2008/5/29 <[EMAIL PROTECTED]>:
> Again thank you and Denis for your comment.
>
> Here is what I deduce from code and Denis comments - I am sure he (and
> others) will correct me if wrong :-)
>
>
> The main issue is that we have one pointer register that cannot take offset
> and two base pointers with limited offset (0-63).
Yes.
Oops I'm sorry. I wrote -63 to +63 in my last mail it's wrong.
The right offset 0 to 63.
>
> Reload provides no means to pick the right pointer register. To do so would
> require a "preffered base pointer" mechanism.
Yes.
>
> AVR L_R_A sole purpose is substituting POINTER class where there are
> oppertunities to do so.
>
> BUT as L_R_A is in middle of find_reloads_address, we have a problem in
> that some normal reload solutions have already been applied and some have
> not.
Yes.
> This may mean that 1) We never get here - so miss POINTER oppertunity or 2)
> Miss even better solutions that are applied latter.
> 3)Have code vulnerable to reload changes.
Yes.
> I have added comment below to explain the parts.
> I'll probably need to add some debug hooks to check what parts still
> contribute.
>
> best regards
>
> Andy
>
>
>
> #define LEGITIMIZE_RELOAD_ADDRESS(X, MODE, OPNUM, TYPE, IND_LEVELS, WIN)
> \
> do { \
> if (1&&(GET_CODE (X) == POST_INC || GET_CODE (X) == PRE_DEC)) \
> { \
> push_reload (XEXP (X,0), XEXP (X,0), &XEXP (X,0), &XEXP (X,0), \
> POINTER_REGS, GET_MODE (X),GET_MODE (X) , 0, 0, \
> OPNUM, RELOAD_OTHER); \
> goto WIN; \
> } \
>
>
> The intent is to use POINTER class registers for INC/DEC so we have one more
> register available than BASE_POINTER
>
> Has INC/DEC been handled already making this part redundant?
> Are there any other solutions that this code skips?
Really, I forgot why this part of L_R_A exists.
Look at strange 'if (1&&'.
I remember that once I have disabled it (add 0&&), but after some
testing I have
enablet it again.
> if (GET_CODE (X) == PLUS \
> && REG_P (XEXP (X, 0)) \
> && GET_CODE (XEXP (X, 1)) == CONST_INT \
> && INTVAL (XEXP (X, 1)) >= 1) \
> { \
> int fit = INTVAL (XEXP (X, 1)) <= (64 - GET_MODE_SIZE (MODE)); \
> if (fit) \
> { \
> if (reg_equiv_address[REGNO (XEXP (X, 0))] != 0) \
> { \
> int regno = REGNO (XEXP (X, 0)); \
> rtx mem = make_memloc (X, regno); \
> push_reload (XEXP (mem,0), NULL, &XEXP (mem,0), NULL, \
> POINTER_REGS, Pmode, VOIDmode, 0, 0, \
> 1, ADDR_TYPE (TYPE)); \
> push_reload (mem, NULL_RTX, &XEXP (X, 0), NULL, \
> BASE_POINTER_REGS, GET_MODE (X), VOIDmode, 0, 0, \
> OPNUM, TYPE); \
> goto WIN; \
> }
>
> Im struggling with this part. however, the POINTER class is an advantageous
> in the first reloading the address from memory
> - where we would not want to waste BASE POINTER and also create overlap
> problem.
Yes.
> The implication of using this code is that without it we cannot catch the
> inner reload POINTER oppertunity if we leave reload to decompose
> BASE+offset. I think this is correct :-(
>
>
> \
> push_reload (XEXP (X, 0), NULL_RTX, &XEXP (X, 0), NULL, \
> BASE_POINTER_REGS, GET_MODE (X), VOIDmode, 0, 0, \
> OPNUM, TYPE); \
> goto WIN;
>
> This part is duplicating reload and should not be here (I have patch pending
> with maintainer that removes this - for different bug)
>
> \
> } \
> else if (! (frame_pointer_needed && XEXP (X,0) == frame_pointer_rtx)) \
> { \
> push_reload (X, NULL_RTX, &X, NULL, \
> POINTER_REGS, GET_MODE (X), VOIDmode, 0, 0, \
> OPNUM, TYPE); \
> goto WIN; \
> } \
> } \
>
> This case is where offset is out of range
and we must reload not-the-frame_pointer.
The frame_pointer can be handled by reload more optimal because we have
Z register (Z+offset).
> - so we allow POINTER class on the
> basis that this is no worse than BASE POINTER. However, we leave
> frame_pointer to reload.
Because reload-pass can reload frame_pointer+big_offset because we have
anower one pointer+offser register (Z+offset).
Denis.
