This is the mail archive of the
mailing list for the GCC project.
Re: Reload bug
> > Hello Jan,
> > I've narrowed down the bug reported as PR optimization/10233, a regression
> > from GCC 3.2 present on the 3.2 branch since 3.2.1 (but latent on all active
> > branches), to this patch
> > Thu Oct 17 17:14:07 CEST 2002 Jan Hubicka <jh at suse dot cz>
> > PR opt/7630
> > * reload.c (reload_inner_reg_of_subreg): New argument output;
> > (push_reload): Update call.
> > We are trying to reload
> > (subreg:SI (reg/v:DI 29 rmm0 ) 4)
> > as the 'in' argument of push_reload.
> > Before your patch, the compiler correctly detected that the whole register
> > needs to be reloaded because we can't access the high part of MMX regs.
> How it did detected that? I believe it is just pessimization masking a
> bug as currently there is no way how to realize that subreg:SI of MMX
> with offset 4 register is not valid (and with offset 0 is).
> Thinking about it again, I think we can rely on HARD_REGNO_NREGS
> and compute how large the inidividular registers really are, but I don't
> think this is used anywhere in the code.
> It should not get recognized earlier than in reload as we should not
> allocate value with subreg undoable in MMX register into MMX register
> (unless rest of insns dictates otherwise). We've chatted about this
> with Richard
Actually I think the problem is just that the patch has never get into
The patch is pretty involved:
* combine.c (simplify_set): Reverse order of ragumetns to
* df.c (df_def_record_1): Likewise.
* recog.c (register_operand): Likewise.
* simplify-rtx.c (simplify_subreg): Likewise.
* hard-reg-set.h (REG_CANNOT_CHANGE_MODE_P): Update use of
* regclass.c (cannot_change_mode_set_regs, invalid_mode_change_p):
* reload.c (push_reload): Likewise.
* alpha.h (CANNOT_CHANGE_MODE_CLASS): Update definition.
* ia64.h (CANNOT_CHANGE_MODE_CLASS): Update definition.
* mips.h (CANNOT_CHANGE_MODE_CLASS): Update definition.
* mips-protos.h (mips_cannot_change_mode_class): Update prototype.
* mips.c (mips_cannot_change_mode_class): Update.
* pa64-regs.h (CANNOT_CHANGE_MODE_CLASS): Update definition.
* rs6000.h (CANNOT_CHANGE_MODE_CLASS): Update definition.
* s390.h (CANNOT_CHANGE_MODE_CLASS): Update definition.
* sh.h (CANNOT_CHANGE_MODE_CLASS): Update definition.
* sh-protos.h (sh_cannot_change_mode_class): Update prototype.
* sh.c (sh_cannot_change_mode_class): Update.
* i386.h (CANNOT_CHANGE_MODE_CLASS): New.
* tm.texi (CANNOT_CHANGE_MODE_CLASS): Update documentation.
and I believe that the MMX suport in 3.2 is in so bad shape that I would
simply close the bugreport claiming that 3.3 fixes that.