private BasicBlock BasicBlockFromIndex(int start, Context context)
{
if (start >= context.Block.Count)
throw new InvalidOperationException("run off of end of instructions");
var offset = context.Block[start].Offset;
var i = start;
Func<int, Instructions> extractInclusive = j => context.Block.Peephole(start, j - start + 1, tracer);
Func<int, Instructions> extractExclusive = j => context.Block.Peephole(start, j - start, tracer);
while (i < context.Block.Count)
{
var instruction = context.Block[i];
if (i > start && targets.Contains(instruction.Offset))
{
var jbb = new JumpBasicBlock(nextBlockId++, extractExclusive(i));
context.OffsetToBlock.Add(offset, jbb);
jbb.Target = BasicBlockFromLocalTarget(instruction.Offset, context);
jbb.Target.Sources.Add(jbb);
return jbb;
}
else
{
switch (instruction.Flavor)
{
case InstructionFlavor.Misc:
{
var misci = (MiscInstruction)instruction;
switch (misci.Op)
{
case MiscOp.Throw:
{
var nrbb = new NonReturningBasicBlock(nextBlockId++, extractInclusive(i));
context.OffsetToBlock.Add(offset, nrbb);
return nrbb;
}
case MiscOp.Rethrow:
{
var handlerContext = context as HandlerContext;
if (handlerContext == null ||
!(handlerContext.ILHandler is CatchTryInstructionHandler))
throw new InvalidOperationException("rethrow not within catch");
var nrbb = new NonReturningBasicBlock(nextBlockId++, extractInclusive(i));
context.OffsetToBlock.Add(offset, nrbb);
return nrbb;
}
case MiscOp.Ret:
case MiscOp.RetVal:
{
if (context is TryContext || context is HandlerContext)
throw new InvalidOperationException("return within a try or handler block");
var nrbb = new NonReturningBasicBlock(nextBlockId++, extractInclusive(i));
context.OffsetToBlock.Add(offset, nrbb);
return nrbb;
}
case MiscOp.Endfinally:
{
var handlerContext = context as HandlerContext;
if (handlerContext == null)
throw new InvalidOperationException
("endfinally not within fault/finally block");
switch (handlerContext.ILHandler.Flavor)
{
case HandlerFlavor.Catch:
case HandlerFlavor.Filter:
throw new InvalidOperationException
("endfinally not within fault/finally block");
case HandlerFlavor.Fault:
{
var efbb = new EndFaultBasicBlock
(nextBlockId++,
extractExclusive(i),
(TBBFaultHandler)handlerContext.TBBHandler);
context.OffsetToBlock.Add(offset, efbb);
return efbb;
}
case HandlerFlavor.Finally:
{
var efbb = new EndFinallyBasicBlock
(nextBlockId++,
extractExclusive(i),
(TBBFinallyHandler)handlerContext.TBBHandler,
misci.BeforeState.Depth);
context.OffsetToBlock.Add(offset, efbb);
return efbb;
}
default:
throw new ArgumentOutOfRangeException();
}
}
default:
break;
}
break;
}
case InstructionFlavor.Branch:
{
var bri = (BranchInstruction)instruction;
switch (bri.Op)
{
case BranchOp.Br:
{
var jbb = new JumpBasicBlock(nextBlockId++, extractExclusive(i));
context.OffsetToBlock.Add(offset, jbb);
jbb.Target = BasicBlockFromLocalTarget(bri.Target, context);
jbb.Target.Sources.Add(jbb);
return jbb;
}
case BranchOp.Brtrue:
case BranchOp.Brfalse:
case BranchOp.Breq:
case BranchOp.Brne:
case BranchOp.BrLt:
case BranchOp.BrLe:
case BranchOp.BrGt:
case BranchOp.BrGe:
{
if (i + 1 >= context.Block.Count)
throw new InvalidOperationException("run off end of instructions");
var bbb = new BranchBasicBlock
(nextBlockId++,
extractExclusive(i),
Test.FromBranchOp(bri.Op, bri.IsUnsigned, bri.Type));
context.OffsetToBlock.Add(offset, bbb);
bbb.Target = BasicBlockFromLocalTarget(bri.Target, context);
bbb.Target.Sources.Add(bbb);
bbb.Fallthrough = BasicBlockFromLocalTarget(context.Block[i + 1].Offset, context);
if (!bbb.Fallthrough.Equals(bbb.Target))
bbb.Fallthrough.Sources.Add(bbb);
return bbb;
}
case BranchOp.Leave:
{
var handlerPopCount = default(int);
var stackPopCount = bri.BeforeState.Depth;
var leftContext = default(bool);
var bb = BasicBlockFromTarget
(bri.Target, context, out leftContext, out handlerPopCount);
if (!leftContext)
{
// Not leaving try or handler block, so just empty stack and branch
var lbb = new LeaveBasicBlock
(nextBlockId++, extractExclusive(i), stackPopCount);
context.OffsetToBlock.Add(offset, lbb);
lbb.Target = bb;
lbb.Target.Sources.Add(lbb);
return lbb;
}
else
{
var tryContext = context as TryContext;
if (tryContext != null)
{
// Poping at least one exception handler and branching
var ltbb = new LeaveTryBasicBlock
(nextBlockId++,
extractExclusive(i),
tryContext.TryBasicBlock,
handlerPopCount,
stackPopCount);
context.OffsetToBlock.Add(offset, ltbb);
ltbb.Target = bb;
ltbb.Target.Sources.Add(ltbb);
return ltbb;
}
else
{
var handlerContext = context as HandlerContext;
if (handlerContext != null)
{
switch (handlerContext.ILHandler.Flavor)
{
case HandlerFlavor.Catch:
{
// Poping zero or more exception handlers and branching
var lcbb = new LeaveCatchBasicBlock
(nextBlockId++,
extractExclusive(i),
(TBBCatchHandler)handlerContext.TBBHandler,
handlerPopCount,
stackPopCount);
lcbb.Target = bb;
lcbb.Target.Sources.Add(lcbb);
return lcbb;
}
case HandlerFlavor.Filter:
throw new NotSupportedException("filter");
case HandlerFlavor.Fault:
throw new InvalidOperationException("leaving fault block");
case HandlerFlavor.Finally:
throw new InvalidOperationException("leaving finally block");
default:
throw new ArgumentOutOfRangeException();
}
}
else
throw new InvalidOperationException
("no try or handler context to leave");
}
}
}
default:
throw new ArgumentOutOfRangeException();
}
}
case InstructionFlavor.Switch:
{
if (i + 1 >= context.Block.Count)
throw new InvalidOperationException("run off end of instructions");
var switchi = (SwitchInstruction)instruction;
var sbb = new SwitchBasicBlock(nextBlockId++, extractExclusive(i));
context.OffsetToBlock.Add(offset, sbb);
var seen = new Set<BasicBlock>();
foreach (var t in switchi.CaseTargets)
{
var target = BasicBlockFromLocalTarget(t, context);
sbb.CaseTargets.Add(target);
if (!seen.Contains(target))
{
target.Sources.Add(sbb);
seen.Add(target);
}
}
sbb.Fallthrough = BasicBlockFromLocalTarget(context.Block[i + 1].Offset, context);
if (!seen.Contains(sbb.Fallthrough))
sbb.Fallthrough.Sources.Add(sbb);
return sbb;
}
case InstructionFlavor.Try:
{
// Try is known to be a target, thus i == start and extract(i) would yield empty
var tryi = (TryInstruction)instruction;
var parent = default(TryBasicBlock);
var tryContext = context as TryContext;
if (tryContext != null)
parent = tryContext.TryBasicBlock;
else
{
var handlerContext = context as HandlerContext;
if (handlerContext != null)
parent = handlerContext.TryContext.TryBasicBlock;
}
var tbb = new TryBasicBlock(nextBlockId++, parent, instruction.BeforeState);
context.OffsetToBlock.Add(offset, tbb);
var subTryContext = new TryContext(tryi.Body, context, tbb);
tbb.Body = BasicBlockFromInstructions(subTryContext);
tbb.Body.Sources.Add(tbb);
foreach (var ilHandler in tryi.Handlers)
{
var tbbHandler = default(TBBHandler);
switch (ilHandler.Flavor)
{
case HandlerFlavor.Catch:
{
var catchh = (CatchTryInstructionHandler)ilHandler;
tbbHandler = new TBBCatchHandler(tbb, catchh.Type);
break;
}
case HandlerFlavor.Filter:
throw new NotSupportedException("filter blocks");
case HandlerFlavor.Fault:
{
tbbHandler = new TBBFaultHandler(tbb);
break;
}
case HandlerFlavor.Finally:
{
tbbHandler = new TBBFinallyHandler(tbb);
break;
}
default:
throw new ArgumentOutOfRangeException();
}
var subHandlerContext = new HandlerContext
(ilHandler.Body, ilHandler, subTryContext, tbbHandler);
tbbHandler.Body = BasicBlockFromInstructions(subHandlerContext);
tbbHandler.Body.Sources.Add(tbb);
tbb.Handlers.Add(tbbHandler);
}
return tbb;
}
default:
break;
}
i++;
}
}
throw new InvalidOperationException("ran off of end of instructions");
}
private string TryReduceSwitch(BasicBlock root, SwitchBasicBlock switchbb)
{
// Build a map from basic blocks to the cases which enter it.
// Also collect some simple stats.
var caseMap = new Map<BasicBlock, Set<int>> { { switchbb.Fallthrough, new Set<int> { -1 } } };
var allNonReturning = switchbb.Fallthrough is NonReturningBasicBlock;
var allHaveOneSource = switchbb.Fallthrough.Sources.Count == 1;
var jumpTargets = new Set<BasicBlock>();
var jumpbb = switchbb.Fallthrough as JumpBasicBlock;
if (jumpbb != null)
jumpTargets.Add(jumpbb.Target);
for (var i = 0; i < switchbb.CaseTargets.Count; i++)
{
var t = switchbb.CaseTargets[i];
if (!(t is NonReturningBasicBlock))
allNonReturning = false;
if (t.Sources.Count != 1)
allHaveOneSource = false;
jumpbb = t as JumpBasicBlock;
if (jumpbb != null)
jumpTargets.Add(jumpbb.Target);
var values = default(Set<int>);
if (caseMap.TryGetValue(t, out values))
// Block is shared amongst switch cases
values.Add(i);
else
caseMap.Add(t, new Set<int> { i });
}
if (caseMap.Count == 1)
{
// CASE 1: all switch cases go to the same block, so replace the switch with a pop and jump
var instructions = switchbb.Block.CopyContents();
instructions.Add
(new MiscInstruction(NextInstructionId--, MiscOp.Pop)
{ BeforeState = switchbb.Block.BeforeState, AfterState = switchbb.Fallthrough.Block.BeforeState });
var newbb = new JumpBasicBlock
(nextBlockId++, Peephole(switchbb.Block.BeforeState, instructions), switchbb.Fallthrough);
root.Coalesce(switchbb, new Set<BasicBlock> { switchbb }, newbb);
return string.Format("removed switch at B{0}", switchbb.Id);
}
if (allNonReturning && allHaveOneSource)
{
// CASE 2: all switch cases are non-returning and have one source, so move them all into
// a non-returing block with switch
var group = new Set<BasicBlock> { switchbb };
var cases = new Seq<StructuralCase>();
foreach (var kv in caseMap)
{
cases.Add(new StructuralCase(kv.Value, kv.Key.Block));
group.Add(kv.Key);
}
var ssi = new StructuralSwitchInstruction(NextInstructionId--, switchbb.Block, cases)
{
BeforeState = switchbb.Block.BeforeState,
AfterState = switchbb.Fallthrough.Block.AfterState
};
var newbb = new NonReturningBasicBlock(nextBlockId++, new Instructions(ssi));
root.Coalesce(switchbb, group, newbb);
return String.Format("non-returning structural switch from B{0}", switchbb.Id);
}
if (jumpTargets.Count == 1)
{
var theJumpTarget = jumpTargets[0];
var allIntermediateAreNonReturningOrJumpToTarget = true;
foreach (var kv in caseMap)
{
if (!kv.Key.Equals(theJumpTarget))
{
if (kv.Key.Sources.Count > 1 ||
!(kv.Key is NonReturningBasicBlock || kv.Key is JumpBasicBlock))
allIntermediateAreNonReturningOrJumpToTarget = false;
}
}
if (allIntermediateAreNonReturningOrJumpToTarget)
{
// CASE 3: all switch cases either jump directly to the switch successor or go via jump block,
// or don't return. Inline all the cases and place the switch in a jump to target block
var group = new Set<BasicBlock> { switchbb };
var cases = new Seq<StructuralCase>();
var afterState = default(MachineState);
foreach (var kv in caseMap)
{
var block = default(Instructions);
if (kv.Key.Equals(theJumpTarget))
{
var bci = new BreakContinueInstruction(NextInstructionId--, BreakContinueOp.Break, null)
{
BeforeState = theJumpTarget.Block.BeforeState,
AfterState = theJumpTarget.Block.BeforeState
};
// Fallthrough to final jump target
block = new Instructions(bci);
}
else
{
// Inline case block, and if not non-returning then fallthrough to final jump target
var instructions = kv.Key.Block.CopyContents();
if (!kv.Key.Block.NeverReturns)
{
var bci = new BreakContinueInstruction
(NextInstructionId--, BreakContinueOp.Break, null)
{
BeforeState = kv.Key.Block.AfterState,
AfterState = kv.Key.Block.AfterState
};
instructions.Add(bci);
}
group.Add(kv.Key);
block = new Instructions(kv.Key.Block.BeforeState, instructions);
}
if (afterState == null)
afterState = block.AfterState;
cases.Add(new StructuralCase(kv.Value, block));
}
var ssi = new StructuralSwitchInstruction(NextInstructionId--, switchbb.Block, cases)
{
BeforeState = switchbb.Block.BeforeState,
AfterState = afterState
};
var newbb = new JumpBasicBlock(nextBlockId++, new Instructions(ssi), theJumpTarget);
root.Coalesce(switchbb, group, newbb);
return String.Format("structural switch from B{0}", switchbb.Id);
}
}
return null;
}
