-fcompare-elim bug report

["Dimitar Jekov" <jimmy at ncp dot infonet dot bg>]

#!/bin/sh
tar xvfy bash-2.04.tar.bz2
cd bash-2.04
export CFLAGS="-O2 -pipe -fcompare-elim"
export LDFLAGS="-s"
./configure --enable-shared --disable-static --disable-nls i586-pc-linux-gnu
make
cd builtins
./mkbuiltins -D . shift.def
gcc -I. -I.. -I../include -I../lib -v -o shift.i -E shift.c >& CCCP
gcc -O2 -pipe -fno-compare-elim -v -o no-compare-elim.s -S shift.i >&
NO-ELIM
gcc -O2 -pipe -fcompare-elim -v -o compare-elim.s -S shift.i >& ELIM


system type: i586-pc-linux-gnu
compiler version: gcc version pgcc-2.95.2 19991024 (release)
attachment: shift.i, CCCP, no-compare-elim.s, NO-ELIM, compare-elim.s, ELIM


diff --side --width=78 no-compare-elim.s compare-elim.s produces:

<cut>
.L12:                                   .L12:
        movl $1,%edx                  |         movl $-8,%edx
        leal -1(%esi),%edi            |         leal -1(%edi),%ebp
        movl $dollar_vars,%ebx        |         movl $dollar_vars,%esi
        movl $8,%ecx                  |         movl $8,%ebx
                                      >         movl $4,%ecx
        .p2align 3                              .p2align 3
.L16:                                   .L16:
        movl (%ecx,%ebx),%eax         |         movl (%ebx,%esi),%eax
        movl %eax,(%ebx,%edx,4)       |         movl %eax,(%ecx,%esi)
        addl $4,%ecx                  |         addl $4,%ebx
        incl %edx                     |         addl $40,%ecx
        cmpl $8,%edx                  |         addl $10,%edx
        jle .L16                      |         jne .L16
<cut>

As you can see, shift.def:80 (shift.i:9500)

for (count = 1; count < 9; count++)

with -fcompare-elim assembles to something like

for (count = -8; count; count += 10)

At least, it works that way (I checked it out with gdb).
Starts with a count of -8, continues with 2, then with 12 etc. until
a Segmentation fault for 7072 (your mileage will vary) at shift.def:81

dollar_vars[count] = dollar_vars[count + 1]

Something to do with the fact that 1 - 9 == -8 and 1 + 9 == 10?

E-gards: Jimmy

attachment.tar.bz2