[Bug c/31644] New: Code snippet that fails to compile with optimization enabled

[Bug c/31644] New: Code snippet that fails to compile with optimization enabled

[dhylands at gmail dot com]

The following code snippet fails to compile with -Os -O1 -O2 or -O3. It
compiles fine using -O0

I tested both the Win32 and linux versions of the compiler and they both fail
the same way.

The exact command line used was:
avr-gcc -c -mmcu=atmega168 -Os ee-fail.c

Removing the second call to fill_pwm_table also allows the code to compile.

The error message received from the compiler are as follows:
ee-fail.c: In function 'build_pwm_table':
/home/dhylands/avr-4.1.1/lib/gcc/avr/4.1.1/../../../../avr/include/avr/eeprom.h:208:
error: can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'
/home/dhylands/avr-4.1.1/lib/gcc/avr/4.1.1/../../../../avr/include/avr/eeprom.h:208:
error: can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

avr-gcc -v on my linux box reports:
Using built-in specs.
Target: avr
Configured with: ../../source/gcc-4.1.1/configure -v --target=avr --disable-nls
--prefix=/home/dhylands/avr-4.1.1 --with-gnu-ld --with-gnu-as
--enable-languages=c,c++ --quiet --disable-libssp --with-dwarf2
Thread model: single
gcc version 4.1.1


#include <avr/eeprom.h>

uint8_t    pwm_tab_1 [126];

static uint16_t  ee_chan_1_min EEMEM = 140,
                ee_chan_1_cent EEMEM = 188,
                ee_chan_1_max EEMEM = 240,
                ee_chan_1_forw_min EEMEM = 20,
                ee_chan_1_forw_max EEMEM = 90,
                ee_chan_1_back_max EEMEM = 80;

void fill_pwm_table (int8_t chan_num, uint8_t pwm [], int16_t forward_max,
                    int16_t center, int16_t reverse_min, int16_t forward_high,
                    int16_t forward_low, int16_t reverse_high );

void build_pwm_table (void)
{
 int16_t   center_1,
           forward_max_1,
           reverse_min_1,
           forward_high_1,
           forward_low_1,
           reverse_high_1;

 center_1 = eeprom_read_word (&ee_chan_1_cent);

 forward_max_1 = eeprom_read_word (&ee_chan_1_max);
 reverse_min_1 = eeprom_read_word (&ee_chan_1_min);
 forward_high_1 = eeprom_read_word (&ee_chan_1_forw_max);
 forward_low_1 = eeprom_read_word (&ee_chan_1_forw_min);
 reverse_high_1 = eeprom_read_word (&ee_chan_1_back_max);

 fill_pwm_table (1, pwm_tab_1, forward_max_1, center_1, reverse_min_1,
                 forward_high_1, forward_low_1, reverse_high_1);

 fill_pwm_table (1, pwm_tab_1, forward_max_1, center_1, reverse_min_1,
                 forward_high_1, forward_low_1, reverse_high_1);
}


-- 
           Summary: Code snippet that fails to compile with optimization
                    enabled
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dhylands at gmail dot com
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: avr


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] Code snippet that fails to compile with optimization enabled

[j at uriah dot heep dot sax dot de]

------- Comment #1 from j at uriah dot heep dot sax dot de  2007-04-21 09:55 -------
Created an attachment (id=13400)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=13400&action=view)
Preprocessed source


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] [avr] can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

[eweddington at cso dot atmel dot com]

------- Comment #2 from eweddington at cso dot atmel dot com  2007-05-03 16:56 -------
Confirmed on GCC 4.1.2.


-- 

eweddington at cso dot atmel dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
      Known to fail|                            |4.1.1 4.1.2
   Last reconfirmed|0000-00-00 00:00:00         |2007-05-03 16:56:59
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] [avr] can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

[eweddington at cso dot atmel dot com]

------- Comment #3 from eweddington at cso dot atmel dot com  2007-05-30 19:34 -------
Testcase fails for 4.2.0 and 4.3-20070525.


-- 

eweddington at cso dot atmel dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|4.1.1 4.1.2                 |4.1.1 4.1.2 4.2.0
   Last reconfirmed|2007-05-03 16:56:59         |2007-05-30 19:34:44
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] [avr] can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

[pavel dot petrovic at gmail dot com]

------- Comment #4 from pavel dot petrovic at gmail dot com  2007-07-28 20:24 -------
This bug is quite cruel. I have similar application, also for atmega168 and
WinAVR (avr-gcc (GCC) 4.1.2 (WinAVR 20070525)), and the following lines do not
compile giving the same error. Even worse, if the code is with for-loop, it
compiles, but it crashes when the variable is accessed, or it overwrites
it with a value of a different variable (that is not very neighboring one).

  //load calibrated values from eeprom  
  left_ir_min = eeprom_read_word((uint16_t*)0);
  left_ir_center = eeprom_read_word((uint16_t*)2);
  left_ir_max = eeprom_read_word((uint16_t*)4);
  right_ir_min = eeprom_read_word((uint16_t*)6);
  right_ir_center = eeprom_read_word((uint16_t*)8);
  right_ir_max = eeprom_read_word((uint16_t*)10);

  left_rot[0] = eeprom_read_word((uint16_t*)12);
  right_rot[0] = eeprom_read_word((uint16_t*)14);
  left_rot[1] = eeprom_read_word((uint16_t*)16);
  right_rot[1] = eeprom_read_word((uint16_t*)18);
  left_rot[2] = eeprom_read_word((uint16_t*)20); 
  /* any of the following lines, if present, cause compiler to fail */
  right_rot[2] = eeprom_read_word((uint16_t*)22); 
  left_rot[3] = eeprom_read_word((uint16_t*)24); 
  right_rot[3] = eeprom_read_word((uint16_t*)26); 


-- 

pavel dot petrovic at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pavel dot petrovic at gmail
                   |                            |dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] [avr] can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

[wvangulik at xs4all dot nl]

------- Comment #5 from wvangulik at xs4all dot nl  2007-11-01 21:50 -------
It seems that this is caused by the fact that eeprom_read_word is actually a
piece of inline assembler returning it's value in the Z register, using z as
"pointer class" description.

This then somehow eliminates the compiler's ability allocate a pointer.

Here is my test file source:
compile using: -Wall, -Os -mmcu=atmega16

===========================================================
#define u16 unsigned int

//If both are defined it will not compile

#define EXTRA_VAR   //Use this to create extra variable parsing
#define USE_REG_Z   //Use this to make use of Z register

static inline u16 eeprom_read_word(u16* p)
{

#ifdef USE_REG_Z
  register u16 result asm("r30");
#else
  register u16 result asm("r24");
#endif  

  asm volatile (
  " ; Do nothing, just fake write to result"
      : "+x" (p),
         "=r" (result)
      :  );    
  return result;  

}


extern void foo(  u16 in0,
                  u16 in1, 
                  u16 in2, 
                  u16 in3, 
                  u16 in4, 
#ifdef EXTRA_VAR
                  u16 in5, 
#endif
                  u16 in6);


void bar(void) 
{
  u16 in0 = eeprom_read_word((u16*)0);
  u16 in1 = eeprom_read_word((u16*)1);
  u16 in2 = eeprom_read_word((u16*)2);
  u16 in3 = eeprom_read_word((u16*)3);
  u16 in4 = eeprom_read_word((u16*)4);
  u16 in5 = eeprom_read_word((u16*)5);
  u16 in6 = eeprom_read_word((u16*)6);

  foo(  in0,
        in1,
        in2,
        in3,
        in4,
#ifdef EXTRA_VAR
        in5, 
#endif
        in6 );

  foo(  in0,
        in1,
        in2,
        in3,
        in4,
#ifdef EXTRA_VAR
        in5, 
#endif
        in6  );  

}

When compiling you can see that adding an extra variable gives the problem. But
then changing the return variable to r24 solves the problem.

Hmm while typing I found another fishy thing:
Compiling for r24 with and without extra_var gives pushes of all registers.
However r12 is not used when compiled for non extra var. But using extra stack
instead

And trying -mcall-prologues does not invoke the prologue call when using extra
var and r24... it does for the other 2 ok compiling combinations.

I hope someone can make something out of this.

Oh and the r30 instead of z gives the following (more descriptive) error:

(insn 14 12 16 0 (set (reg/v:HI 54 [ in0 ])
        (reg/v:HI 30 r30 [ result ])) 12 {*movhi} (insn_list:REG_DEP_TRUE 12
(ni
l))
    (expr_list:REG_DEAD (reg/v:HI 30 r30 [ result ])
        (nil)))
test.c:67: confused by earlier errors, bailing out

This involves movhi* which is in other bugreports as well, maybe this is the
vital clue?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] [avr] can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

[wvangulik at xs4all dot nl]

------- Comment #6 from wvangulik at xs4all dot nl  2007-11-01 21:53 -------
(In reply to comment #5)
Oops forgot to tell I am using avr-gcc 4.1.2


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] [avr] can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

[sascha-web-gcc dot gnu dot org at silbe dot org]

------- Comment #7 from sascha-web-gcc dot gnu dot org at silbe dot org  2008-01-08 19:29 -------
Created an attachment (id=14902)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14902&action=view)
another asm code block triggering the error

Just been hit by this after upgrading to Ubuntu gutsy (avr-gcc 4.1.0). Custom
asm snippet triggering the error (does NOT use movhi) is attached. This
compiled fine previously.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] [avr] can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

[eric dot weddington at atmel dot com]

------- Comment #8 from eric dot weddington at atmel dot com  2008-01-08 19:49 -------
(In reply to comment #7)
> Created an attachment (id=14902)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14902&action=view) [edit]
> another asm code block triggering the error
> 
> Just been hit by this after upgrading to Ubuntu gutsy (avr-gcc 4.1.0). Custom
> asm snippet triggering the error (does NOT use movhi) is attached. This
> compiled fine previously.
> 

Could you post your command line for this test case? And can you please post a
pre-processed source for your test case? This case produces additional errors
other than the one described in the bug.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] [avr] can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

[aesok at gcc dot gnu dot org]

------- Comment #9 from aesok at gcc dot gnu dot org  2008-09-14 12:51 -------
Subject: Bug 31644

Author: aesok
Date: Sun Sep 14 12:50:10 2008
New Revision: 140360

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=140360
Log:
        PR target/19636
        PR target/24894
        PR target/31644
        PR target/31786
        * config/avr/avr.c (legitimate_address_p): Fix problem where subreg
        is not recognized as a valid register usage. Allow REG_X to be used
        as a base pointer.
        * config/avr/avr.h (LEGITIMIZE_RELOAD_ADDRESS): Remove code that
        forces a reload when using a base register.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/avr/avr.c
    trunk/gcc/config/avr/avr.h


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644

[Bug target/31644] [avr] can't find a register in class 'BASE_POINTER_REGS' while reloading 'asm'

[eric dot weddington at atmel dot com]

------- Comment #10 from eric dot weddington at atmel dot com  2010-01-29 17:47 -------
I have in my list this bug as fixed in 4.4.0. Closing.


-- 

eric dot weddington at atmel dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31644