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2009-12-11beam_bool: Fix generation of code that does not validateBjörn Gustavsson
The following code (by Simon Cornish) bad(XDo1, XDo2, Do3) -> Do1 = (XDo1 =/= []), Do2 = (XDo2 =/= []), CH1 = if Do1 == true; Do1 == false,Do2==false,Do3 == blah -> ch1; true -> no end, CH2 = if Do1 == true; Do1 == false,Do2==false,Do3 == xx -> ch2; true -> no end, {CH1,CH2}. is optimized by beam_bool even though the optimization is not safe. The trouble is that an assignment to {y,0} no longer occurs on all paths leading to its use. The bug is in dst_regs/2 which is supposed to return a set of all registers assigned in a code block, but it ignores registers assigned in 'move' instructions. Fix the bug by taking 'move' instructions into account. This change is safe since it can only cause more registers to be added to the MustBeKilled and MustBeUnused sets in ensure_opt_safe/6, which means that it can only cause the optimization to be turned off for code that used to be optimized.
2009-12-10Fix crash in beam_boolBjörn Gustavsson
The following code crashes beam_bool: bad(XDo1, XDo2, Do3) -> Do1 = (XDo1 =/= []), Do2 = (XDo2 =/= []), if Do1 =:= true; Do1 =:= false, Do2 =:= false, Do3 =:= delete -> no end. (Reported by Simon Cornish; minimized by Kostis Sagonas.) For the moment fix the bug in the simplest and safest way possible (basically, instead of crashing just don't do the optimization). In a future major release (e.g. R14), the following improvements could be considered: * In beam_bool, it should be possible to move the Do1 and Do2 expressions to the pre-block and still optimize the expression in the 'if' statement. * In sys_core_fold, it should be possible to eliminate the try/catch around the guard expression in the 'if', because none of the guard tests can actually fail.
2009-11-20The R13B03 release.OTP_R13B03Erlang/OTP