llvm::RegallocQuery Class Reference

#include <RegisterCoalescer.h>

List of all members.

Public Types
typedef SmallPtrSet< const LiveInterval *, 8 >	IntervalSet
Public Member Functions
virtual	~RegallocQuery ()
virtual bool	interfere (const LiveInterval &a, const LiveInterval &b) const
	Return whether two live ranges interfere.
virtual void	getInterferences (IntervalSet &interferences, const LiveInterval &a) const =0
	Return the set of intervals that interfere with this one.
virtual int	getNumberOfInterferences (const LiveInterval &a) const =0
virtual void	updateDataForMerge (const LiveInterval &a, const LiveInterval &b, const MachineInstr &copy)
virtual bool	isLegalToCoalesce (const MachineInstr &inst) const

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Detailed Description

An abstract interface for register allocators to interact with coalescers

Example:

This is simply an example of how to use the RegallocQuery interface. It is not meant to be used in production.

class LinearScanRegallocQuery : public RegallocQuery { private: const LiveIntervals

public: LinearScanRegallocQuery(LiveIntervals &intervals) : li(intervals) {};

/ This is pretty slow and conservative, but since linear scan / allocation doesn't pre-compute interference information it's / the best we can do. Coalescers are always free to ignore this / and implement their own discovery strategy. See / SimpleRegisterCoalescing for an example. void getInterferences(IntervalSet &interferences, const LiveInterval &a) const { for(LiveIntervals::const_iterator iv = li.begin(), ivend = li.end(); iv != ivend; ++iv) { if (interfere(a, iv->second)) { interferences.insert(&iv->second); } } };

/ This is *really* slow and stupid. See above. int getNumberOfInterferences(const LiveInterval &a) const { IntervalSet intervals; getInterferences(intervals, a); return intervals.size(); }; };

In the allocator:

RegisterCoalescer &coalescer = getAnalysis<RegisterCoalescer>();

We don't reset the coalescer so if it's already been run this takes almost no time. LinearScanRegallocQuery ifd(*li_); coalescer.coalesceFunction(fn, ifd);

Definition at line 107 of file RegisterCoalescer.h.

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Member Typedef Documentation

typedef SmallPtrSet<const LiveInterval *, 8> llvm::RegallocQuery::IntervalSet

Definition at line 109 of file RegisterCoalescer.h.

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Constructor & Destructor Documentation

virtual llvm::RegallocQuery::~RegallocQuery

(

)

[inline, virtual]

Definition at line 111 of file RegisterCoalescer.h.

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Member Function Documentation

virtual bool llvm::RegallocQuery::interfere	(	const LiveInterval &	a,
		const LiveInterval &	b
	)			const [inline, virtual]

Return whether two live ranges interfere.

Definition at line 114 of file RegisterCoalescer.h.

References llvm::LiveInterval::overlaps().

virtual void llvm::RegallocQuery::getInterferences	(	IntervalSet &	interferences,
		const LiveInterval &	a
	)			const [pure virtual]

Return the set of intervals that interfere with this one.

virtual int llvm::RegallocQuery::getNumberOfInterferences

(

const LiveInterval &

a

)

const [pure virtual]

This can often be cheaper than actually returning the interferences.

virtual void llvm::RegallocQuery::updateDataForMerge	(	const LiveInterval &	a,
		const LiveInterval &	b,
		const MachineInstr &	copy
	)			[inline, virtual]

Make any data structure updates necessary to reflect coalescing or other modifications.

Definition at line 130 of file RegisterCoalescer.h.

virtual bool llvm::RegallocQuery::isLegalToCoalesce

(

const MachineInstr &

inst

)

const [inline, virtual]

Allow the register allocator to communicate when it doesn't want a copy coalesced. This may be due to assumptions made by the allocator about various invariants and so this question is a matter of legality, not performance. Performance decisions about which copies to coalesce should be made by the coalescer.

Definition at line 140 of file RegisterCoalescer.h.

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The documentation for this class was generated from the following file:

• RegisterCoalescer.h