<div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div>Hi,</div><div>I hope this can help someone else, I manually modified the IR in this way</div><div><br></div><div>...</div><div>%8 = load i8*, i8** %7, align 8<br> %9 = load i8, i8* %8, align 4<br> %10 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i8* %8)<br> %11 = load i32, i32* %4, align 4<br> ret i32 %11<br>...</div><div><br></div><div>At this point it is enough to cast %9: const char *target = (const char *)v.PointerVal;</div><div><br></div><div>So it should be enough just to read from that memory address as expected :)</div><div><br></div><div>Thanks anyway<br></div></div></div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Il giorno dom 27 gen 2019 alle ore 08:03 Alberto Barbaro <<a href="mailto:barbaro.alberto@gmail.com">barbaro.alberto@gmail.com</a>> ha scritto:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto"><div>Hi,<div dir="auto">No problem at all. Yes I think a good subject would help.</div><div dir="auto"><br></div><div dir="auto">I didn't know about the IRC channel :)</div><div dir="auto"><br></div><div dir="auto">Thanks again, really appreciated</div><br><br><div class="gmail_quote"><div dir="ltr">On Sun, Jan 27, 2019, 01:25 Doerfert, Johannes Rudolf <<a href="mailto:jdoerfert@anl.gov" target="_blank">jdoerfert@anl.gov</a> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div id="gmail-m_-2844149971407340398m_7535242729923710443divtagdefaultwrapper" style="font-size:12pt;color:rgb(0,0,0);font-family:Calibri,Helvetica,sans-serif" dir="ltr">
<p style="margin-top:0px;margin-bottom:0px">I now get your intent but can't really help you. You need to ask interpreter folks.</p>
<p style="margin-top:0px;margin-bottom:0px"><br>
</p>
<p style="margin-top:0px;margin-bottom:0px">I'd suggest you send another email, state clearly what you want, and put a summary in the subject line.</p>
<p style="margin-top:0px;margin-bottom:0px">You can also try the IRC, though during the week you might have more luck.<br>
</p>
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<hr style="display:inline-block;width:98%">
<div id="gmail-m_-2844149971407340398m_7535242729923710443divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> Alberto Barbaro <<a href="mailto:barbaro.alberto@gmail.com" rel="noreferrer" target="_blank">barbaro.alberto@gmail.com</a>><br>
<b>Sent:</b> Saturday, January 26, 2019 7:07:26 PM<br>
<b>To:</b> Doerfert, Johannes Rudolf<br>
<b>Cc:</b> llvm-dev<br>
<b>Subject:</b> Re: [llvm-dev] (no subject)</font>
<div> </div>
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<div dir="auto">
<div>Hi,
<div dir="auto">All good points and jokes in your email :)</div>
<div dir="auto"><br>
</div>
<div dir="auto">My final goal is the get the value of %8 at runtime. So considering the program is called argv I would like to execute something like ./argv 22 and get the value of argv[0]. Is it possible? So far I have the address where the parameter at position
0 in store but I'd like to read the value and print it.</div>
<div dir="auto"><br>
</div>
<div dir="auto">I hope it is clear now</div>
<div dir="auto"><br>
</div>
<div dir="auto">Thanks again</div>
<br>
<br>
<div class="gmail-m_-2844149971407340398m_7535242729923710443x_gmail_quote">
<div dir="ltr">On Fri, Jan 25, 2019, 06:23 Doerfert, Johannes Rudolf <<a href="mailto:jdoerfert@anl.gov" rel="noreferrer" target="_blank">jdoerfert@anl.gov</a> wrote:<br>
</div>
<blockquote class="gmail-m_-2844149971407340398m_7535242729923710443x_gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
On 01/20, Alberto Barbaro via llvm-dev wrote:<br>
> Hi all,<br>
> I have the following C code:<br>
> <br>
> #include<stdio.h><br>
> <br>
> int main(int argc, char *argv[]) {<br>
> <br>
> printf("%s\n", argv[0]);<br>
> return argc;<br>
> }<br>
> <br>
> that generates the following IR for the main function:<br>
> <br>
> ; Function Attrs: noinline nounwind optnone uwtable<br>
> define i32 @main(i32, i8**) #0 {<br>
> %3 = alloca i32, align 4<br>
> %4 = alloca i32, align 4<br>
> %5 = alloca i8**, align 8<br>
> store i32 0, i32* %3, align 4<br>
> store i32 %0, i32* %4, align 4<br>
> store i8** %1, i8*** %5, align 8<br>
> %6 = load i8**, i8*** %5, align 8<br>
> %7 = getelementptr inbounds i8*, i8** %6, i64 0<br>
> %8 = load i8*, i8** %7, align 8<br>
> %9 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4<br>
> x i8]* @.str, i32 0, i32 0), i8* %8)<br>
> %10 = load i32, i32* %4, align 4<br>
> ret i32 %10<br>
> }<br>
<br>
You should really run -mem2reg (without the optnone though). Also<br>
-instcombine is afterwards often helpful to clean up clang generated<br>
code, or maybe just run it with -O1.<br>
<br>
> I think %8 will contain the address of argv[0], so %7 was storing a pointer<br>
> to pointer to argv? I'm not sure of that.<br>
<br>
Let's see: argc is %0 and argv == &argv[0] is %1. The latter is stored<br>
in %5, which is loaded as %6. The GEP (%7) is a no-op, thus %6 == %7.<br>
Finally, %8 is the value argv[0] of type char/i8.<br>
<br>
> Considering that I can access the GenericValue set by<br>
> visitGetElementPtrInst. How can I obtain the value of argv[0] at runtime<br>
> using the Interpreter class?<br>
<br>
Sorry can't help with that. I don't know the Interpreter class and I<br>
guess "GenericValue" and "visitGetElementPtrInst" are somehow related to<br>
it.<br>
<br>
> Thanks<br>
<br>
> _______________________________________________<br>
> LLVM Developers mailing list<br>
> <a href="mailto:llvm-dev@lists.llvm.org" rel="noreferrer noreferrer" target="_blank">llvm-dev@lists.llvm.org</a><br>
> <a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" rel="noreferrer noreferrer noreferrer" target="_blank">
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><br>
<br>
<br>
-- <br>
<br>
Johannes Doerfert<br>
Researcher<br>
<br>
Argonne National Laboratory<br>
Lemont, IL 60439, USA<br>
<br>
<a href="mailto:jdoerfert@anl.gov" rel="noreferrer noreferrer" target="_blank">jdoerfert@anl.gov</a><br>
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