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<div class="moz-cite-prefix">On 04/26/2018 07:03 PM, Narayanaswamy,
Ravi wrote:<br>
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<p class="MsoNormal"><span style="color:#1F497D">Hi Hal,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> We are not
trying to address issues where the object mapped are of
different sizes between host and target with different ABI.
<br>
</span></p>
</div>
</blockquote>
<br>
Why are you not trying to address that issue?<br>
<br>
-Hal<br>
<br>
<blockquote type="cite"
cite="mid:BCFA27423AEC4E41B6CBD7B6A8C696B69B39C7AC@ORSMSX109.amr.corp.intel.com">
<div class="WordSection1">
<p class="MsoNormal"><span style="color:#1F497D"> The issue is
when the objects are of same size like double which is
8bytes on both 32bit and 64bit platform. If a double is
used in a first_private on a target clause, the 64 bit side
will pass it as value whereas on the 32bit side since the
value does not fit in the argument it will be passed as
pointer to a double. There will be a mis-match at the call
site and entry site on this value.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> The main
reason for this change is that when we do backend outlining
for target pragmas the targets information needs to be
communicated to the backend to generate the tables with the
right names. Generate LLVM IR for passing this information
is one mechanism and other is passing the command option to
the backend. For the later each pass which needs this info
will have to change.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Thanks<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Ravi<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"
style="margin-bottom:0in;margin-bottom:.0001pt;line-height:normal">
<a name="_____replyseparator" moz-do-not-send="true"></a><b><span
style="color:windowtext">From:</span></b><span
style="color:windowtext"> Hal Finkel [<a
href="mailto:hfinkel@anl.gov" moz-do-not-send="true">mailto:hfinkel@anl.gov</a>]
<br>
<b>Sent:</b> Wednesday, April 25, 2018 5:50 PM<br>
<b>To:</b> Lin, Jin <<a
href="mailto:jin.lin@intel.com" moz-do-not-send="true">jin.lin@intel.com</a>>;
Friedman, Eli <<a
href="mailto:efriedma@codeaurora.org"
moz-do-not-send="true">efriedma@codeaurora.org</a>>;
'<a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>' <<a
href="mailto:llvm-dev@lists.llvm.org"
moz-do-not-send="true">llvm-dev@lists.llvm.org</a>><br>
<b>Subject:</b> Re: [llvm-dev] [LLVM][RFC] Representing
the target device information in the LLVM IR<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p>Hi, Jin,<span style="font-size:12.0pt;line-height:105%"><o:p></o:p></span></p>
<p>Can you please back up a bit and talk about the programming
environment in which this problem manifests?<o:p></o:p></p>
<p>If I have a host and a target with different ABIs, then it
seems we have lots of problems. For one thing, the layouts of
structures are different, the sizes of some integer types are
different, the sizes of pointers are different, and so on. It
seems like a solution in this space should address, somehow,
this general translation problem. Fixing this particular
problem with the dispatch function's parameters feels like
only the tip of the iceberg. What if I'm passing a pointer to
some structure, or a pointer to other pointers, etc.?<o:p></o:p></p>
<p>I understand that OpenMP v5 is expected to have some custom
"mappers" to handle deep copying and translation. Is this
related to the design space here?<o:p></o:p></p>
<p>Thanks again,<o:p></o:p></p>
<p>Hal<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">On 04/25/2018 07:22 PM, Lin, Jin via
llvm-dev wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span style="color:#1F497D">For the
firstprivate clause, the compiler generates code to pass
it by value or by reference to the outlined function. The
reason the first private scalars is generally passed by
value is for the performance reason.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">For this
particular case, the compiler cannot generate code to pass
the double @gg by value under i386-pc-linux-gnu since the
value is 64 bit while the architecture is 32bit.
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">For the host
compilation, the compiler generates the code to pass the
data as well as the outlined function name to the OMP
runtime.
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">For the
target compilation, the compiler generates the outlined
function so that it can be called by the OMP runtime.
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">So, the
compiler is required to generate a single call on the host
to support all the targets. All the target versions must
have the same interface. So the common interface of the
outline function should be used. For this particular
example, the variable @gcc should be passed by reference
under x86_64-mic.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Please let me
know if you have more questions.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Jin</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"
style="margin-bottom:0in;margin-bottom:.0001pt;line-height:normal">
<b><span style="color:windowtext">From:</span></b><span
style="color:windowtext"> Friedman, Eli [<a
href="mailto:efriedma@codeaurora.org"
moz-do-not-send="true">mailto:efriedma@codeaurora.org</a>]
<br>
<b>Sent:</b> Wednesday, April 25, 2018 4:14 PM<br>
<b>To:</b> Lin, Jin <a
href="mailto:jin.lin@intel.com"
moz-do-not-send="true"><jin.lin@intel.com></a>;
'<a href="mailto:llvm-dev@lists.llvm.org"
moz-do-not-send="true">llvm-dev@lists.llvm.org</a>'
<a href="mailto:llvm-dev@lists.llvm.org"
moz-do-not-send="true"><llvm-dev@lists.llvm.org></a><br>
<b>Subject:</b> Re: [llvm-dev] [LLVM][RFC]
Representing the target device information in the LLVM
IR</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<p class="MsoNormal">On 4/25/2018 3:48 PM, Lin, Jin wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span style="color:#0070C0">Given a
global variable @gg, the compiler has to generate code
on the host to specify whether it is passed by value or
passed by reference. In the following example, if the
compiler generates the code for passing by value, the
outlined function on the target </span><span
style="font-family:"color:#0070C0;border:none
windowtext 1.0pt;padding:0in">i386-pc-linux-gnu</span><span
style="color:#0070C0"> cannot get the correct value
since it assumes the variable @gg is passed by
reference. </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#0070C0"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#0070C0">Here is the
corresponding IR on the host side.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:red"> %0 = load
double, double* @gg, align 8, !tbaa !3</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:red"> %1 = bitcast
double %0 to i64</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> …</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#0070C0"> %12 =
getelementptr inbounds [4 x i8*], [4 x i8*]*
%.offload_baseptrs, i32 0, i32 2</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#0070C0"> %13 =
bitcast i8** %12 to i64*</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:red"> store i64 %1,
i64* %13, align 8</span><o:p></o:p></p>
</blockquote>
<p class="MsoNormal"
style="margin-bottom:12.0pt;line-height:normal"><span
style="font-size:12.0pt;font-family:"Times New Roman
,serif",serif"><br>
Could you describe the overall process of calling an
offloaded function in a bit more detail? How do you
describe the ABI of the called function to the OpenMP
runtime?<br>
<br>
I suspect you shouldn't be trying to store things which
aren't pointers into offload_baseptrs.<br>
<br>
-Eli<br>
<br>
<br>
</span><o:p></o:p></p>
<pre>-- <o:p></o:p></pre>
<pre>Employee of Qualcomm Innovation Center, Inc.<o:p></o:p></pre>
<pre>Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project<o:p></o:p></pre>
<p class="MsoNormal"
style="margin-bottom:12.0pt;line-height:normal"><span
style="font-size:12.0pt;font-family:"Times New
Roman",serif"><br>
<br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>LLVM Developers mailing list<o:p></o:p></pre>
<pre><a href="mailto:llvm-dev@lists.llvm.org" moz-do-not-send="true">llvm-dev@lists.llvm.org</a><o:p></o:p></pre>
<pre><a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" moz-do-not-send="true">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><o:p></o:p></pre>
</blockquote>
<p class="MsoNormal"
style="margin-bottom:12.0pt;line-height:normal"><span
style="font-size:12.0pt;font-family:"Times New
Roman",serif"><o:p> </o:p></span></p>
<pre>-- <o:p></o:p></pre>
<pre>Hal Finkel<o:p></o:p></pre>
<pre>Lead, Compiler Technology and Programming Languages<o:p></o:p></pre>
<pre>Leadership Computing Facility<o:p></o:p></pre>
<pre>Argonne National Laboratory<o:p></o:p></pre>
</div>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory</pre>
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