Soon to be attached asm dump is produced by compiling:
__thread a;
int
main ()
{
a = 0;
}
with -O2 -fpic on native-TLS architecture.
To show the problem, a tlsgd load was changed from:
lda $16,a($29) !tlsgd!1
to:
lda $15,a($29) !tlsgd!1
mov $15,$16
(this change illustrates real code, produced by compiling the testcase from
gcc.dg/tls/opt-12.c.
The object file is still OK (see insn at 0x10):
0000000000000000 <main>:
0: 00 00 bb 27 ldah gp,0(t12)
4: 00 00 bd 23 lda gp,0(gp)
8: f0 ff de 23 lda sp,-16(sp)
c: 1f 04 ff 5f fnop
> 10: 00 00 fd 21 lda fp,0(gp) <<<<< HERE
14: 10 04 ef 47 mov fp,a0
18: 00 00 7d a7 ldq t12,0(gp)
1c: 00 00 5e b7 stq ra,0(sp)
20: 00 40 5b 6b jsr ra,(t12),24 <main+0x24>
24: 00 00 ba 27 ldah gp,0(ra)
28: 00 00 5e a7 ldq ra,0(sp)
2c: 00 00 e0 b3 stl zero,0(v0)
30: 00 00 bd 23 lda gp,0(gp)
34: 10 00 de 23 lda sp,16(sp)
38: 01 80 fa 6b ret
3c: 00 00 fe 2f unop
However, final link changes target reg in the marked insn from fp to a0:
0000000120000640 <main>:
120000640: 02 00 bb 27 ldah gp,2(t12)
120000644: d0 99 bd 23 lda gp,-26160(gp)
120000648: f0 ff de 23 lda sp,-16(sp)
12000064c: 1f 04 ff 5f fnop
> 120000650: 10 00 1f 22 lda a0,16
120000654: 10 04 ef 47 mov fp,a0
120000658: 00 00 fe 2f unop
12000065c: 00 00 5e b7 stq ra,0(sp)
120000660: 9e 00 00 00 rduniq
120000664: 00 04 00 42 addq a0,v0,v0
120000668: 00 00 5e a7 ldq ra,0(sp)
12000066c: 00 00 e0 b3 stl zero,0(v0)
120000670: 00 00 fe 2f unop
120000674: 10 00 de 23 lda sp,16(sp)
120000678: 01 80 fa 6b ret
12000067c: 00 00 fe 2f unop
There is no need for this "fixup".
--
Summary: linker changes target register in tlsgd load
Product: binutils
Version: 2.20
Status: NEW
Severity: normal
Priority: P2
Component: ld
AssignedTo: unassigned at sources dot redhat dot com
ReportedBy: ubizjak at gmail dot com
CC: bug-binutils at gnu dot org
GCC build triplet: alphaev68-pc-linux-gnu
GCC host triplet: alphaev68-pc-linux-gnu
GCC target triplet: alphaev68-pc-linux-gnu
http://sourceware.org/bugzilla/show_bug.cgi?id=11891
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