> I just implemented something to this effect for our project at Cadence. It > works by > - an assembler/disassebler that can convert a method into a sequence of > messages, one for each of its bytecodes and back > - using the disassembler to obtain labels which occur at the start of each > basic block > - replacing the first bytecode in every basic block with an illegal bytecode, > remembering the pc and its correct bytecode in the method properties > - implementing a method on MethodContext which receives the unknowBytecode > message sent by the VM when it encounters an illegal bytecode > - the method replaces the illegal bytecode with the correct bytecode, > removing the entry from properties, and continues > > The JIT refuses to compile methods that contain illegal bytecodes so this > runs at interpreter speed until a method no longer contains illegal bytecodes > (has been completely covered). But the illegal bytecode is executed at most > once for each basic block, since it is replaced immediately it is executed. > The information remaining in properties is that of the basic blocks that have > not been executed. > > In the Squeak/Pharo bytecode set there are three unknown bytecodes, 126, 127 > & 139. I have a Monticello package and tests if you're interested.
Yes please. I am interested! Alexandre -- _,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;: Alexandre Bergel http://www.bergel.eu ^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;.
