On 06/18/2010 02:59 PM, Georg Lay wrote: > Andrew Haley schrieb: > >>> As i386 doesn' define an abs insn, you won't see this warning on i386 >>> simply because ABS rtx is never generated. I see the second warning for >>> ABS >= 0 on ARM. However, for ARM there is no ABS rtx genereited either, >>> even though arm BE defines abs insn. >> >> The bug, then, is that this abs should never have been generated. >> >>> I think the evil thing is that RTL optimizers do transformations whose >>> correctness depend on the signedness/qualifiers of the operand(s) >>> without even knowing anything about signedness/qualifiers. >> >> I don't think so: abs() is not defined on unsigned operands. > > So the problem locates either in ifcvt.c:noce_try_abs() or in > optabs.c:expand_abs_nojump() because they do not handle flag_trapv resp. > flag_strict_overflow correctly. I think the problem may be in the front end: I don't think that the tree optimizations are supposed to generate illegal code from legal code. > Is this worth a bug report? Definitely. > The point is that no one else can reproduce it because it shows up on a > non-standard machine. Yes, that's awkward. It'd be nice if we could reproduce it elsewhere. Andrew.
