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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Rematerial address for literal string pool"
href="https://llvm.org/bugs/show_bug.cgi?id=31228">31228</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Rematerial address for literal string pool
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>weimingz@codeaurora.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>given test.c:
extern void mylog(const char*);
#define LOG(msg) { static const char __attribute__((section("logstrings")))
mystring[] = #msg; mylog(mystring); }
void test() {
LOG("this is log msg 0");
LOG("this is log msg 11");
LOG("this is log msg 222");
LOG("this is log msg 3333");
}
The code puts all string literals in the same section. GCC is able to
rematerial the address:
arm-linux-gnueabi-gcc -mcpu=cortex-m3 -Os
push {r4, lr}
ldr r4, .L2
mov r0, r4
bl mylog
add r0, r4, #20
bl mylog
add r0, r4, #40
bl mylog
add r0, r4, #60
pop {r4, lr}
b mylog
but LLVM generates larger code:
clang -mcpu=cortex-m3 -target armv7m-linux-gnueabi -c -Os
push {r7, lr}
.setfp r7, sp
mov r7, sp
movw r0, :lower16:test.mystring
movt r0, :upper16:test.mystring
bl mylog
movw r0, :lower16:test.mystring.1
movt r0, :upper16:test.mystring.1
bl mylog
movw r0, :lower16:test.mystring.2
movt r0, :upper16:test.mystring.2
bl mylog
movw r0, :lower16:test.mystring.3
movt r0, :upper16:test.mystring.3
pop.w {r7, lr}
b mylog</pre>
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