/// <summary>
/// RtlGoto transfers control to either a constant destination or
/// a variable destination computed at run-time.
/// </summary>
/// <param name="g"></param>
/// <returns></returns>
public bool VisitGoto(RtlGoto g)
{
var blockFrom = blockCur;
if ((g.Class & RtlClass.Delay) != 0)
{
// Get next instruction cluster.
rtlStream.MoveNext();
ProcessRtlCluster(rtlStream.Current);
}
CallSite site;
scanner.TerminateBlock(blockCur, rtlStream.Current.Address + ric.Length);
var addrTarget = g.Target as Address;
if (addrTarget != null)
{
var impProc = scanner.GetImportedProcedure(addrTarget, this.ric.Address);
if (impProc != null)
{
site = state.OnBeforeCall(stackReg, arch.PointerType.Size);
var sig = impProc.Signature;
var chr = impProc.Characteristics;
if (chr != null && chr.IsAlloca)
{
return(ProcessAlloca(site, impProc));
}
EmitCall(CreateProcedureConstant(impProc), sig, chr, site);
Emit(new ReturnInstruction());
blockCur.Procedure.ControlGraph.AddEdge(blockCur, blockCur.Procedure.ExitBlock);
return(false);
}
if (!program.SegmentMap.IsValidAddress(addrTarget))
{
var jmpSite = state.OnBeforeCall(stackReg, arch.PointerType.Size);
GenerateCallToOutsideProcedure(jmpSite, addrTarget);
Emit(new ReturnInstruction());
blockCur.Procedure.ControlGraph.AddEdge(blockCur, blockCur.Procedure.ExitBlock);
return(false);
}
var trampoline = scanner.GetTrampoline(addrTarget);
if (trampoline != null)
{
var jmpSite = state.OnBeforeCall(stackReg, arch.PointerType.Size);
var sig = trampoline.Signature;
var chr = trampoline.Characteristics;
// Adjust stack to "hide" any pushed return value since
// currently Reko treats the return value as an implicit detail
// of the calling convention. Had the x86 rewriter explicity
// generated code to predecrement the stack pointer
// when encountering CALL instructions this would
// not be necessary.
if (sig.ReturnAddressOnStack != 0)
{
Emit(new Assignment(stackReg, new BinaryExpression(
Operator.IAdd,
stackReg.DataType,
stackReg,
Constant.Word(stackReg.DataType.Size, sig.ReturnAddressOnStack))));
}
EmitCall(CreateProcedureConstant(trampoline), sig, chr, jmpSite);
if (sig.ReturnAddressOnStack != 0)
{
//$TODO: make x86 calls' implicit storage explicit
// to avoid this hacky dance,
Emit(new Assignment(stackReg, new BinaryExpression(
Operator.ISub,
stackReg.DataType,
stackReg,
Constant.Word(stackReg.DataType.Size, sig.ReturnAddressOnStack))));
}
Emit(new ReturnInstruction());
blockCur.Procedure.ControlGraph.AddEdge(blockCur, blockCur.Procedure.ExitBlock);
return(false);
}
var blockTarget = BlockFromAddress(ric.Address, addrTarget, blockCur.Procedure, state);
var blockSource = blockCur.IsSynthesized
? blockCur
: scanner.FindContainingBlock(ric.Address);
EnsureEdge(blockSource.Procedure, blockSource, blockTarget);
if (ric.Address == addrTarget)
{
var bt = BlockFromAddress(ric.Address, addrTarget, blockCur.Procedure, state);
EnsureEdge(blockSource.Procedure, blockFrom, bt);
}
if (blockCur.Statements.Count == 0)
{
//$REVIEW: we insert a statement into empty blocks to satisfy the BlockHasBeenScanned
// predicate. This should be done in a better way; perhaps by keeping track
// of scanned blocks in the Scanner class?
// The recursive scanning of basic blocks does need improvement;
// consider using a similar technique to Shingle scanner, where reachable
// statements are collected first, and basic blocks reconstructed afterwards.
Emit(new GotoInstruction(addrTarget));
}
return(false);
}
if (g.Target is MemoryAccess mem)
{
if (mem.EffectiveAddress is Constant)
{
// jmp [address]
site = state.OnBeforeCall(this.stackReg, 4); //$BUGBUG: hard coded.
Emit(new CallInstruction(g.Target, site));
Emit(new ReturnInstruction());
blockCur.Procedure.ControlGraph.AddEdge(blockCur, blockCur.Procedure.ExitBlock);
return(false);
}
}
if (ProcessIndirectControlTransfer(ric.Address, g))
{
return(false);
}
site = state.OnBeforeCall(this.stackReg, 4); //$BUGBUG: hard coded
Emit(new CallInstruction(g.Target, site));
Emit(new ReturnInstruction());
blockCur.Procedure.ControlGraph.AddEdge(blockCur, blockCur.Procedure.ExitBlock);
return(false);
}
