Re: [avr-gcc-list] Bug35013 - Incomplete check for pm() annotation

[Andy H]

Note that this bug is also related to:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27192

which has similar issue generating "byte address" instead of word 
address. Oddly my patch appears to fix  that without problem, using :

 45 0014 80E0              ldi r24,lo8(pm(foo+512))
 46 0016 90E0              ldi r25,hi8(pm(foo+512))
 47 0018 9093 0000         sts (q)+1,r25
 48 001c 8093 0000         sts q,r24


So it would appear problem with pm(foo+1) is more complicated than it 
appears.

Ideas?




Andrew Hutchinson wrote:
> I have looked at fix for the function pointer arithmetic bug :
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35013
>
> This is due to avr-gcc not  recognizing an address of  the form  foo+k 
> as a program memory location. So a table of address for foo, foo()+1 
> and foo()+2 ends up as:
>
>  46 0006 0000              .word    pm(foo)
>  47 0008 0000              .word    foo+1
>  48 000a 0000              .word    foo+2
>
>
> The patch I created now correctly treats addresses of the form address 
> + constant as program memory addresses.
>
>  79 0006 0000              .word    pm(foo)
>  80 0008 0000              .word    pm(foo+1)
>  81 000a 0000              .word    pm(foo+2)
>
> However, the assembler does not seem to cope with the resultant 
> expressions pm(address+k) and gives me error:
> pmaddr.o:(.data+0x8): warning: internal error: out of range error
>
> How do I get around this?
>
>
> Andy
>
>
>
> Andrew Hutchinson wrote:
> > There is a bug!
> >
> > Backend (avr part) creates special "pm()" annotation by looking at 
> > RTL. This is done in avr.c by this function:
> >
> > static bool
> > avr_assemble_integer (rtx x, unsigned int size, int aligned_p)
> > {
> > debug_rtx(x); /*ADDED TO DEBUG*/
> > fprintf(stderr,"size=%d align=%d\n\n",size,aligned_p); /*ADDED TO 
> > DEBUG*/
> >  if (size == POINTER_SIZE / BITS_PER_UNIT && aligned_p
> >      && ((GET_CODE (x) == SYMBOL_REF && SYMBOL_REF_FUNCTION_P (x))
> >      || GET_CODE (x) == LABEL_REF))
> >    {
> >      fputs ("\t.word\tpm(", asm_out_file);
> >      output_addr_const (asm_out_file, x);
> >      fputs (")\n", asm_out_file);
> >      return true;
> >    }
> >  return default_assemble_integer (x, size, aligned_p);
> > }
> >
> > (I added 2 lines to debug it)
> >
> > You will see it looks symbol_ref or label_ref - otherwise it does not 
> > use pm.
> >
> > So I ran it with following testcase to see what argument get sent:
> >
> > //Dummy func
> > int table[]= {1,2};
> > char ctable[]= {3,4};
> > void foo(void) {}
> >  
> > //Table with address manipulation
> > void (* const pFuncTable[]) (void) = {
> >   foo + 0,
> >   (foo + 1),
> >   foo +2
> > };
> >
> > ....and we get the following:
> >
> > (const_int 1 [0x1])
> > size=2 align=1
> >
> > (const_int 2 [0x2])
> > size=2 align=1
> >
> > (const_int 3 [0x3])
> > size=1 align=1
> >
> > (const_int 4 [0x4])
> > size=1 align=1
> >
> > (symbol_ref:HI ("foo") [flags 0x3] <function_decl 0x7fdcf030 foo>)
> > size=2 align=1
> >
> > (const:HI (plus:HI (symbol_ref:HI ("foo") [flags 0x3] <function_decl 
> > 0x7fdcf030 foo>)
> >        (const_int 1 [0x1])))
> > size=2 align=1
> >
> > (const:HI (plus:HI (symbol_ref:HI ("foo") [flags 0x3] <function_decl 
> > 0x7fdcf030 foo>)
> >        (const_int 2 [0x2])))
> > size=2 align=1
> >
> > You will see last two cases are an expression with outer code as 
> > const:HI so it will not match, it does not add pm().
> >
> > Please report as bug. Other may suggest the correct way of fixing 
> > this. I am not sure why the test is so specific.
> >
> > Andy
>
>
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