Re: An even smaller test case. Cast to int of char, and not...;

[Steven Bosscher <s dot bosscher at student dot tudelft dot nl>]

Op di 11-03-2003, om 14:32 schreef Diego Novillo:
> On Mon, 2003-03-10 at 18:20, Steven Bosscher wrote:
> 
> > This is a piece of libiberty/cplus-dem.c:demangle_prefix().  The inlined
> > strspn() causes an ICE, and hence a bootstrap failure, on at least
> > i[56]86, todays sources.
> > 
> What are you bootstrapping with?  While I can reproduce the failure with
> this testcase, I am yet to get a bootstrap failure on P3, P4, x86-64 and
> ppc.
> 
> Thanks for the testcase.  Diego.

I'm bootstrapping on and for i586-pc-linux-gnu.
system compiler is GCC 2.95.3.
glibc is 2.2.2.

The tree-ssa sources were up-to-date when I reported, and I updated last
night again to see if Jeff's changes made some differences, but the ICE
is still there.  This was a C-only bootstrap.

The bootstrapped compiler is:
GNU C version 3.5-tree-ssa 20030302 (experimental) (i586-pc-linux-gnu)
	compiled by GNU C version 3.5-tree-ssa 20030302 (experimental).
GGC heuristics: --param ggc-min-expand=42 --param ggc-min-heapsize=23891



The optimized tree is:

;; Function bar (bar)

bar ()
{
  int T.3;
  char ch;

  T.3 = (int)ch;
  {
    const char accept;

    (void)0;
    {
      char T.1;
      char T.2;
      const char * s;

      while (1)
        {
          T.1 = *s;
          T.2 = (const char)T.1;
          if (T.2 != T.3)
            {
              goto <UL1070>;
            }
        };
      <UL1070>:;
    }
  }
}

In the test case, the ICE happens on the condition of the "while"
statement (pretty safe claim since there is no loop body in the test
case :-).
So in the optimized version, the ICE is somewhere in "if (T.2 != T.3)".


I sent you a trace already, here is what I see in gdb:

GNU gdb 5.2.1
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GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
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This GDB was configured as "i586-pc-linux-gnu"...se
tBreakpoint 1 at 0x8118756: file ../../gcc-ssa/gcc/diagnostic.c, line 1372.
Breakpoint 2 at 0x8049778
Breakpoint 3 at 0x8049558
(gdb) set args -O bug.c
(gdb) run
Starting program: /home/steven/devel/gcc/build-ssa/gcc/cc1 -O bug.c
Breakpoint 2 at 0x40056745
Breakpoint 3 at 0x40055337
 foo bar
Breakpoint 1, fancy_abort (file=0x83be833 "../../gcc-ssa/gcc/explow.c", line=731, 
    function=0x83be8f4 "copy_to_mode_reg") at ../../gcc-ssa/gcc/diagnostic.c:1372
1372	  internal_error ("in %s, at %s:%d", function, trim_filename (file), line);
(gdb) up
#1  0x0813cbc6 in copy_to_mode_reg () at ../../gcc-ssa/gcc/explow.c:731
731	    abort ();
(gdb) up
#2  0x0825ff32 in prepare_operand (icode=841, x=0x40146560, opnum=1, mode=QFmode, wider_mode=16820, 
    unsignedp=0) at ../../gcc-ssa/gcc/optabs.c:3732
3732	    x = copy_to_mode_reg (insn_data[icode].operand[opnum].mode, x);
(gdb) down
#1  0x0813cbc6 in copy_to_mode_reg () at ../../gcc-ssa/gcc/explow.c:731
731	    abort ();
(gdb) l
726	     do the computation.  */
727	  if (! general_operand (x, VOIDmode))
728	    x = force_operand (x, temp);
729	
730	  if (GET_MODE (x) != mode && GET_MODE (x) != VOIDmode)
731	    abort ();
732	  if (x != temp)
733	    emit_move_insn (temp, x);
734	  return temp;
735	}
(gdb) p debug_rtx (x)
(reg/v:SI 58 [ T.3 ])
$1 = void
(gdb) p x->mode
$2 = SImode
(gdb) p mode
$3 = QImode
(gdb) 


I don't know what to make of this, but I'm a bit confused about the
types we use...  If you cheat a bit and make the .t14.optimized dump
compilable:

void
bar (void)
{
  int _T3_;
  char ch;

  _T3_ = (int)ch;
  {
    const char accept;

    (void)0;
    {
      char _T1_;
      char _T2_;
      const char * s;

      while (1)
        {
          _T1_ = *s;
          _T2_ = (const char) _T1_;
          if (_T2_ != _T3_)
            {
              goto end;
            }
        };
      end:;
    }
  }
}


Gives you:

;; Function bar (bar)

bar ()
{
  int T.1;
  int _T3_;
  char ch;

  _T3_ = (int)ch;
  {
    const char accept;

    {
      char _T1_;
      char _T2_;
      const char * s;

      while (1)
        {
          {
            _T1_ = *s;
            (void)0;
            T.1 = (int) _T1_;
            if (T.1 != _T3_)
              {
                {
                  goto end;
                }
              }
          }
        };
      <ULdb60>:;;
      end:;
    }
  }
}

_T1_ is a char, and we cast it to "T.1 = (int) _T1_".  So in this case
we compare one int with another ("int T.1" with "int _T3_").  In the
snippet that ICEs, we compare a "const char" to an "int".  Maybe that
causes the problem?

Greetz
Steven