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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - need arm llvm -fpie to work without __aeabi_read_tp"
href="https://llvm.org/bugs/show_bug.cgi?id=23566">23566</a>
</td>
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<th>Summary</th>
<td>need arm llvm -fpie to work without __aeabi_read_tp
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: ARM
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>chh@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Current clang generates references to __aeabi_read_tp
for arm target under -fpie.
It generates references to __tls_get_addr under -fPIC,
and no special library reference under -fpie for x86 target.
The reference to __aeabi_read_tp caused link time error
because Android run-time library does not have this function yet.
Gcc for arm target generates references to __emutls_get_address under -fpie or
-fPIC.
Is there any clang arm target configuration flag to generate
for -fpie references to __tls_get_addr or __emutls_get_address,
or no external reference at all?
This will allow existing AOSP upstream projects to continue using -fpie,
instead of -fPIC or waiting for an upgrade of AOSP library.
The folloing is a test case reduced from Android Open Source
external/fio/gettime.c
It shows that reference to __aeabi_read_tp is used only for arm -fpie,
not for -fPIC or x86.
$ cat g.i.c
struct mytimeval {
int tv_sec;
int tv_usec;
};
struct tv_valid {
struct mytimeval last_tv;
int last_tv_valid;
};
extern __thread struct tv_valid static_tv_valid;
void fio_gettime(struct mytimeval *tp)
{
struct tv_valid *tv = &static_tv_valid;
if (tv) {
if (tv->last_tv_valid)
tp->tv_sec = tv->last_tv.tv_sec;
tv->last_tv_valid = 1;
}
}
$ clang -fpie g.i.c -c -o /tmp/c.x86.pie.o
$ clang -fPIC g.i.c -c -o /tmp/c.x86.PIC.o
$ clang -target arm-linux-androideabi -fpie g.i.c -c -o /tmp/c.pie.o
$ clang -target arm-linux-androideabi -fPIC g.i.c -c -o /tmp/c.PIC.o
$ nm /tmp/c.x86.pie.o | grep -E 'aeabi_read|tls_'
$ nm /tmp/c.x86.PIC.o | grep -E 'aeabi_read|tls_'
U __tls_get_addr
$ nm /tmp/c.pie.o | grep -E 'aeabi_read|tls_'
U __aeabi_read_tp
$ nm /tmp/c.PIC.o | grep -E 'aeabi_read|tls_'
U __tls_get_addr</pre>
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