[Bug c/38644] New: Optimization flag -O1 -fschedule-insns2 causes wrong code

[davejmurphy at me dot com]

The -fschedule-insns2 optimisation causes wrong code to be emitted for the
following testcase. The assembly code loads a value from a stack frame which
has already been deallocated.

This is similar to http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30282 for
powerpc-eabi.

extern int doStreamReadBlock(int *, char *, int size, int);

char readStream(int *s)
{
    char c = 0;
    doStreamReadBlock(s, &c, 1, *s);
    return c;
}

arm-eabi davem$ arm-eabi-gcc -v -O2 -mthumb -c test.c 
Using built-in specs.
Target: arm-eabi
Configured with: ../../gcc-4.3.2/configure --enable-languages=c,c++
--with-cpu=arm7tdmi --enable-interwork --enable-multilib --with-gcc
--with-gnu-ld --with-gnu-as --disable-shared --disable-threads
--disable-win32-registry --disable-nls --disable-debug --disable-libmudflap
--disable-libssp --disable-libgomp --disable-libstdcxx-pch --target=arm-eabi
--with-newlib --prefix=/opt/devkitpro/devkitARM
--with-bugurl=http://wiki.devkitpro.org/index.php/Bug_Reports
--with-pkgversion='devkitARM release 24'
Thread model: single
gcc version 4.3.2 (devkitARM release 24) 

00000000 <readStream>:
   0:   b510            push    {r4, lr}
   2:   b082            sub     sp, #8
   4:   466c            mov     r4, sp
   6:   3407            adds    r4, #7
   8:   2300            movs    r3, #0
   a:   7023            strb    r3, [r4, #0]
   c:   1c21            adds    r1, r4, #0
   e:   6803            ldr     r3, [r0, #0]
  10:   2201            movs    r2, #1
  12:   f7ff fffe       bl      0 <doStreamReadBlock>
  16:   b002            add     sp, #8          <--- stack frame deallocated
  18:   7820            ldrb    r0, [r4, #0]    <--- value loaded from stack
frame
  1a:   bc10            pop     {r4}
  1c:   bc02            pop     {r1}
  1e:   4708            bx      r1

The same thing happens with mainline

 /opt/devkitpro/devkitARM_mainline/bin/arm-eabi-gcc -v -O2 -mthumb -c test.c 
Using built-in specs.
Target: arm-eabi
Configured with: ../../../gcc_mainline/configure --disable-nls
--target=arm-eabi --prefix=/opt/devkitPro/devkitARM --enable-languages=c,c++
--with-cpu=arm7tdmi --enable-interwork --enable-multilib --with-gcc
--with-gnu-ld --with-gnu-as --disable-shared --disable-threads
--disable-win32-registry --disable-nls --disable-debug --disable-libmudflap
--disable-libssp --disable-libgomp --disable-libstdcxx-pch
Thread model: single
gcc version 4.4.0 20081223 (experimental) (GCC) 

00000000 <readStream>:
   0:   b510            push    {r4, lr}
   2:   b082            sub     sp, #8
   4:   466c            mov     r4, sp
   6:   3407            adds    r4, #7
   8:   2300            movs    r3, #0
   a:   7023            strb    r3, [r4, #0]
   c:   1c21            adds    r1, r4, #0
   e:   6803            ldr     r3, [r0, #0]
  10:   2201            movs    r2, #1
  12:   f7ff fffe       bl      0 <doStreamReadBlock>
  16:   b002            add     sp, #8
  18:   7820            ldrb    r0, [r4, #0]
  1a:   bc10            pop     {r4}
  1c:   bc02            pop     {r1}
  1e:   4708            bx      r1


-- 
           Summary: Optimization flag -O1 -fschedule-insns2 causes wrong
                    code
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: davejmurphy at me dot com
 GCC build triplet: i386-apple-darwin9.6.0
  GCC host triplet: i386-apple-darwin9.6.0
GCC target triplet: arm-none-eabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38644