AVR Freaks

Magister wrote:

with 4.7.1 prerelease from 20120322 : 15468 bytes
with 4.7.1 prerelease from 20120606 : 15674 bytes

It's likely because of PR53595.

Just uploaded a new avr-gcc-4.7.1-rc1-mingw32.zip stamped 2012-06-07 with a tentative fix for that PR

Some lines above you wrote that you use pgm_read_byte_far. Consulting avr/progmem.h from AVR-LibC tells that it expands to inline assembler that uses constraint "p".

Using "p" is wrong, wrong, wrong!

AVR-LibC: SVN trunk 2294: include/avr/pgmspace.h:1030

#include 
#include 
#include 


register unsigned char __attribute__((used)) _r2 asm("r2");
register unsigned char __attribute__((used)) _r3 asm("r3");
register unsigned char __attribute__((used)) _r4 asm("r4");
register unsigned char __attribute__((used)) _r5 asm("r5");




#define GETItem(p)  (pgm_read_byte_far(pgm_read_word_far((p))))



#define AND &
#define ANL &&
#define SHR >>



  void foo(uint16_t p, uint16_t mask, int16_t p3, uint8_t p4) {

    int16_t a1;
    int16_t a2;
    struct __attribute__((__packed__)) {
      int16_t a3;
      uint8_t a4;
    } buf;


    if ((mask AND (mask-1)) == 0) {
      foo1( foo2(a1) , p3, GETItem(a1), (uint16_t *)pgm_read_word_far(a1));
    } else {

      if (!p4) {
        a1 = p3 - foo3((uint16_t *)pgm_read_word_far(a1));
      } else {
        a1 = 0; //
      }
      p += 1234;

      while (mask != 0) {
        uint16_t pp;

        pp = pgm_read_word_far(p);
        if (pp == 0xFFFF) {
          mask = 0;
        } else if (pp != 0) {
          uint16_t a5;
          uint8_t a6;

          a5 = pgm_read_word_far(pp);
          a6 = foo2(pp);

          if (((mask AND 0x01) != 0) ANL (a6 != 0)) {

            if (p3 == 0x7FFF) {
              buf.a3 = p3;
              buf.a4 = 0;
            } else {

              if (!p4) {
                buf.a3 = foo3((uint16_t *)a5) + a1;
              } else {
                buf.a3 = p3 + a2 - pgm_read_word_far(pp);
              }

              buf.a4 = GETItem(pp);
            }

            foo1(a6, buf.a3, buf.a4, (uint16_t *)a5);
          }

        }
        mask = mask SHR 1;
        p = p + 1234;
      }
    }
  }

c:\tmp>"c:\PROGRA~1\Atmel\AVRTools\Wavr-gcc-4.7.1-rc1-ming
w32\bin\avr-gcc" w.c -c -o w.o -mmcu=atmega2561 -Os -mstrict-X
w.c: In function 'foo':
w.c:55:16: error: can't find a register in class 'BASE_POINTER_REGS' while reloa
ding 'asm'
w.c:55:16: error: 'asm' operand has impossible constraints

c:\tmp>"c:\PROGRA~1\Atmel\AVRTools\Wavr-gcc-4.7.1-rc1-ming
w32\bin\avr-gcc" w.c -c -o w.o -mmcu=atmega2561 -Os

c:\tmp>"c:\PROGRA~1\Atmel\AVRTools\Wavr-gcc-4.7.1-rc1-ming
w32\bin\avr-gcc" w.c -c -o w.o -mmcu=atmega2561 -O3 -mstrict-X
w.c: In function 'foo':
w.c:55:16: error: can't find a register in class 'BASE_POINTER_REGS' while reloa
ding 'asm'
w.c:55:16: error: 'asm' operand has impossible constraints

c:\tmp>"c:\PROGRA~1\Atmel\AVRTools\Wavr-gcc-4.7.1-rc1-ming
w32\bin\avr-gcc" w.c -c -o w.o -mmcu=atmega2561 -O2 -mstrict-X
w.c: In function 'foo':
w.c:55:16: error: can't find a register in class 'BASE_POINTER_REGS' while reloa
ding 'asm'
w.c:55:16: error: 'asm' operand has impossible constraints

c:\tmp>"c:\PROGRA~1\Atmel\AVRTools\Wavr-gcc-4.7.1-rc1-ming
w32\bin\avr-gcc" w.c -c -o w.o -mmcu=atmega2561 -O1 -mstrict-X

c:\tmp>"c:\PROGRA~1\Atmel\AVRTools\Wavr-gcc-4.7.1-rc1-ming
w32\bin\avr-gcc" w.c -c -o w.o -mmcu=atmega2561 -O0 -mstrict-X

c:\tmp>

avr-size -C --mcu=atxmega128a1 main.elf
AVR Memory Usage
----------------
Device: atxmega128a1

Program:   79544 bytes (57.1% Full)
(.text + .data + .bootloader)

Data:       6974 bytes (85.1% Full)
(.data + .bss + .noinit)

avr-size -C --mcu=atxmega128a1 main.elf
AVR Memory Usage
----------------
Device: atxmega128a1

Program:   73598 bytes (52.8% Full)
(.text + .data + .bootloader)

Data:       6664 bytes (81.3% Full)
(.data + .bss + .noinit)

The avr-gcc 4.7.1 is released officialy!!!

...
Compiling C: main.c
avr-gcc -c -mmcu=atmega1281 -I. -gdwarf-2 -DF_CPU=14745600UL -Os -pedantic -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -fno-split-wide-types -flto -ffunction-sections -fdata-sections -Wl,--relax  -fno-tree-scev-cprop -finline-small-functions -fearly-inlining -Wa,-adhlns=../obj/main.lst -std=c99 -MMD -MP -MF ../obj/dep/main.o.d main.c -o ../obj/main.o 

Linking: ../bin/Paragraph5/Paragraph_PID.elf
avr-gcc -mmcu=atmega1281 -I. -gdwarf-2 -DF_CPU=14745600UL -Os -pedantic -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -fno-split-wide-types -flto -ffunction-sections -fdata-sections -Wl,--relax  -fno-tree-scev-cprop -finline-small-functions -fearly-inlining -Wa,-adhlns=../obj/spi.o -MMD -MP -MF ../obj/dep/Paragraph_PID.elf.d ../obj/spi.o ../obj/rtc_ds1390.o ../obj/rtc.o ../obj/rtc_str.o ../obj/df.o ../obj/ks108.o ../obj/lcd128x64.o ../obj/str_ascii.o ../obj/str_ml.o ../obj/lcd_str.o ../obj/lcd_str_ml.o ../obj/lcd_str_rtc.o ../obj/lcd_img.o ../obj/lcd_gfx.o ../obj/keys.o ../obj/di.o ../obj/led_keyboard.o ../obj/led7.o ../obj/crc16.o ../obj/bin_bcd.o ../obj/filter.o ../obj/gui_progress_bar.o ../obj/gui_scroll_bar.o ../obj/plot_misc.o ../obj/plot_series.o ../obj/plot_background.o ../obj/plot.o ../obj/plot_scroll.o ../obj/plot_zoom.o ../obj/plot_arch.o ../obj/plot_main.o ../obj/menu_content_items_callback.o ../obj/menu_items_rules.o ../obj/menu_items_access.o ../obj/menu_item.o ../obj/menu_item_int.o ../obj/menu_item_enum.o ../obj/menu_item_cmd.o ../obj/menu_item_rtc.o ../obj/menu_item_float.o ../obj/menu_item_submenu.o ../obj/menu_xls.o ../obj/menu_std.o ../obj/menu_plot.o ../obj/menu_arch.o ../obj/menu.o ../obj/rs485.o ../obj/modbus_buffer.o ../obj/modbus_timer.o ../obj/modbus_slave_func.o ../obj/modbus_slave.o ../obj/ad7792.o ../obj/max6627.o ../obj/adc.o ../obj/dac.o ../obj/nsc.o ../obj/ain_cj.o ../obj/ain_tc.o ../obj/ain_rtd.o ../obj/ain_unified.o ../obj/ain_logical.o ../obj/ain_demo.o ../obj/ain.o ../obj/dffs_page.o ../obj/dffs_volume.o ../obj/dffs_info.o ../obj/dffs.o ../obj/timers.o ../obj/gui_base.o ../obj/init_port.o ../obj/init_dev.o ../obj/errors.o ../obj/psychrometer.o ../obj/mathematics.o ../obj/led_misc.o ../obj/relay.o ../obj/pid_timer.o ../obj/pid.o ../obj/registrator.o ../obj/main.o --output ../bin/Paragraph5/Paragraph_PID.elf  -Wl,--gc-section   -Wl,-u,vfprintf -lprintf_flt  -lm

z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(ceil.o):../../../../../source/avr-libc-1.8/libm/fplib/ceil.S:57:(.text.avr-libc.fplib+0xc): relocation truncated to fit: R_AVR_13_PCREL against symbol `__fp_szero' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fp_zero.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(exp.o):../../../../../source/avr-libc-1.8/libm/fplib/exp.S:53:(.text.avr-libc.fplib+0x4): relocation truncated to fit: R_AVR_13_PCREL against symbol `__fp_inf' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fp_inf.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(exp.o):../../../../../source/avr-libc-1.8/libm/fplib/exp.S:54:(.text.avr-libc.fplib+0x6): relocation truncated to fit: R_AVR_13_PCREL against symbol `__fp_zero' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fp_zero.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(exp.o):../../../../../source/avr-libc-1.8/libm/fplib/exp.S:55:(.text.avr-libc.fplib+0x8): relocation truncated to fit: R_AVR_13_PCREL against symbol `__fp_nan' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fp_nan.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(exp.o):../../../../../source/avr-libc-1.8/libm/fplib/exp.S:59:(.text.avr-libc.fplib+0xa): relocation truncated to fit: R_AVR_13_PCREL against symbol `__fp_splitA' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fp_split3.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(exp.o):../../../../../source/avr-libc-1.8/libm/fplib/exp.S:72:(.text.avr-libc.fplib+0x20): relocation truncated to fit: R_AVR_13_PCREL against symbol `__mulsf3_pse' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(mulsf3x.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(floor.o):../../../../../source/avr-libc-1.8/libm/fplib/floor.S:56:(.text.avr-libc.fplib+0xc): relocation truncated to fit: R_AVR_13_PCREL against symbol `__fp_szero' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fp_zero.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fma.o):../../../../../source/avr-libc-1.8/libm/fplib/fma.S:48:(.text.avr-libc.fplib+0x0): relocation truncated to fit: R_AVR_13_PCREL against symbol `__mulsf3x' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(mulsf3x.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fma.o):../../../../../source/avr-libc-1.8/libm/fplib/fma.S:53:(.text.avr-libc.fplib+0xa): relocation truncated to fit: R_AVR_13_PCREL against symbol `__fp_round' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fp_round.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fp_powser.o):../../../../../source/avr-libc-1.8/libm/fplib/fp_powser.S:79:(.text.avr-libc.fplib+0x1a): relocation truncated to fit: R_AVR_13_PCREL against symbol `__mulsf3x' defined in .text.avr-libc.fplib section in z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(mulsf3x.o)
z:/gcc/avr-gcc/bin/../lib/gcc/avr/4.7.1/../../../../avr/lib/avr51\libc.a(fp_rempio2.o):../../../../../source/avr-libc-1.8/libm/fplib/fp_rempio2.S:50:(.text.avr-libc.fplib+0x0): additional relocation overflows omitted from the output
collect2.exe: error: ld returned 1 exit status
make: *** [../bin/Paragraph5/Paragraph_PID.elf] Error 1

What means "W/O"?

-combine and -fwhole-program are noe more needed since LTO which is even more powerful.

Another (simpler) way to enable link-time optimization is:
gcc -o myprog -flto -O2 foo.c bar.c

CFLAGS += -std=gnu99
CFLAGS += -Os
CFLAGS += -pedantic
CFLAGS += -Wall
CFLAGS += -Wextra

void func(void)
{
	static const int PROGMEM x = 0;
	(void)x; // dummy
}

static const int PROGMEM x = 0;

void func(void)
{
	(void)x; // dummy
}