Date: Tue, 28 Aug 2001 23:15:58 -0700 (PDT) From: Petr Lampa <lampa@fee.vutbr.cz> To: freebsd-gnats-submit@FreeBSD.org Subject: gnu/30181: gcc-2.95.3 -O2 optimalization bug Message-ID: <200108290615.f7T6FwW24091@freefall.freebsd.org>
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>Number: 30181
>Category: gnu
>Synopsis: gcc-2.95.3 -O2 optimalization bug
>Confidential: no
>Severity: serious
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Aug 28 23:20:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: Petr Lampa
>Release: 4.3-RELEASE,4.3-STABLE,4.4-RC1
>Organization:
Dept. of Computer Science FEECS BUT
>Environment:
FreeBSD boco.fee.vutbr.cz 4.3-STABLE FreeBSD 4.3-STABLE #1: Thu Jul 19 08:48:56 CEST 2001 lampa@boco.fee.vutbr.cz:/src/sys/sys-44/compile/BOCO i386
>Description:
gcc-2.95.3 (both FreeBSD port and original GNU version) generates
bad code for long long operations in some cases when -O2 is on:
#include <sys/types.h>
#include <netinet/in.h>
extern off_t
rfc1035NamePack(char *buf, size_t sz, const char *name);
static off_t
rfc1035QuestionPack(char *buf, size_t sz, const char *name, unsigned short type,
unsigned short class)
{
off_t off = 0; <-- this is long long
unsigned short s;
off += rfc1035NamePack(buf, sz, name);
s = class;
memcpy(buf + off, &s, sizeof(s));
assert(off <= sz);
return off;
}
The code is taken from squid-2.3.STABLE5, it's minimized to demonstrate bug.
gcc -v -O2 -S t.c
Using builtin specs.
gcc version 2.95.3 [FreeBSD] 20010315 (release)
/usr/libexec/cpp -lang-c -v -D__GNUC__=2 -D__GNUC_MINOR__=95 -Di386 -D__FreeBSD
__=4 -D__FreeBSD_cc_version=440000 -Dunix -D__i386__ -D__FreeBSD__=4 -D__FreeBSD
_cc_version=440000 -D__unix__ -D__i386 -D__unix -Acpu(i386) -Amachine(i386) -Asy
stem(unix) -Asystem(FreeBSD) -D__OPTIMIZE__ -Acpu(i386) -Amachine(i386) -Di386 -
D__i386 -D__i386__ -D__ELF__ t.c /tmp/ccvoKazy.i
GNU CPP version 2.95.3 [FreeBSD] 20010315 (release) (i386 FreeBSD/ELF)
#include "..." search starts here:
#include <...> search starts here:
/usr/include
/usr/include
End of search list.
The following default directories have been omitted from the search path:
/usr/include/g++
End of omitted list.
/usr/libexec/cc1 /tmp/ccvoKazy.i -quiet -dumpbase t.c -O2 -version -o t.s
GNU C version 2.95.3 [FreeBSD] 20010315 (release) (i386-unknown-freebsd) compile
d by GNU C version 2.95.3 [FreeBSD] 20010315 (release).
.file "t.c"
.version "01.01"
gcc2_compiled.:
.text
.p2align 2,0x90
.type rfc1035QuestionPack,@function
rfc1035QuestionPack:
pushl %ebp
movl %esp,%ebp
subl $16,%esp
pushl %edi
pushl %esi
movl 8(%ebp),%esi
movl 12(%ebp),%eax
xorl %edx,%edx <---- this should be long long (%eax,%edx)
movl %eax,12(%ebp) <---- 2nd argument overwritten
movl %edx,16(%ebp) <---- 3rd argument overwritten
movl 24(%ebp),%edi
addl $-4,%esp
pushl 16(%ebp)
pushl %eax
pushl %esi
call rfc1035NamePack
movl %eax,-8(%ebp)
movl %edx,-4(%ebp)
movl -8(%ebp),%eax
movw %di,(%eax,%esi)
addl $-12,%esp
xorl %ecx,%ecx
movl 12(%ebp),%eax
movl 16(%ebp),%edx
addl $16,%esp
cmpl %edx,-4(%ebp)
jg .L3
jne .L4
cmpl %eax,-8(%ebp)
ja .L3
.L4:
movl $1,%ecx
.L3:
pushl %ecx
call assert
movl -8(%ebp),%eax
movl -4(%ebp),%edx
leal -24(%ebp),%esp
popl %esi
popl %esi
popl %edi
leave
ret
.Lfe1:
.size rfc1035QuestionPack,.Lfe1-rfc1035QuestionPack
.ident "GCC: (GNU) c 2.95.3 [FreeBSD] 20010315 (release)"
>How-To-Repeat:
gcc -O2 t.c
>Fix:
Use -O optimalization only. This error may manifest anywhere where long long type is used (distribution, ports). This should be mentioned
in release notes.
gcc-3.0.1 seems to be fixed.
>Release-Note:
>Audit-Trail:
>Unformatted:
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