Package ghidra.pcode.emu.jit.gen.op

Enum Class CBranchOpGen

java.lang.Object

java.lang.Enum<CBranchOpGen>

ghidra.pcode.emu.jit.gen.op.CBranchOpGen

All Implemented Interfaces:

OpGen<JitCBranchOp>, Serializable, Comparable<CBranchOpGen>, Constable

public enum CBranchOpGen
extends Enum<CBranchOpGen>
implements OpGen<JitCBranchOp>

The generator for a cbranch.

First, emits code to load the condition onto the JVM stack.

With an JitPassage.IntBranch record, this looks up the label for the target block and checks if a transition is necessary. If one is necessary, it emits an ifeq with the transition and goto it guards. The ifeq skips to the fall-through case. If a transition is not necessary, it simply emits an ifne to the target label.

With an JitPassage.ExtBranch record, this does the same as BranchOpGen but guarded by an ifeq that skips to the fall-through case.

Nested Class Summary

Nested classes/interfaces inherited from class java.lang.Enum

Enum.EnumDesc<E extends Enum<E>>

Nested classes/interfaces inherited from interface ghidra.pcode.emu.jit.gen.op.OpGen

OpGen.DeadOpResult, OpGen.LiveOpResult, OpGen.OpResult

Enum Constant Summary

Enum Constants

Enum Constant	Description
GEN	The generator singleton

Method Summary

Modifier and Type	Method	Description
<THIS extends JitCompiledPassage> OpGen.LiveOpResult	genRun(Emitter<Emitter.Bot> em, Local<Types.TRef<THIS>> localThis, Local<Types.TInt> localCtxmod, Methods.RetReq<Types.TRef<JitCompiledPassage.EntryPoint>> retReq, JitCodeGenerator<THIS> gen, JitCBranchOp op, JitControlFlowModel.JitBlock block, Scope scope)	Emit bytecode into the run method.
static CBranchOpGen	valueOf(String name)	Returns the enum constant of this class with the specified name.
static CBranchOpGen[]	values()	Returns an array containing the constants of this enum class, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, describeConstable, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Details

GEN

public static final CBranchOpGen GEN

The generator singleton

Method Details

values

public static CBranchOpGen[] values()

Returns an array containing the constants of this enum class, in the order they are declared.

Returns:

an array containing the constants of this enum class, in the order they are declared

valueOf

public static CBranchOpGen valueOf(String name)

Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum class has no constant with the specified name

NullPointerException - if the argument is null

genRun

public <THIS extends JitCompiledPassage>
OpGen.LiveOpResult genRun(Emitter<Emitter.Bot> em,
 Local<Types.TRef<THIS>> localThis,
 Local<Types.TInt> localCtxmod,
 Methods.RetReq<Types.TRef<JitCompiledPassage.EntryPoint>> retReq,
 JitCodeGenerator<THIS> gen,
 JitCBranchOp op,
 JitControlFlowModel.JitBlock block,
 Scope scope)

Emit bytecode into the run method.

This method must emit the code needed to load any input operands, convert them to the appropriate type, perform the actual operation, and then if applicable, store the output operand. The implementations should delegate to JitCodeGenerator.genReadToStack(Emitter, Local, JitVal, ghidra.pcode.emu.jit.analysis.JitType.SimpleJitType, Ext), JitCodeGenerator.genWriteFromStack(Emitter, Local, JitVar, ghidra.pcode.emu.jit.analysis.JitType.SimpleJitType, Ext, Scope) or similar for mp-int types.

Specified by:

genRun in interface OpGen<JitCBranchOp>

Type Parameters:

THIS - the type of the generated passage

Parameters:

em - the emitter typed with the empty stack

localThis - a handle to the local holding the this reference

localCtxmod - a handle to the local holding ctxmod

retReq - an indication of what must be returned by this JitCompiledPassage.run(int) method.

gen - the code generator

op - the p-code op (use-def node) to translate

block - the basic block containing the p-code op

scope - a scope for generating temporary local storage

Returns:

the result of emitting the p-code op's bytecode

Implementation Notes:

In addition to implementing the proper logic for a conditional branch, this contains a special case for synthetic branches created using JitPassage.ExitPcodeOp.cond(AddrCtx). Such synthetic ops are employed to check for context modification at instruction fall through. It's rare, but if there are multiple paths in an instruction's p-code or an injection, where one causes context modification and the other does not, then we must check for context modification at run time.

Conventionally, all PcodeOp.CBRANCH ops should have the condition as its second operand. Our special "conditional exit" does not. The JitDataFlowModel recognizes this and uses JitFailVal for JitCBranchOp.cond(). The "fail" value asserts that it never gets generated, which will ensure we apply special handling here.