GuardRecord Class Reference

A (putative) switch variable Varnode and a constraint imposed by a CBRANCH. More...

#include <jumptable.hh>

Public Member Functions
	GuardRecord (PcodeOp *bOp, PcodeOp *rOp, int4 path, const CircleRange &rng, Varnode *v)
	Constructor. More...
PcodeOp *	getBranch (void) const
	Get the CBRANCH associated with this guard.
PcodeOp *	getReadOp (void) const
	Get the PcodeOp immediately causing the restriction.
int4	getPath (void) const
	Get the specific path index going towards the switch.
const CircleRange &	getRange (void) const
	Get the range of values causing the switch path to be taken.
void	clear (void)
	Mark this guard as unused.
int4	valueMatch (Varnode *vn2, Varnode *baseVn2, int4 bitsPreserved2) const
	Determine if this guard applies to the given Varnode. More...

Static Public Member Functions
static int4	oneOffMatch (PcodeOp *op1, PcodeOp *op2)
	Return 1 if the two given PcodeOps produce exactly the same value, 0 if otherwise. More...
static Varnode *	quasiCopy (Varnode *vn, int4 &bitsPreserved)
	Compute the source of a quasi-COPY chain for the given Varnode. More...

Private Attributes
PcodeOp *	cbranch
	PcodeOp CBRANCH the branches around the switch.
PcodeOp *	readOp
	The immediate PcodeOp causing the restriction.
int4	indpath
	Specific CBRANCH path going to the switch.
CircleRange	range
	Range of values causing the CBRANCH to take the path to the switch.
Varnode *	vn
	The Varnode being restricted.
Varnode *	baseVn
	Value being (quasi)copied to the Varnode.
int4	bitsPreserved
	Number of bits copied (all other bits are zero)

Detailed Description

A (putative) switch variable Varnode and a constraint imposed by a CBRANCH.

The record constrains a specific Varnode. If the associated CBRANCH is followed along the path that reaches the switch's BRANCHIND, then we have an explicit description of the possible values the Varnode can hold.

Constructor & Destructor Documentation

GuardRecord::GuardRecord	(	PcodeOp *	bOp,
		PcodeOp *	rOp,
		int4	path,
		const CircleRange &	rng,
		Varnode *	v
	)

Constructor.

Parameters

bOp	is the CBRANCH guarding the switch
rOp	is the PcodeOp immediately reading the Varnode
path	is the specific branch to take from the CBRANCH to reach the switch
rng	is the range of values causing the switch path to be taken
v	is the Varnode holding the value controlling the CBRANCH

Member Function Documentation

int4 GuardRecord::oneOffMatch ( PcodeOp *  op1, PcodeOp *  op2  )

static

Return 1 if the two given PcodeOps produce exactly the same value, 0 if otherwise.

We up through only one level of PcodeOp calculation and only for certain binary ops where the second parameter is a constant.

Parameters

op1	is the first given PcodeOp to test
op2	is the second given PcodeOp

Returns

1 if the same value is produced, 0 otherwise

References PcodeOp::code(), CPUI_INT_ADD, CPUI_INT_AND, CPUI_INT_LEFT, CPUI_INT_MULT, CPUI_INT_OR, CPUI_INT_RIGHT, CPUI_INT_SRIGHT, CPUI_INT_XOR, CPUI_SUBPIECE, and PcodeOp::getIn().

Varnode * GuardRecord::quasiCopy ( Varnode *  vn, int4 &  bitsPreserved  )

static

Compute the source of a quasi-COPY chain for the given Varnode.

A value is a quasi-copy if a sequence of PcodeOps producing it always hold the value as the least significant bits of their output Varnode, but the sequence may put other non-zero values in the upper bits. This method computes the earliest ancestor Varnode for which the given Varnode can be viewed as a quasi-copy.

Parameters

vn	is the given Varnode
bitsPreserved	will hold the number of least significant bits preserved by the sequence

Returns

the earliest source of the quasi-copy, which may just be the given Varnode

References PcodeOp::code(), CPUI_COPY, CPUI_INT_AND, CPUI_INT_OR, CPUI_INT_SEXT, CPUI_INT_ZEXT, CPUI_PIECE, CPUI_SUBPIECE, Varnode::getDef(), PcodeOp::getIn(), Varnode::getNZMask(), Varnode::getOffset(), Varnode::getSize(), Varnode::isConstant(), and mostsigbit_set().

Referenced by JumpBasic::calcRange(), and JumpBasic::markFoldableGuards().

int4 GuardRecord::valueMatch	(	Varnode *	vn2,
		Varnode *	baseVn2,
		int4	bitsPreserved2
	)		const

Determine if this guard applies to the given Varnode.

The guard applies if we know the given Varnode holds the same value as the Varnode attached to the guard. So we return:

• 0, if the two Varnodes do not clearly hold the same value.
• 1, if the two Varnodes clearly hold the same value.
• 2, if the two Varnode clearly hold the same value, pending no writes between their defining op.

Parameters

vn2	is the given Varnode being tested against this guard
baseVn2	is the earliest Varnode from which the given Varnode is quasi-copied.
bitsPreserved2	is the number of potentially non-zero bits in the given Varnode

Returns

the matching code 0, 1, or 2

References PcodeOp::code(), CPUI_INT_ADD, CPUI_LOAD, Varnode::getDef(), PcodeOp::getIn(), Varnode::getOffset(), Varnode::isConstant(), and Varnode::isWritten().

Referenced by JumpBasic::calcRange().

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

• jumptable.hh
• jumptable.cc