Roman Zippel wrote: > Hi, > > On Wed, 20 Jun 2007, Paolo Bonzini wrote: > > >>> This is one of the places where i slavishly copied what flow did. if >>> you want to change this, go test it on at least 7 platforms and fix all >>> of the problems that it causes. >>> >> I see. Can one of you recap how it relates to the m68k problem, though? :-) >> > > I have basically this sequence of instructions: > > (call_insn 1 (set (%d0) (call ...))) > > (insn 2 (set (x) (%d0))) > > (call_insn 3 (set (%a0) (call ...))) > > ... > > (call_insn/j 5 (set (%a0) (call ...))) > > The immediate problem is that there is no REG_DEAD note generated for insn > 2. reload calls the code in caller-save.c, because some other call > clobbered register is associated with a pseudo and needs to be preserved > across a call. It builds live information based on the REG_DEAD notes and > is confused that %d0 doesn't die in insn 3. > > There is one problem that the live out information in this block is > incorrect, as it includes the return register, but the function is exited > via sibcall and there is no code to set the return register. This is made > a little more complex, as on m68k the return value here is returned in > %d0/%a0, so %d0 is live at the end of the block. > One possible fix is to clear the uses at the edge to the exit (what the > small patch previously posted does). > > The second problem (and the one in discussion right now) is that I think > %d0 should have been clobbered already by any of the later calls, which is > at least what reload and many other passes assume, they had to manually > add this information, if they wanted to use the dataflow information. > > bye, Roman > I am going to plead insanity here and throw myself on the mercy of the court. there is a bug in generating reg dead notes.
i will get a fix out soon. kenny
