RuleDivOpt Class Reference

Convert INT_MULT and shift forms into INT_DIV or INT_SDIV. More...

Inheritance diagram for RuleDivOpt:

Public Member Functions
virtual Rule *	clone (const ActionGroupList &grouplist) const
	Clone the Rule. More...
virtual void	getOpList (vector< uint4 > &oplist) const
	List of op codes this rule operates on. More...
virtual int4	applyOp (PcodeOp *op, Funcdata &data)
	Attempt to apply this Rule. More...
Public Member Functions inherited from Rule
	Rule (const string &g, uint4 fl, const string &nm)
	Construct given group, properties name. More...
bool	checkActionBreak (void)
	Check if an action breakpoint is turned on. More...
virtual void	reset (Funcdata &data)
	Reset this Rule. More...
virtual void	resetStats (void)
	Reset Rule statistics. More...
virtual void	printStatistics (ostream &s) const
	Print statistics for this Rule. More...

Static Public Member Functions
static Varnode *	findForm (PcodeOp *op, int4 &n, uintb &y, int4 &xsize, OpCode &extopc)
	Check for INT_(S)RIGHT and/or SUBPIECE followed by INT_MULT. More...

Static Private Member Functions
static uintb	calcDivisor (uintb n, uint8 y, int4 xsize)
	Calculate the divisor. More...
static void	moveSignBitExtraction (Varnode *firstVn, Varnode *replaceVn, Funcdata &data)
	Replace sign-bit extractions from the first given Varnode with the second Varnode. More...

Additional Inherited Members
Public Types inherited from Rule
enum	typeflags { type_disable = 1, rule_debug = 2, warnings_on = 4, warnings_given = 8 }
	Properties associated with a Rule. More...

Detailed Description

Convert INT_MULT and shift forms into INT_DIV or INT_SDIV.

The unsigned and signed variants are:

• sub( (zext(V)*c)>>n, 0) => V / (2^n/(c-1))
• sub( (sext(V)*c)s>>n, 0) => V s/ (2^n/(c-1))

Member Function Documentation

applyOp()

int4 RuleDivOpt::applyOp ( PcodeOp *  op, Funcdata &  data  )

virtual

Attempt to apply this Rule.

This method contains the main logic for applying the Rule. It must use a given PcodeOp as the point at which the Rule applies. If it does apply, changes are made directly to the function and 1 (non-zero) is returned, otherwise 0 is returned.

Parameters

op	is the given PcodeOp where the Rule may apply
data	is the function to which to apply

Reimplemented from Rule.

References calcDivisor(), CPUI_INT_ADD, CPUI_INT_DIV, CPUI_INT_SDIV, CPUI_INT_SEXT, CPUI_INT_SRIGHT, CPUI_INT_ZEXT, CPUI_SUBPIECE, findForm(), moveSignBitExtraction(), Funcdata::newConstant(), Funcdata::newOp(), Funcdata::newUniqueOut(), Funcdata::opInsertBefore(), Funcdata::opSetInput(), and Funcdata::opSetOpcode().

calcDivisor()

uintb RuleDivOpt::calcDivisor ( uintb  n, uint8  y, int4  xsize  )

staticprivate

Calculate the divisor.

Given the multiplicative encoding y and the n, the power of 2, Compute:

divisor = 2^n / (y-1)

Do some additional checks on the parameters as an optimized encoding of a divisor.

Parameters

n	is the power of 2
y	is the multiplicative coefficient
xsize	is the maximum power of 2

Returns

the divisor or 0 if the checks fail

References power2Divide().

Referenced by applyOp().

clone()

virtual Rule* RuleDivOpt::clone ( const ActionGroupList &  grouplist ) const

inlinevirtual

Clone the Rule.

If this Rule is a member of one of the groups in the grouplist, this returns a clone of the Rule, otherwise NULL is returned.

Parameters

grouplist

is the list of groups being cloned

Returns

the cloned Rule or NULL

Implements Rule.

References ActionGroupList::contains().

findForm()

Varnode * RuleDivOpt::findForm ( PcodeOp *  op, int4 &  n, uintb &  y, int4 &  xsize, OpCode &  extopc  )

static

Check for INT_(S)RIGHT and/or SUBPIECE followed by INT_MULT.

Look for the forms:

• sub(ext(X) * #y,#c) or
• sub(ext(X) * #y,#c) >> n or
• (ext(X) * #y) >> n

Looks for truncation/multiplication consistent with an optimized division. The truncation can come as either a SUBPIECE operation and/or right shifts. The numerand and the amount it has been extended is discovered. The extension can be, but doesn't have to be, an explicit INT_ZEXT or INT_SEXT. If the form doesn't match NULL is returned. If the Varnode holding the extended numerand matches the final operand size, it is returned, otherwise the unextended numerand is returned. The total truncation, the multiplicative constant, the numerand size, and the extension type are all passed back.

Parameters

op	is the root of the expression
n	is the reference that will hold the total number of bits of truncation
y	will hold the multiplicative constant
xsize	will hold the number of (non-zero) bits in the numerand
extopc	holds whether the extension is INT_ZEXT or INT_SEXT

Returns

the extended numerand if possible, or the unextended numerand, or NULL

References count_leading_zeros(), CPUI_INT_MULT, CPUI_INT_RIGHT, CPUI_INT_SEXT, CPUI_INT_SRIGHT, CPUI_INT_ZEXT, CPUI_MAX, and CPUI_SUBPIECE.

Referenced by applyOp().

getOpList()

void RuleDivOpt::getOpList ( vector< uint4 > &  oplist ) const

virtual

List of op codes this rule operates on.

Populate the given array with all possible OpCodes this Rule might apply to. By default, this method returns all possible OpCodes

Parameters

oplist

is the array to populate

Reimplemented from Rule.

References CPUI_INT_RIGHT, CPUI_INT_SRIGHT, and CPUI_SUBPIECE.

moveSignBitExtraction()

void RuleDivOpt::moveSignBitExtraction ( Varnode *  firstVn, Varnode *  replaceVn, Funcdata &  data  )

staticprivate

Replace sign-bit extractions from the first given Varnode with the second Varnode.

Look for either:

• V >> 0x1f
• V s>> 0x1f

Parameters

firstVn	is the first given Varnode
replaceVn	is the Varnode to replace it with in each extraction
data	is the function holding the Varnodes

References CPUI_INT_RIGHT, CPUI_INT_SRIGHT, and Funcdata::opSetInput().

Referenced by applyOp().

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

• ruleaction.hh
• ruleaction.cc