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* [Bug c/18616] New: Strange optimization issue
@ 2004-11-22 23:27 manus at eiffel dot com
  2004-11-22 23:31 ` [Bug rtl-optimization/18616] " pinskia at gcc dot gnu dot org
                   ` (7 more replies)
  0 siblings, 8 replies; 9+ messages in thread
From: manus at eiffel dot com @ 2004-11-22 23:27 UTC (permalink / raw)
  To: gcc-bugs

I have an optimization bug with gcc 3.4.3 on AMD64. If I use either O1, O2 or 
O3 then it fails. Only O0 works fine. I found a small workaround which works 
for any optimization level, it suffices to add a call to printf("..") for a 
particular local variable but of course this is not acceptable. I'm not in a 
position to test if it is a AMD64 specific problem or not.

Here is the output regarding the command line I'm using:

gcc -v -g -c -O3 -Wall -pedantic -std=gnu99 -pipe -fPIC -c my_file.c
Reading specs from /usr/lib/gcc/x86_64-redhat-linux/3.4.2/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --
infodir=/usr/share/info --enable-shared --enable-threads=posix --disable-
checking --with-system-zlib --enable-__cxa_atexit --disable-libunwind-
exceptions --enable-languages=c,c++,objc,java,f77 --enable-java-awt=gtk --
host=x86_64-redhat-linux
Thread model: posix
gcc version 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)
 /usr/libexec/gcc/x86_64-redhat-linux/3.4.2/cc1 -quiet -v my_file.c -quiet -
dumpbase my_file.c -mtune=k8 -auxbase my_file -g -O3 -Wall -pedantic -
std=gnu99 -version -fPIC -o - |
 as -V -Qy -o my_file.o -
ignoring nonexistent directory "/usr/lib/gcc/x86_64-redhat-
linux/3.4.2/../../../../x86_64-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/gcc/x86_64-redhat-linux/3.4.2/include
 /usr/include
End of search list.
GNU C version 3.4.2 20041017 (Red Hat 3.4.2-6.fc3) (x86_64-redhat-linux)
        compiled by GNU C version 3.4.2 20041017 (Red Hat 3.4.2-6.fc3).
GGC heuristics: --param ggc-min-expand=98 --param ggc-min-heapsize=128172
GNU assembler version 2.15.92.0.2 (x86_64-redhat-linux) using BFD version 
2.15.92.0.2 20040927

I've attached below the .s output of an extract of the routine which fails 
(i.e. without printf):

.globl buggy_feature
    .type   buggy_feature, @function
buggy_feature:
.LFB114:
    pushq   %r12
.LCFI94:
    movl    $1, %esi
    pushq   %rbp
.LCFI95:
    pushq   %rbx
.LCFI96:
    movl    %edi, %ebx
    subq    $32, %rsp
.LCFI97:
    leaq    30(%rsp), %rdi
    call    read_int16@PLT
    movswl  30(%rsp),%edi
    xorl    %edx, %edx
    xorl    %esi, %esi
    incl    %edi
    movslq  %edi,%rdi
    call    eif_rt_xmalloc@PLT
    testq   %rax, %rax
    movq    %rax, %rbp
    je  .L1012
.L985:
    movswq  30(%rsp),%rsi
    movq    %rbp, %rdi
    call    read_char@PLT
    movswq  30(%rsp),%rdx
    movq    rt_kind_version@GOTPCREL(%rip), %rax
    movb    $0, (%rdx,%rbp)
    cmpb    $13, (%rax)
    jg  .L1013
    movl    $0, 24(%rsp)
.L987:
    leaq    22(%rsp), %rdi
    movl    $1, %esi
    call    read_int16@PLT
    leaq    20(%rsp), %rdi
    movl    $1, %esi
    call    read_int16@PLT
    movq    type_array(%rip), %rcx
    movswq  22(%rsp),%r11
    movslq  %ebx,%r9
    leaq    (%r9,%r9,4), %r8
    movq    (%rcx), %r10
    movq    8(%rcx), %rsi
    movw    %bx, (%r10,%r11,2)
    leaq    (%rsi,%r8,8), %rbx
    cmpw    $-2, 28(%rbx)
    jne .L1014


Now the same code with an additional call to printf:

.globl buggy_feature
    .type   buggy_feature, @function
buggy_feature:
.LFB114:
    pushq   %r12
.LCFI94:
    movl    %edi, %r12d
    movl    $1, %esi
    pushq   %rbp
.LCFI95:
    pushq   %rbx
.LCFI96:
    subq    $32, %rsp
.LCFI97:
    leaq    30(%rsp), %rdi
    call    read_int16@PLT
    movswl  30(%rsp),%edi
    xorl    %edx, %edx
    xorl    %esi, %esi
    incl    %edi
    movslq  %edi,%rdi
    call    eif_rt_xmalloc@PLT
    testq   %rax, %rax
    movq    %rax, %rbp
    je  .L1012
.L985:
    movswq  30(%rsp),%rsi
    movq    %rbp, %rdi
    call    read_char@PLT
    movswq  30(%rsp),%rdx
    movq    rt_kind_version@GOTPCREL(%rip), %rax
    movb    $0, (%rdx,%rbp)
    cmpb    $13, (%rax)
    jg  .L1013
    movl    $0, 24(%rsp)
.L987:
    leaq    22(%rsp), %rdi
    movl    $1, %esi
    movslq  %r12d,%rbx
    call    read_int16@PLT
    leaq    20(%rsp), %rdi
    movl    $1, %esi
    call    read_int16@PLT
    movq    type_array(%rip), %rcx
    movswq  22(%rsp),%r10
    leaq    (%rbx,%rbx,4), %r8
    leaq    .LC31(%rip), %rdi
    xorl    %eax, %eax
    movq    8(%rcx), %rsi
    movq    (%rcx), %r9
    leaq    (%rsi,%r8,8), %rbx
    movw    %r12w, (%r9,%r10,2)
    movl    %r12d, %esi
    call    printf@PLT
    cmpw    $-2, 28(%rbx)
    jne .L1014

In both cases .L1014 is defined as:

.L1014:
    xorl    %edi, %edi
    call    exit@PLT


The actual C code of the `buggy_feature' routine is:

rt_public void buggy_feature (int type_index)
{
    char *a_name;
    type_descriptor *a_conv;
    int16 nb_gen, num_attrib, name_length, dtype;
    int32 flags;

    read_int16 (&name_length, 1);
    a_name = (char *) eif_rt_xmalloc (name_length + 1, C_T, GC_OFF);
    if (a_name == NULL)
        xraise (EN_MEM);
    read_char (a_name, name_length);
    a_name[name_length] = '\0';
	if (rt_kind_version >= 0x0E) {
    	read_int32 (&flags, 1);
	} else {
		flags = 0;
	}
    read_int16 (&dtype, 1);
    read_int16 (&nb_gen, 1);

    type_array->type_index[dtype] = type_index;
    a_conv = type_array->descriptions + type_index;
// Uncomment this line to ensure the condition below is not satisfied.
//  printf ("%d\n", type_index);
    if (!((a_conv->new_type == TYPE_UNDEFINED))) {
        exit(0);
    }
}


If you comment the `printf' line then the code calls `exit (0)',
if you uncomment it, then it does not call it.

It looks to me that the value of the `rbx' register is incorrect when
there is no `printf' statement.

Let me know if you need more information.
Thanks,
Manu

-- 
           Summary: Strange optimization issue
           Product: gcc
           Version: 3.4.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: manus at eiffel dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: Linux madrid.ise 2.6.9-1.667 #1 Tue Nov 2 14:50:10 EST
                    2004 x86_


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18616


^ permalink raw reply	[flat|nested] 9+ messages in thread
end of thread, other threads:[~2004-11-30  1:38 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2004-11-22 23:27 [Bug c/18616] New: Strange optimization issue manus at eiffel dot com
2004-11-22 23:31 ` [Bug rtl-optimization/18616] " pinskia at gcc dot gnu dot org
2004-11-22 23:37 ` schwab at suse dot de
2004-11-23  0:01 ` manus at eiffel dot com
2004-11-23  0:39 ` falk at debian dot org
2004-11-23  1:17 ` manus at eiffel dot com
2004-11-23  1:53 ` giovannibajo at libero dot it
2004-11-23  2:15 ` manus at eiffel dot com
2004-11-30  1:38 ` manus at eiffel dot com

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