llvm::LiveVariables::HandleVirtRegDef(), llvm::LiveVariables::HandleVirtRegUse(), and llvm::LiveVariables::MarkVirtRegAliveInBlock().

BitVector llvm::LiveVariables::VarInfo::UsedBlocks

UsedBlocks - Set of blocks in which this value is actually used. This is a bit set which uses the basic block number as an index.

Definition at line 82 of file LiveVariables.h.

Referenced by dump(), llvm::LiveVariables::getVarInfo(), and llvm::LiveVariables::HandleVirtRegUse().

unsigned llvm::LiveVariables::VarInfo::NumUses

NumUses - Number of uses of this register across the entire function.

Definition at line 86 of file LiveVariables.h.

Referenced by llvm::LiveVariables::HandleVirtRegUse().

std::vector<MachineInstr*> llvm::LiveVariables::VarInfo::Kills

Kills - List of MachineInstruction's which are the last use of this virtual register (kill it) in their basic block.

Definition at line 91 of file LiveVariables.h.

Referenced by llvm::LiveVariables::addVirtualRegisterDead(), llvm::LiveVariables::addVirtualRegisterKilled(), llvm::ARMInstrInfo::convertToThreeAddress(), dump(), llvm::LiveVariables::HandleVirtRegDef(), llvm::LiveVariables::HandleVirtRegUse(), llvm::LiveVariables::MarkVirtRegAliveInBlock(), removeKill(), and llvm::LiveVariables::replaceKillInstruction().

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The documentation for this struct was generated from the following files:

• LiveVariables.h
• LiveVariables.cpp