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<div class="moz-cite-prefix">On 11/05/13 11:30, Jean-Daniel Dupas
wrote:<br>
</div>
<blockquote
cite="mid:A1E7CDDE-ED39-4BB2-933C-89B6944F9792@shadowlab.org"
type="cite">
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<div>Le 5 nov. 2013 à 19:00, Behan Webster <<a
moz-do-not-send="true"
href="mailto:behanw@converseincode.com">behanw@converseincode.com</a>>
a écrit :</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
<div style="font-size: 12px; font-style: normal; font-variant:
normal; font-weight: normal; letter-spacing: normal;
line-height: normal; orphans: auto; text-align: start;
text-indent: 0px; text-transform: none; white-space: normal;
widows: auto; word-spacing: 0px; -webkit-text-stroke-width:
0px;">On 11/05/13 09:26, Konstantin Tokarev wrote:<br>
<blockquote type="cite"><br>
11.10.2013, 01:39, "Jakob Stoklund Olesen" <<a
moz-do-not-send="true" href="mailto:stoklund@2pi.dk">stoklund@2pi.dk</a>>:<br>
<blockquote type="cite">On Oct 10, 2013, at 12:32 PM,
Behan Webster <<a moz-do-not-send="true"
href="mailto:behanw@converseincode.com">behanw@converseincode.com</a>>
wrote:<br>
<br>
<blockquote type="cite">One of the issues the LLVMLinux
project is having is with the use of<br>
named registers in the Linux kernel code. The kernel
uses something like<br>
this in order to assign a C variable name to a
register (one for each<br>
kernel arch).<br>
<br>
register unsigned long current_stack_pointer
asm("esp");<br>
<br>
clang doesn't allow this kind of thing which required
a patch which less<br>
efficient:<br>
<br>
#define current_stack_pointer ({ \<br>
unsigned long esp; \<br>
asm("mov %%esp, %0" : "=r"(esp)); \<br>
esp; \<br>
})<br>
<br>
This works for both gcc and clang, but often adds in 3
extra<br>
instructions since you need to copy the stack pointer
to another<br>
register, but first that register needs to be saved to
the stack and<br>
then restored after the stackpointer has been used;
inefficient.<br>
</blockquote>
#define current_stack_pointer ({ \<br>
register unsigned long esp asm("esp"); \<br>
asm("" : "=r"(esp)); \<br>
esp; \<br>
})<br>
</blockquote>
And #ifdef it for each arch? Builtin would be much more
handy.<br>
</blockquote>
Actually no #ifdef is required with Jakob's suggestion
(works the same<br>
in both clang and gcc).<br>
<br>
</div>
</blockquote>
<div><br>
</div>
<div>It may works for both GCC and clang, it does not means it
will works with every arch linux supports (ARM, PPC, AArch, …)</div>
</div>
</blockquote>
True enough. Which is indeed another argument for
__builtin_stack_pointer().<br>
<br>
That point is precisely one of the reasons that we're pushing for
this addition.<br>
<br>
Behan<br>
<pre class="moz-signature" cols="72">--
Behan Webster
<a class="moz-txt-link-abbreviated" href="mailto:behanw@converseincode.com">behanw@converseincode.com</a></pre>
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