/// <summary>
/// Having identified the return variable -- if any -- rewrite all
/// return statements to return that variable.
/// </summary>
/// <param name="ssa"></param>
public void RewriteReturns(SsaState ssa)
{
// For each basic block reaching the exit block, get all reaching
// definitions and then either replace the return expression or
// inject out variable assignments as Stores.
var reachingBlocks = ssa.PredecessorPhiIdentifiers(ssa.Procedure.ExitBlock);
var sig = ssa.Procedure.Signature;
foreach (var reachingBlock in reachingBlocks)
{
var block = reachingBlock.Key;
var idRet = sig.ReturnValue;
if (idRet != null && !(idRet.DataType is VoidType))
{
var idStg = reachingBlock.Value
.Where(cb => cb.Storage.Covers(idRet.Storage))
.FirstOrDefault();
SetReturnExpression(ssa, block, idRet, idStg);
}
int insertPos = block.Statements.FindIndex(s => s.Instruction is ReturnInstruction);
Debug.Assert(insertPos >= 0);
foreach (var p in sig.Parameters.Where(p => p.Storage is OutArgumentStorage))
{
var outStg = (OutArgumentStorage)p.Storage;
var idStg = reachingBlock.Value
.Where(cb => cb.Storage == outStg.OriginalIdentifier.Storage)
.FirstOrDefault();
InsertOutArgumentAssignment(
ssa,
p,
idStg?.Expression ?? Constant.Invalid,
block,
insertPos);
++insertPos;
}
}
}