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[Bug target/29198] New: Incorrect reference to __thread array with -fPIC -O2 on x86
- From: "ian at airs dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 24 Sep 2006 05:21:48 -0000
- Subject: [Bug target/29198] New: Incorrect reference to __thread array with -fPIC -O2 on x86
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
I compiled this C code with current mainline with -fPIC -O2 on x86 GNU/Linux:
extern int f2 (int, int, int, int);
struct s { char b[4]; };
__thread struct s a[2];
void f1 (int a1, int a2)
{
int i, j;
for (i = 0; i < 4; i++)
{
int tot = 0;
for (j = 0; j < 4; j++)
tot += f2 (a1, a2, i, j);
a[0].b[i] = tot;
}
}
The resulting assembler file had this in it:
movl a@GOT(%ebx), %ecx
But a is declared with __thread. This should instead be something like:
leal a@TLSGD(,%ebx,1), %eax
call ___tls_get_addr@PLT
In the real code there are other references to a, which leads to a linker
error:
`a' accessed both as normal and thread local symbol
I believe the bug is in legitimize_address or in legitimize_pic_address in
config/i386/i386.c. legitimize_address gets called with
(plus:SI (reg/v:SI 64 [ i ])
(symbol_ref:SI ("a") [flags 0x8] <var_decl 0xb7c630b0 a>))
When it sees a symbol as the right-hand operand of a PLUS, it calls
legitimize_pic_address. That returns an UNSPEC_GOT. Somewhere along the way,
it needs to call legitimize_tls_address.
--
Summary: Incorrect reference to __thread array with -fPIC -O2 on
x86
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: ian at airs dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198