LiveRangeShrink.cpp File Reference

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#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <iterator>
#include <utility>

Go to the source code of this file.

Macros
#define	DEBUG_TYPE   "lrshrink"

Functions
	STATISTIC (NumInstrsHoistedToShrinkLiveRange, "Number of insructions hoisted to shrink live range.")
	INITIALIZE_PASS (LiveRangeShrink, "lrshrink", "Live Range Shrink Pass", false, false) using InstOrderMap
static MachineInstr *	FindDominatedInstruction (MachineInstr &New, MachineInstr *Old, const InstOrderMap &M)
	Returns New if it's dominated by Old, otherwise return Old.
static bool	isCodeMotionBarrier (MachineInstr &MI)
	Returns whether this instruction is considered a code motion barrier by this pass.
static void	BuildInstOrderMap (MachineBasicBlock::iterator Start, InstOrderMap &M)
	Builds Instruction to its dominating order number map M by traversing from instruction Start.

Detailed Description

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This pass moves instructions close to the definition of its operands to shrink live range of the def instruction. The code motion is limited within the basic block. The moved instruction should have 1 def, and more than one uses, all of which are the only use of the def.

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Definition in file LiveRangeShrink.cpp.

Macro Definition Documentation

DEBUG_TYPE

#define DEBUG_TYPE   "lrshrink"

Definition at line 36 of file LiveRangeShrink.cpp.

Function Documentation

BuildInstOrderMap()

static void BuildInstOrderMap ( MachineBasicBlock::iterator  Start, InstOrderMap &  M  )

static

Builds Instruction to its dominating order number map M by traversing from instruction Start.

Definition at line 108 of file LiveRangeShrink.cpp.

References I, isCodeMotionBarrier(), and llvm::make_range().

FindDominatedInstruction()

static MachineInstr * FindDominatedInstruction ( MachineInstr &  New, MachineInstr *  Old, const InstOrderMap &  M  )

static

Returns New if it's dominated by Old, otherwise return Old.

M maintains a map from instruction to its dominating order that satisfies M[A] > M[B] guarantees that A is dominated by B. If New is not in M, return Old. Otherwise if Old is null, return New.

Definition at line 77 of file LiveRangeShrink.cpp.

References I.

INITIALIZE_PASS()

INITIALIZE_PASS	(	LiveRangeShrink	,
		"lrshrink"	,
		"Live Range Shrink Pass"	,
		false	,
		false
	)

isCodeMotionBarrier()

static bool isCodeMotionBarrier ( MachineInstr &  MI )

static

Returns whether this instruction is considered a code motion barrier by this pass.

We can be less conservative than hasUnmodeledSideEffects() when deciding whether an instruction is a barrier because it is known that pseudo probes are safe to move in this pass specifically (see commit 1cb47a063e2b).

Definition at line 102 of file LiveRangeShrink.cpp.

References MI.

Referenced by BuildInstOrderMap().

STATISTIC()

STATISTIC	(	NumInstrsHoistedToShrinkLiveRange	,
		"Number of insructions hoisted to shrink live range."
	)