------- Comment #17 from ian at airs dot com 2007-07-02 01:45 ------- Before I tackle the specific questions, let me try to explain the issue that I see. The issue is that during a function the value of the stack pointer register must always be at or below the local variables. An interrupt can occur at any time. On a processor which does not use a separate interrupt stack, the interrupt will push values on the stack and pass control to the kernel. The stack pointer must be set such that when an interrupt pushes values on the stack the local variables are not corrupted. Does that make sense? My hope is that understanding how this has to work will make clear what must be done.
> 1) Do i do this for both the frame_pointer and hard_frame_pointer? I think this kind of dependency will only be relevant after the prologue has set up the stack. Therefore, it is only necessary to consider the hard frame pointer. > 2) There is currently code in the scanning for adding the stack pointer > for call insns. Sure, makes sense. > This code marks that ref so that it is not considered when building log > links for combine. That makes sense too. It doesn't make sense to build log links for the stack pointer for a call instruction; there isn't going to be anything combine. > a) Should I mark the stack pointer ref added for asm's this way? It's not obvious to me that asm's should have an implicit stack pointer ref. But maybe they should, I don't know. If asm's should have an explicit stack pointer ref, then regarding log links you should do whatever is simplest. asm's can not be combined anyhow. > b) Should I mark the stack pointer refs put in for the mems in this way? Yes, I would think so. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32475
