Re: [avr-gcc-list] error with optimized boolean logic in gcc

[Georg-Johann Lay]

Sean D'Epagnier schrieb:
> I have had some issues compiling source code with the latest gcc in svn.
>
> The following program fails me:
>
> #include <avr/io.h>
>
> int main(void) {
>      DDRB |= _BV(DDB5);
> }
>
> avr-gcc -mmcu=at90usb1287 -c test.c -o test.o -O2
> /tmp/ccqKOBv9.s: Assembler messages:
> /tmp/ccqKOBv9.s:16: Error: number must be positive and less than 32
> make: *** [all] Error 1
>
> The assembly produced for main:
> .global main
>         .type   main, @function
> main:
> /* prologue: function */
> /* frame size = 0 */
> /* stack size = 0 */
> .L__stack_usage = 0
>         sbi 36,5
>         ret
>         .size   main, .-main
>         .ident  "GCC: (GNU) 4.7.0 20111123 (experimental)"
>
> The sbi instruction needs values 0-31, 36 is too high.
>
> The instruction in avr.md which generates this is *sbi, only
> enabled with optimizations.  I think this is a new optimization
> added, but 0x20 needs to be subtracted from the memory location.
>
> In avr.md I changed:
>     return "sbi %i0,%2";
> to
>     return "sbi %i0-0x20,%2";
>
> It fixed the problem.  I think this needs to be done all over the place

This is an incorrect fix, the problem must be somewhere else.

%i shall subtract avr_current_arch->sfr_offset which is 0x20 for all 
architectures.  The reason to use %i and not %m is to avoid magic 
numbers 0x20 all over the place, see top of following changeset and %i 
implementation in avr.c:print_operand()

http://gcc.gnu.org/viewcvs?view=revision&revision=181552

+      else if (code == 'i')
+        {
+          if (!io_address_operand (addr, GET_MODE (x)))
+            fatal_insn ("bad address, not an I/O address:", addr);
+
+          switch (INTVAL (addr))
+            {
+            case RAMPZ_ADDR: fprintf (file, "__RAMPZ__"); break;
+            case SREG_ADDR: fprintf (file, "__SREG__"); break;
+            case SP_ADDR:   fprintf (file, "__SP_L__"); break;
+            case SP_ADDR+1: fprintf (file, "__SP_H__"); break;
+
+            default:
+              fprintf (file, HOST_WIDE_INT_PRINT_HEX,
+                       UINTVAL (addr) - avr_current_arch->sfr_offset);
+              break;
+            }
+        }

> for sbi and cbi, as well as for in and out.  There might be a better
> way to more elegantly output the subtracted value so the assembler doesn't
> need to do the subtraction.  Does anyone know who made the changes?
>
> I am using the latest version in svn.
>
> Sean

Johann