void DetectNullSafeArrayToPointer(BlockContainer container)
{
// Detect the following pattern:
// ...
// stloc V(ldloc S)
// if (comp(ldloc S == ldnull)) br B_null_or_empty
// br B_not_null
// }
// Block B_not_null {
// if (conv i->i4 (ldlen(ldloc V))) br B_not_null_and_not_empty
// br B_null_or_empty
// }
// Block B_not_null_and_not_empty {
// stloc P(ldelema(ldloc V, ldc.i4 0, ...))
// br B_target
// }
// Block B_null_or_empty {
// stloc P(conv i4->u(ldc.i4 0))
// br B_target
// }
// And convert the whole thing into:
// ...
// stloc P(array.to.pointer(V))
// br B_target
bool modified = false;
for (int i = 0; i < container.Blocks.Count; i++)
{
var block = container.Blocks[i];
if (IsNullSafeArrayToPointerPattern(block, out ILVariable v, out ILVariable p, out Block targetBlock))
{
context.Step("NullSafeArrayToPointerPattern", block);
ILInstruction arrayToPointer = new GetPinnableReference(new LdLoc(v), null);
if (p.StackType != StackType.Ref)
{
arrayToPointer = new Conv(arrayToPointer, p.StackType.ToPrimitiveType(), false, Sign.None);
}
block.Instructions[block.Instructions.Count - 2] = new StLoc(p, arrayToPointer)
.WithILRange(block.Instructions[block.Instructions.Count - 2]);
((Branch)block.Instructions.Last()).TargetBlock = targetBlock;
modified = true;
}
}
if (modified)
{
container.Blocks.RemoveAll(b => b.IncomingEdgeCount == 0); // remove blocks made unreachable
}
}
void DetectNullSafeArrayToPointerOrCustomRefPin(BlockContainer container)
{
bool modified = false;
for (int i = 0; i < container.Blocks.Count; i++)
{
var block = container.Blocks[i];
if (IsNullSafeArrayToPointerPattern(block, out ILVariable v, out ILVariable p, out Block targetBlock))
{
context.Step("NullSafeArrayToPointerPattern", block);
ILInstruction arrayToPointer = new GetPinnableReference(new LdLoc(v), null);
if (p.StackType != StackType.Ref)
{
arrayToPointer = new Conv(arrayToPointer, p.StackType.ToPrimitiveType(), false, Sign.None);
}
block.Instructions[block.Instructions.Count - 2] = new StLoc(p, arrayToPointer)
.WithILRange(block.Instructions[block.Instructions.Count - 2]);
((Branch)block.Instructions.Last()).TargetBlock = targetBlock;
modified = true;
}
