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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Adding Ziv, the author of this patch.<o:p></o:p></span></p>
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></a></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Chandler Carruth [mailto:chandlerc@google.com]
<br>
<b>Sent:</b> Thursday, December 29, 2016 11:57<br>
<b>To:</b> Yatsina, Marina <marina.yatsina@intel.com>; cfe-commits@lists.llvm.org<br>
<b>Subject:</b> Re: r290539 - [inline-asm]No error for conflict between inputs\outputs and clobber list<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Mon, Dec 26, 2016 at 4:34 AM Marina Yatsina via cfe-commits <<a href="mailto:cfe-commits@lists.llvm.org">cfe-commits@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Author: myatsina<br>
Date: Mon Dec 26 06:23:42 2016<br>
New Revision: 290539<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=290539&view=rev" target="_blank">
http://llvm.org/viewvc/llvm-project?rev=290539&view=rev</a><br>
Log:<br>
[inline-asm]No error for conflict between inputs\outputs and clobber list<br>
<br>
According to extended asm syntax, a case where the clobber list includes a variable from the inputs or outputs should be an error - conflict.<br>
for example:<br>
<br>
const long double a = 0.0;<br>
int main()<br>
{<br>
<br>
char b;<br>
double t1 = a;<br>
__asm__ ("fucompp": "=a" (b) : "u" (t1), "t" (t1) : "cc", "st", "st(1)");<br>
<br>
return 0;<br>
}<br>
<br>
This should conflict with the output - t1 which is st, and st which is st aswell.<br>
The patch fixes it. <o:p></o:p></p>
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<p class="MsoNormal"><br>
Commit on behald of Ziv Izhar.<br>
<br>
Differential Revision: <a href="https://reviews.llvm.org/D15075" target="_blank">
https://reviews.llvm.org/D15075</a><br>
<br>
<br>
Modified:<br>
cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td<br>
cfe/trunk/include/clang/Basic/TargetInfo.h<br>
cfe/trunk/lib/Basic/TargetInfo.cpp<br>
cfe/trunk/lib/Basic/Targets.cpp<br>
cfe/trunk/lib/Headers/intrin.h<br>
cfe/trunk/lib/Sema/SemaStmtAsm.cpp<br>
cfe/trunk/test/Sema/asm.c<br>
<br>
Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=290539&r1=290538&r2=290539&view=diff" target="_blank">
http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=290539&r1=290538&r2=290539&view=diff</a><br>
==============================================================================<br>
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)<br>
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Mon Dec 26 06:23:42 2016<br>
@@ -7069,6 +7069,10 @@ let CategoryName = "Inline Assembly Issu<br>
"constraint '%0' is already present here">;<br>
}<br>
<br>
+ def error_inoutput_conflict_with_clobber : Error<<br>
+ "asm-specifier for input or output variable conflicts with asm"<br>
+ " clobber list">;<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Clang generally works to avoid this kind of error message. All this does is say "there was a problem of this kind" without identifying any of the specifics. And for this error in particular I think this is of the utmost importance. Developers
are not going to understand what went wrong here.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I would suggest at a minimum to enhance this to explain:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">1) What operands and clobbers conflict, preferably with source ranges underlining them.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">2) Why they conflict (for example the fact that "D" means the di register group, of which "%rdi" is a member)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Beyond that, I wonder if you could add a note suggesting to remove the clobber if the input (or output) operand is sufficient.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">You can make this note explain carefully the case where something would need to be added to the inputs or outputs instead, but I think it at least makes sense to clarify that this will be a common fix and what to look out for that might
make it an incorrect fix.<o:p></o:p></p>
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