public static List <BasicBlock> BuildBasicBlocks(List <IInstruction> ops)
{
// collect set of branch targets
HashSet <IInstruction> BranchTargets = new HashSet <IInstruction>();
foreach (IInstruction op in ops)
{
if (op is IJumpInstruction)
{
IJumpInstruction it = op as IJumpInstruction;
BranchTargets.Add(it.Target);
}
else if (op is IBranchInstruction)
{
IBranchInstruction it = op as IBranchInstruction;
BranchTargets.Add(it.IfTarget);
BranchTargets.Add(it.ElseTarget);
}
}
// walk instruction list and split off blocks at branches or branch targets
List <BasicBlock> Blocks = new List <BasicBlock>();
int nInstructions = ops.Count;
int i = 0;
do
{
BasicBlock block = new BasicBlock();
Blocks.Add(block);
do
{
IInstruction op = ops[i++];
block.AddInstruction(op);
op.Block = block;
// stop if we just added a branch/jump op
if (op is IJumpInstruction || op is IBranchInstruction)
{
break;
}
// stop if next instruction is a branch target
if (i < nInstructions && BranchTargets.Contains(ops[i]))
{
break;
}
} while (i < nInstructions);
} while (i < nInstructions);
// construct CFG edges
for (int b = 0; b < Blocks.Count; b++)
{
IInstruction op = Blocks[b].LastInstruction;
if (op is IBranchInstruction)
{
IBranchInstruction branch = op as IBranchInstruction;
if (branch.IfTarget != null)
{
branch.Block.AddSuccessor(branch.IfTarget.Block);
branch.IfTarget.Block.AddPredecessor(branch.Block);
}
if (branch.ElseTarget != null)
{
branch.Block.AddSuccessor(branch.ElseTarget.Block);
branch.ElseTarget.Block.AddPredecessor(branch.Block);
}
}
else if (op is IJumpInstruction)
{
// unconditional branch or jump, add target as one and only successor
IJumpInstruction jmp = op as IJumpInstruction;
if (jmp.Target != null)
{
jmp.Block.AddSuccessor(jmp.Target.Block);
jmp.Target.Block.AddPredecessor(jmp.Block);
}
}
else if (b < Blocks.Count - 1)
{
// Block ends in something other than a branch or jump
// add next block as successor
Blocks[b].AddSuccessor(Blocks[b + 1]);
Blocks[b + 1].AddPredecessor(Blocks[b]);
}
}
return(Blocks);
}
public static List<BasicBlock> BuildBasicBlocks(List<IInstruction> ops)
{
// collect set of branch targets
HashSet<IInstruction> BranchTargets = new HashSet<IInstruction>();
foreach( IInstruction op in ops )
{
if( op is IJumpInstruction )
{
IJumpInstruction it = op as IJumpInstruction;
BranchTargets.Add( it.Target );
}
else if( op is IBranchInstruction )
{
IBranchInstruction it = op as IBranchInstruction;
BranchTargets.Add( it.IfTarget );
BranchTargets.Add( it.ElseTarget );
}
}
// walk instruction list and split off blocks at branches or branch targets
List<BasicBlock> Blocks = new List<BasicBlock>();
int nInstructions = ops.Count;
int i = 0;
do
{
BasicBlock block = new BasicBlock();
Blocks.Add(block);
do
{
IInstruction op = ops[i++];
block.AddInstruction(op);
op.Block = block;
// stop if we just added a branch/jump op
if (op is IJumpInstruction || op is IBranchInstruction)
break;
// stop if next instruction is a branch target
if (i<nInstructions && BranchTargets.Contains(ops[i]))
break;
} while (i < nInstructions);
} while (i < nInstructions);
// construct CFG edges
for( int b=0; b<Blocks.Count; b++ )
{
IInstruction op = Blocks[b].LastInstruction;
if (op is IBranchInstruction)
{
IBranchInstruction branch = op as IBranchInstruction;
if (branch.IfTarget != null)
{
branch.Block.AddSuccessor(branch.IfTarget.Block);
branch.IfTarget.Block.AddPredecessor(branch.Block);
}
if (branch.ElseTarget != null)
{
branch.Block.AddSuccessor(branch.ElseTarget.Block);
branch.ElseTarget.Block.AddPredecessor(branch.Block);
}
}
else if (op is IJumpInstruction)
{
// unconditional branch or jump, add target as one and only successor
IJumpInstruction jmp = op as IJumpInstruction;
if (jmp.Target != null)
{
jmp.Block.AddSuccessor(jmp.Target.Block);
jmp.Target.Block.AddPredecessor(jmp.Block);
}
}
else if ( b < Blocks.Count-1 )
{
// Block ends in something other than a branch or jump
// add next block as successor
Blocks[b].AddSuccessor(Blocks[b + 1]);
Blocks[b + 1].AddPredecessor(Blocks[b]);
}
}
return Blocks;
}
