Class JitReachabilityModel

java.lang.Object

ghidra.pcode.emu.jit.analysis.JitReachabilityModel

public class JitReachabilityModel
extends Object

The p-code block reachability analysis for JIT-accelerated emulation.

The implements the Reachability phase of the JitCompiler using a simple graph traversal. The result is the set of basic blocks and edges that are actually reachable from a passage's entries.

The traversal is seeded with each of the passage's entry points, and then each outbound flow is considered. Consider a conditional branch. The control-flow graph will have two outbound flows, one for the branch case, and one for the fall-through case. It's possible the data-flow phase detected its condition was constant, and so it would be re-written as an unconditional branch or nop, so we must examine the actual JitOp presented, not just the original p-code op, when determining which flows can be taken. We perform this traversal in the downstream direction only.

Constructor Summary

Constructors

Constructor	Description
JitReachabilityModel(JitAnalysisContext context, JitControlFlowModel cfm, JitDataFlowModel dfm)	Create the reachability model

Method Summary

Modifier and Type	Method	Description
void	dumpResult()	For diagnostics: Dump the analysis result to stder
boolean	isReachable(JitControlFlowModel.JitBlock block)	Check whether the given block can be reached
boolean	isTakeable(JitControlFlowModel.BlockFlow flow)	Check whether the given flow can be taken

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

JitReachabilityModel

public JitReachabilityModel(JitAnalysisContext context,
 JitControlFlowModel cfm,
 JitDataFlowModel dfm)

Create the reachability model

Parameters:

context - the analysis context

cfm - the control-flow model

dfm - the data-flow model.

Implementation Notes:

We're being a bit lazy here requiring the DFM, because we use the re-written JitOps so that reachability heeds folded indirect and conditional branches. If we don't want this dependency, we could inspect the folded constants for the ops ourselves.

Method Details

isReachable

public boolean isReachable(JitControlFlowModel.JitBlock block)

Check whether the given block can be reached

Parameters:

block - the block to check

Returns:

true if reachable, i.e., non-removable

isTakeable

public boolean isTakeable(JitControlFlowModel.BlockFlow flow)

Check whether the given flow can be taken

Parameters:

flow - the flow to check

Returns:

true if it can be taken, i.e., analysis must consider this edge.

dumpResult

public void dumpResult()

For diagnostics: Dump the analysis result to stder

See Also:

• JitCompiler.Diag.PRINT_RM