decompiler  1.0.0
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BlockBasic Class Reference

A basic block for p-code operations. More...

#include <block.hh>

Inheritance diagram for BlockBasic:
FlowBlock

Public Member Functions

 BlockBasic (Funcdata *fd)
 Construct given the underlying function.
 
FuncdatagetFuncdata (void)
 Return the underlying Funcdata object.
 
const FuncdatagetFuncdata (void) const
 Return the underlying Funcdata object.
 
bool contains (const Address &addr) const
 Determine if the given address is contained in the original range.
 
Address getEntryAddr (void) const
 Get the address of the (original) first operation to execute. More...
 
virtual Address getStart (void) const
 Get the starting address of code in this FlowBlock.
 
virtual Address getStop (void) const
 Get the ending address of code in this FlowBlock.
 
virtual block_type getType (void) const
 Get the FlowBlock type of this.
 
virtual FlowBlocksubBlock (int4 i) const
 Get the i-th component block.
 
virtual void saveXmlBody (ostream &s) const
 Save detail about components to an XML stream.
 
virtual void restoreXmlBody (List::const_iterator &iter, List::const_iterator enditer, BlockMap &resolver)
 Restore details about this FlowBlock from an XML stream. More...
 
virtual void printHeader (ostream &s) const
 Print a simple description of this to stream. More...
 
virtual void printRaw (ostream &s) const
 Print raw instructions contained in this FlowBlock.
 
virtual void emit (PrintLanguage *lng) const
 Emit the instructions in this FlowBlock as structured code. More...
 
virtual const FlowBlockgetExitLeaf (void) const
 Get the FlowBlock to which this block exits.
 
virtual PcodeOplastOp (void) const
 Get the last PcodeOp executed by this FlowBlock.
 
virtual bool negateCondition (bool toporbottom)
 Flip the condition computed by this. More...
 
virtual FlowBlockgetSplitPoint (void)
 Get the leaf splitting block. More...
 
virtual int4 flipInPlaceTest (vector< PcodeOp * > &fliplist) const
 Test normalizing the conditional branch in this. More...
 
virtual void flipInPlaceExecute (void)
 Perform the flip to normalize conditional branch executed by this block. More...
 
virtual bool isComplex (void) const
 Is this too complex to be a condition (BlockCondition)
 
bool unblockedMulti (int4 outslot) const
 Check if this block can be removed without introducing inconsistencies. More...
 
bool hasOnlyMarkers (void) const
 Does this block contain only MULTIEQUAL and INDIRECT ops. More...
 
bool isDoNothing (void) const
 Should this block should be removed. More...
 
list< PcodeOp * >::iterator beginOp (void)
 Return an iterator to the beginning of the PcodeOps.
 
list< PcodeOp * >::iterator endOp (void)
 Return an iterator to the end of the PcodeOps.
 
list< PcodeOp * >::const_iterator beginOp (void) const
 Return an iterator to the beginning of the PcodeOps.
 
list< PcodeOp * >::const_iterator endOp (void) const
 Return an iterator to the end of the PcodeOps.
 
bool emptyOp (void) const
 Return true if block contains no operations.
 
- Public Member Functions inherited from FlowBlock
 FlowBlock (void)
 Construct a block with no edges.
 
virtual ~FlowBlock (void)
 Destructor.
 
int4 getIndex (void) const
 Get the index assigned to this block.
 
FlowBlockgetParent (void)
 Get the parent FlowBlock of this.
 
FlowBlockgetImmedDom (void) const
 Get the immediate dominator FlowBlock.
 
FlowBlockgetCopyMap (void) const
 Get the mapped FlowBlock.
 
const FlowBlockgetParent (void) const
 Get the parent FlowBlock of this.
 
uint4 getFlags (void) const
 Get the block_flags properties.
 
virtual void markUnstructured (void)
 Mark target blocks of any unstructured edges.
 
virtual void markLabelBumpUp (bool bump)
 Let hierarchical blocks steal labels of their (first) components. More...
 
virtual void scopeBreak (int4 curexit, int4 curloopexit)
 Mark unstructured edges that should be breaks.
 
virtual void printTree (ostream &s, int4 level) const
 Print tree structure of any blocks owned by this. More...
 
virtual bool preferComplement (Funcdata &data)
 Rearrange this hierarchy to simplify boolean expressions. More...
 
virtual FlowBlocknextFlowAfter (const FlowBlock *bl) const
 Get the leaf FlowBlock that will execute after the given FlowBlock. More...
 
virtual void orderSwitchCases (void) const
 Order case components of any contained BlockSwitch.
 
virtual void saveXmlHeader (ostream &s) const
 Save basic information as XML attributes. More...
 
virtual void restoreXmlHeader (const Element *el)
 Restore basic information for XML attributes. More...
 
void saveXmlEdges (ostream &s) const
 Save edge information to an XML stream. More...
 
void restoreXmlEdges (List::const_iterator &iter, List::const_iterator enditer, BlockMap &resolver)
 Restore edges from an XML stream. More...
 
void saveXml (ostream &s) const
 Write out this to an XML stream. More...
 
void restoreXml (const Element *el, BlockMap &resolver)
 Restore this from an XML stream. More...
 
const FlowBlocknextInFlow (void) const
 Return next block to be executed in flow. More...
 
void setVisitCount (int4 i)
 Set the number of times this block has been visited.
 
int4 getVisitCount (void) const
 Get the count of visits.
 
void setGotoBranch (int4 i)
 Mark a goto branch. More...
 
void setDefaultSwitch (int4 i)
 Mark an edge as the switch default.
 
bool isMark (void) const
 Return true if this block has been marked.
 
void setMark (void)
 Mark this block.
 
void clearMark (void)
 Clear any mark on this block.
 
void setDonothingLoop (void)
 Label this as a do nothing loop.
 
void setDead (void)
 Label this as dead.
 
bool hasSpecialLabel (void) const
 Return true if this uses a different label.
 
bool isJoined (void) const
 Return true if this is a joined basic block.
 
bool isDuplicated (void) const
 Return true if this is a duplicated block.
 
void setLoopExit (int4 i)
 Label the edge exiting this as a loop.
 
void clearLoopExit (int4 i)
 Clear the loop exit edge.
 
void setBackEdge (int4 i)
 Label the back edge of a loop.
 
bool getFlipPath (void) const
 Have out edges been flipped.
 
bool isJumpTarget (void) const
 Return true if non-fallthru jump flows into this. More...
 
FlowBlockgetFalseOut (void) const
 Get the false output FlowBlock.
 
FlowBlockgetTrueOut (void) const
 Get the true output FlowBlock.
 
FlowBlockgetOut (int4 i)
 Get the i-th output FlowBlock.
 
const FlowBlockgetOut (int4 i) const
 Get i-th output FlowBlock.
 
int4 getOutRevIndex (int4 i) const
 Get the input index of the i-th output FlowBlock.
 
FlowBlockgetIn (int4 i)
 Get the i-th input FlowBlock.
 
const FlowBlockgetIn (int4 i) const
 Get the i-th input FlowBlock.
 
int4 getInRevIndex (int4 i) const
 Get the output index of the i-th input FlowBlock.
 
const FlowBlockgetFrontLeaf (void) const
 Get the first leaf FlowBlock. More...
 
FlowBlockgetFrontLeaf (void)
 Get the first leaf FlowBlock. More...
 
int4 calcDepth (const FlowBlock *leaf) const
 Get the depth of the given component FlowBlock. More...
 
int4 sizeOut (void) const
 Get the number of out edges.
 
int4 sizeIn (void) const
 Get the number of in edges.
 
bool hasLoopIn (void) const
 Is there a looping edge coming into this block. More...
 
bool hasLoopOut (void) const
 Is there a looping edge going out of this block. More...
 
bool isLoopIn (int4 i) const
 Is the i-th incoming edge a loop edge.
 
bool isLoopOut (int4 i) const
 Is the i-th outgoing edge a loop edge.
 
int4 getInIndex (const FlowBlock *bl) const
 Get the incoming edge index for the given FlowBlock. More...
 
int4 getOutIndex (const FlowBlock *bl) const
 Get the outgoing edge index for the given FlowBlock. More...
 
bool isDefaultBranch (int4 i) const
 Is the i-th out edge the switch default edge.
 
bool isLabelBumpUp (void) const
 Are labels for this printed by the parent.
 
bool isUnstructuredTarget (void) const
 Is this the target of an unstructured goto.
 
bool isInteriorGotoTarget (void) const
 Is there an unstructured goto to this block's interior.
 
bool hasInteriorGoto (void) const
 Is there an unstructured goto out of this block's interior.
 
bool isEntryPoint (void) const
 Is the entry point of the function.
 
bool isSwitchOut (void) const
 Is this a switch block.
 
bool isDonothingLoop (void) const
 Is this a do nothing block.
 
bool isDead (void) const
 Is this block dead.
 
bool isTreeEdgeIn (int4 i) const
 Is the i-th incoming edge part of the spanning tree.
 
bool isBackEdgeIn (int4 i) const
 Is the i-th incoming edge a back edge.
 
bool isBackEdgeOut (int4 i) const
 Is the i-th outgoing edge a back edge.
 
bool isIrreducibleOut (int4 i) const
 Is the i-th outgoing edge an irreducible edge.
 
bool isIrreducibleIn (int4 i) const
 Is the i-th incoming edge an irreducible edge.
 
bool isDecisionOut (int4 i) const
 Can this and the i-th output be merged into a BlockIf or BlockList.
 
bool isDecisionIn (int4 i) const
 Can this and the i-th input be merged into a BlockIf or BlockList.
 
bool isLoopDAGOut (int4 i) const
 Is the i-th outgoing edge part of the DAG sub-graph.
 
bool isLoopDAGIn (int4 i) const
 Is the i-th incoming edge part of the DAG sub-graph.
 
bool isGotoIn (int4 i) const
 Is the i-th incoming edge unstructured.
 
bool isGotoOut (int4 i) const
 Is the i-th outgoing edge unstructured.
 
JumpTablegetJumptable (void) const
 Get the JumpTable associated this block. More...
 

Static Public Member Functions

static bool noInterveningStatement (PcodeOp *first, int4 path, PcodeOp *last)
 Check if there is meaningful activity between two branch instructions. More...
 
- Static Public Member Functions inherited from FlowBlock
static block_type nameToType (const string &name)
 Get the block_type associated with a name string. More...
 
static string typeToName (block_type bt)
 Get the name string associated with a block_type. More...
 
static bool compareBlockIndex (const FlowBlock *bl1, const FlowBlock *bl2)
 Compare FlowBlock by index. More...
 
static bool compareFinalOrder (const FlowBlock *bl1, const FlowBlock *bl2)
 Final FlowBlock comparison. More...
 
static FlowBlockfindCommonBlock (FlowBlock *bl1, FlowBlock *bl2)
 Find the common dominator of two FlowBlocks. More...
 

Private Member Functions

void insert (list< PcodeOp * >::iterator iter, PcodeOp *inst)
 Insert p-code operation at a given position. More...
 
void setInitialRange (const Address &beg, const Address &end)
 Set the initial address range of the block. More...
 
void copyRange (const BlockBasic *bb)
 Copy address ranges from another basic block.
 
void mergeRange (const BlockBasic *bb)
 Merge address ranges from another basic block.
 
void setOrder (void)
 Reset the SeqNum::order field for all PcodeOp objects in this block. More...
 
void removeOp (PcodeOp *inst)
 Remove PcodeOp from this basic block. More...
 

Private Attributes

list< PcodeOp * > op
 The sequence of p-code operations.
 
Funcdatadata
 The function of which this block is a part.
 
RangeList cover
 Original range of addresses covered by this basic block.
 

Friends

class Funcdata
 

Additional Inherited Members

- Public Types inherited from FlowBlock
enum  block_type {
  t_plain, t_basic, t_graph, t_copy,
  t_goto, t_multigoto, t_ls, t_condition,
  t_if, t_whiledo, t_dowhile, t_switch,
  t_infloop
}
 The possible block types.
 
enum  block_flags {
  f_goto_goto = 1, f_break_goto = 2, f_continue_goto = 4, f_switch_out = 0x10,
  f_unstructured_targ = 0x20, f_mark = 0x80, f_mark2 = 0x100, f_entry_point = 0x200,
  f_interior_gotoout = 0x400, f_interior_gotoin = 0x800, f_label_bumpup = 0x1000, f_donothing_loop = 0x2000,
  f_dead = 0x4000, f_whiledo_overflow = 0x8000, f_flip_path = 0x10000, f_joined_block = 0x20000,
  f_duplicate_block = 0x40000
}
 Boolean properties of blocks. More...
 
enum  edge_flags {
  f_goto_edge = 1, f_loop_edge = 2, f_defaultswitch_edge = 4, f_irreducible = 8,
  f_tree_edge = 0x10, f_forward_edge = 0x20, f_cross_edge = 0x40, f_back_edge = 0x80,
  f_loop_exit_edge = 0x100
}
 Boolean properties on edges. More...
 
- Protected Member Functions inherited from FlowBlock
void setFlag (uint4 fl)
 Set a boolean property.
 
void clearFlag (uint4 fl)
 Clear a boolean property.
 

Detailed Description

A basic block for p-code operations.

A basic block is a maximal sequence of p-code operations (PcodeOp) that, within the context of a function, always execute starting with the first operation in sequence through in order to the last operation. Any decision points in the control flow of a function manifest as branching operations (BRANCH, CBRANCH, BRANCHIND) that necessarily occur as the last operation in a basic block.

Every Funcdata object implements the control-flow graph of the underlying function using BlockBasic objects as the underlying nodes of the graph. The decompiler structures code by making a copy of this graph and then overlaying a hierarchy of structured nodes on top of it.

The block also keeps track of the original range of addresses of instructions constituting the block. As decompiler transformations progress, the set of addresses associated with the current set of PcodeOps my migrate away from this original range.

Member Function Documentation

◆ emit()

virtual void BlockBasic::emit ( PrintLanguage lng) const
inlinevirtual

Emit the instructions in this FlowBlock as structured code.

This is the main entry point, at the control-flow level, for printing structured code.

Parameters
lngis the PrintLanguage that provides details of the high-level language being printed

Reimplemented from FlowBlock.

References PrintLanguage::emitBlockBasic().

◆ flipInPlaceExecute()

void BlockBasic::flipInPlaceExecute ( void  )
virtual

Perform the flip to normalize conditional branch executed by this block.

This reverses the outgoing edge order in the right basic blocks, but does not modify the instructions directly.

Reimplemented from FlowBlock.

References PcodeOp::fallthru_true, PcodeOp::flipFlag(), FlowBlock::negateCondition(), and op.

Referenced by ActionNormalizeBranches::apply().

◆ flipInPlaceTest()

int4 BlockBasic::flipInPlaceTest ( vector< PcodeOp * > &  fliplist) const
virtual

Test normalizing the conditional branch in this.

Find the set of PcodeOp objects that need to be adjusted to flip the condition this FlowBlock calculates.

Return:

  • 0 if the flip would normalize the condition
  • 1 if the flip doesn't affect normalization of the condition
  • 2 if the flip produces an unnormalized condition
    Parameters
    fliplistwill contain the PcodeOps that need to be adjusted
    Returns
    0 if the condition will be normalized, 1 or 2 otherwise

Reimplemented from FlowBlock.

References PcodeOp::code(), CPUI_CBRANCH, op, and opFlipInPlaceTest().

◆ getEntryAddr()

Address BlockBasic::getEntryAddr ( void  ) const

Get the address of the (original) first operation to execute.

This relies slightly on normal semantics: when instructions fall-thru during execution, the associated address increases.

Returns
the address of the original entry point instruction for this block

References cover, Range::getFirstAddr(), RangeList::getFirstRange(), RangeList::getRange(), RangeList::numRanges(), and op.

Referenced by PrintC::emitLabel().

◆ getSplitPoint()

FlowBlock * BlockBasic::getSplitPoint ( void  )
virtual

Get the leaf splitting block.

If this block ends with a conditional branch, return the deepest component block that performs the split. This component needs to be able to perform flipInPlaceTest() and flipInPlaceExecute()

Returns
the component FlowBlock or NULL if this doesn't end in a conditional branch

Reimplemented from FlowBlock.

References FlowBlock::sizeOut().

◆ hasOnlyMarkers()

bool BlockBasic::hasOnlyMarkers ( void  ) const

Does this block contain only MULTIEQUAL and INDIRECT ops.

This is a crucial test for whether this block is doing anything substantial or is a candidate for removal. Even blocks that "do nothing" have some kind of branch and placeholder operations (MULTIEQUAL and INDIRECT) for data flowing through the block. This tests if there is any other operation going on.

Returns
true if there only MULTIEQUAL, INDIRECT, and branch operations in this

References PcodeOp::isBranch(), PcodeOp::isMarker(), and op.

Referenced by isDoNothing(), and noInterveningStatement().

◆ insert()

void BlockBasic::insert ( list< PcodeOp * >::iterator  iter,
PcodeOp inst 
)
private

Insert p-code operation at a given position.

The operation is inserted before the PcodeOp pointed at by the iterator. This method also assigns the ordering index for the PcodeOp, getSeqNum().getOrder()

Parameters
iterpoints at the PcodeOp to insert before
instis the PcodeOp to insert

References PcodeOp::code(), CPUI_BRANCHIND, FlowBlock::f_switch_out, PcodeOp::isBranch(), op, PcodeOp::setBasicIter(), FlowBlock::setFlag(), PcodeOp::setOrder(), setOrder(), and PcodeOp::setParent().

Referenced by Funcdata::opInsert().

◆ isDoNothing()

bool BlockBasic::isDoNothing ( void  ) const

Should this block should be removed.

Check if this block is doing anything useful.

Returns
true if the block does nothing and should be removed

References PcodeOp::code(), CPUI_BRANCHIND, FlowBlock::getIn(), FlowBlock::getOut(), hasOnlyMarkers(), FlowBlock::isSwitchOut(), lastOp(), FlowBlock::sizeIn(), and FlowBlock::sizeOut().

◆ negateCondition()

bool BlockBasic::negateCondition ( bool  toporbottom)
virtual

Flip the condition computed by this.

Flip the order of outgoing edges (at least). This should also affect the original op causing the condition. Note: we don't have to flip at all levels of the hierarchy only at the top and at the bottom

Parameters
toporbottomis true if this is the top outermost block of the hierarchy getting negated
Returns
true if a change was made to data-flow

Reimplemented from FlowBlock.

References PcodeOp::boolean_flip, PcodeOp::fallthru_true, PcodeOp::flipFlag(), FlowBlock::negateCondition(), and op.

◆ noInterveningStatement()

bool BlockBasic::noInterveningStatement ( PcodeOp first,
int4  path,
PcodeOp last 
)
static

Check if there is meaningful activity between two branch instructions.

The first branch is assumed to be a CBRANCH one edge of which flows into the other branch. The flow can be through 1 or 2 blocks. If either block performs an operation other than MULTIEQUAL, INDIRECT (or the branch), then return false.

Parameters
firstis the CBRANCH operation
pathis the index of the edge to follow to the other branch
lastis the other branch operation
Returns
true if there is no meaningful activity

References FlowBlock::getOut(), PcodeOp::getParent(), hasOnlyMarkers(), and FlowBlock::sizeOut().

◆ printHeader()

void BlockBasic::printHeader ( ostream &  s) const
virtual

Print a simple description of this to stream.

Only print a header for this single block

Parameters
sis the output stream

Reimplemented from FlowBlock.

References FlowBlock::printHeader().

Referenced by printRaw().

◆ removeOp()

void BlockBasic::removeOp ( PcodeOp inst)
private

Remove PcodeOp from this basic block.

Parameters
instis the PcodeOp to remove, which must be in the block

References PcodeOp::basiciter, op, and PcodeOp::setParent().

Referenced by Funcdata::opDestroy(), and Funcdata::opUninsert().

◆ restoreXmlBody()

void BlockBasic::restoreXmlBody ( List::const_iterator &  iter,
List::const_iterator  enditer,
BlockMap resolver 
)
virtual

Restore details about this FlowBlock from an XML stream.

Parameters
iteris an iterator to XML elements containing component tags etc.
enditermarks the end of the XML tags
resolveris used to recover FlowBlock objects based on XML references

Reimplemented from FlowBlock.

References cover, BlockMap::getAddressManager(), and RangeList::restoreXml().

◆ setInitialRange()

void BlockBasic::setInitialRange ( const Address beg,
const Address end 
)
private

Set the initial address range of the block.

In terms of machine instructions, a basic block always covers a range of addresses, from its first instruction to its last. This method establishes that range.

Parameters
begis the address of the first instruction in the block
endis the address of the last instruction in the block

References RangeList::clear(), cover, Address::getOffset(), Address::getSpace(), and RangeList::insertRange().

Referenced by Funcdata::nodeJoinCreateBlock(), and Funcdata::setBasicBlockRange().

◆ setOrder()

void BlockBasic::setOrder ( void  )
private

Reset the SeqNum::order field for all PcodeOp objects in this block.

The SeqNum::order field for each PcodeOp must mirror the ordering of that PcodeOp within this block. Insertions are usually handled by calculating an appropriate SeqNum::order field for the new PcodeOp, but sometime there isn't enough room between existing ops. This method is then called to recalculate the SeqNum::order field for all PcodeOp objects in this block, reestablishing space between the field values.

References op.

Referenced by insert(), and Funcdata::spliceBlockBasic().

◆ unblockedMulti()

bool BlockBasic::unblockedMulti ( int4  outslot) const

Check if this block can be removed without introducing inconsistencies.

Does removing this block leads to redundant MULTIEQUAL entries which are inconsistent. A MULTIEQUAL can hide an implied copy, in which case this block is actually doing something and shouldn't be removed.

Parameters
outslotis the index of the outblock that this is getting collapsed to
Returns
true if there is no implied COPY

References PcodeOp::code(), CPUI_MULTIEQUAL, Varnode::getDef(), PcodeOp::getIn(), FlowBlock::getIn(), FlowBlock::getInIndex(), FlowBlock::getOut(), PcodeOp::getParent(), Varnode::isWritten(), op, FlowBlock::sizeIn(), and FlowBlock::sizeOut().


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