[Bug c/36804] New: For-loop never exits in gcc for ARM.

[Bug c/36804] New: For-loop never exits in gcc for ARM.

[dan dot aberg at keystream dot se]

I've made a small example where a for-loop never exits when it should. I have
tried gcc 4.2.1, 4.2.4 and 4.3.1 with the same result. Gcc 4.1.1 works.

GCC is configured with:
../configure --prefix=/opt/arm-linux/arm --host=i686-linux-gnu
--target=arm-linux-gnu  --build=i686-linux-gnu
--includedir=/opt/arm-linux/arm/arm-linux-gnu/usr/include --enable-multilib
--enable-threads --disable-nls --enable-shared --enable-languages=c,c++
--enable-__cxa_atexit --enable-c99 --enable-long-long

The example is compiled with:
arm-linux-gnu-gcc -O1 -Wall -march=armv5 -o bug main.c

main.c:
---
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

struct dummy {
        unsigned short count;
        unsigned short options;
};

unsigned foo (unsigned x)
{
        return x << 1;
}

int main (int argc, char* argv[])
{
        struct dummy *d;
        unsigned count;
        unsigned i;
        unsigned short* w;
        unsigned phase;
        unsigned long long val;

        d          = malloc (sizeof(struct dummy));
        d->count   = 1;
        d->options = 0;
        count      = d->count;
        w          = malloc (sizeof(unsigned short));

        for (i=0; i<count; i++) {
                phase = (unsigned)((long long)(0xFFFFFFFF) * i / count);
                val   = foo (phase);
                w[i]  = (unsigned short)val;
                fprintf (stderr, "i: %u, count: %u\n", i, count);
        }

        return 0;
}
---


-- 
           Summary: For-loop never exits in gcc for ARM.
           Product: gcc
           Version: 4.2.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dan dot aberg at keystream dot se
 GCC build triplet: i686-linux-gnu
  GCC host triplet: i686-linux-gnu
GCC target triplet: arm-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36804

[Bug target/36804] For-loop never exits in gcc for ARM.

[rearnsha at gcc dot gnu dot org]

------- Comment #1 from rearnsha at gcc dot gnu dot org  2008-12-16 16:45 -------
I'm unable to reproduce this with any of svn-trunk, gcc-4.1.3 (debian),
gcc-4.3.3 (SVN) or gcc-4.3.2 (debian).  The loop essentially reads as

  mov  r7, #1
  mov  r6, #0
L5:
  ...
  add  r6, r6, #1
  cmp  r7, r6
  bhi  L5

This will iterate only while r7 is larger than r6 -- that is, exactly once,
when r6 is 0.


-- 

rearnsha at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |WORKSFORME


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36804