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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">New patch #3. I’ll get a new #2 out when I can, but that needs more extensive rework.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> llvm-commits-bounces@cs.uiuc.edu [mailto:llvm-commits-bounces@cs.uiuc.edu]
<b>On Behalf Of </b>Robinson, Paul<br>
<b>Sent:</b> Monday, November 18, 2013 12:16 PM<br>
<b>To:</b> Bill Wendling<br>
<b>Cc:</b> llvm-commits@cs.uiuc.edu commits (llvm-commits@cs.uiuc.edu)<br>
<b>Subject:</b> RE: [PATCH] Implement ‘optnone’ attribute semantics<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I think taking out the TargetOptions piece mostly wouldn’t interfere with the basic use-case, which is to make debugging easy. It does mean fiddling with how
FastISel is enabled, so in SelectionDAGISel::SelectAllBasicBlocks we’d do something like change<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoPlainText">if (TM.Options.EnableFastISel)<o:p></o:p></p>
<p class="MsoPlainText"> FastIS = ...<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">to<o:p></o:p></span></p>
<p class="MsoPlainText">if (TM.Options.EnableFastISel || Fn.hasFnAttribute(Attribute::OptimizeNone))<o:p></o:p></p>
<p class="MsoPlainText"> FastIS = ...<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">If we still reset the OptLevel to 0 then when FastISel bails out, regular ISel shouldn’t get too ambitious.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Does that seem reasonable? I’ll post a revised patch in a bit that does this. Also the early-exit tweak.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Bill Wendling [<a href="mailto:isanbard@gmail.com">mailto:isanbard@gmail.com</a>]
<br>
<b>Sent:</b> Monday, November 18, 2013 12:18 AM<br>
<b>To:</b> Robinson, Paul<br>
<b>Cc:</b> <a href="mailto:llvm-commits@cs.uiuc.edu">llvm-commits@cs.uiuc.edu</a> commits (<a href="mailto:llvm-commits@cs.uiuc.edu">llvm-commits@cs.uiuc.edu</a>)<br>
<b>Subject:</b> Re: [PATCH] Implement ‘optnone’ attribute semantics<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">On Nov 13, 2013, at 4:09 PM, Robinson, Paul <<a href="mailto:Paul_Robinson@playstation.sony.com">Paul_Robinson@playstation.sony.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">I am energized by positive discussions of the 'optnone' attribute<br>
during the dev meeting last week, so here we go.<br>
<br>
Some time ago Andrea Di Biagio committed a patch to define an 'optnone'<br>
attribute in the LLVM IR; he has since passed the torch to me on this<br>
one, so I'm attaching 3 patches to implement the semantics we want.<br>
<br>
While the patches all address semantics of 'optnone' I should point<br>
out that (I'm pretty sure) they are independent of each other and<br>
don't have to be reviewed sequentially, or anything like that.<br>
<br>
Patch #3 deals with the codegen stuff. Basically, an 'optnone'<br>
function will be treated as if it were compiled at -O0; this is a<br>
little easier to accomplish than it is for IR-level passes.<o:p></o:p></p>
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<p class="MsoNormal">You changes in Patch #3 won’t work. You’re changing the TargetOptions settings, but that violates what the back-end is expecting. For instance, the UnsafeFPMath is used during the creation of the back-end to register which actions to perform
for which operations. E.g., in X86ISelLowering.cpp <span style="color:#71C2C1">X86TargetLowering</span>::<span style="color:#5E34FF">resetOperationActions()</span>:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<div>
<p class="MsoNormal"> <span style="color:#D03CFF">if</span> (!TM.Options.<span style="background:#AFFEFF">UnsafeFPMath</span>) {<o:p></o:p></p>
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<p class="MsoNormal"> setOperationAction(<span style="color:#71C2C1">ISD</span>::FSIN ,
<span style="color:#71C2C1">MVT</span>::f64, Expand);<o:p></o:p></p>
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<p class="MsoNormal"> setOperationAction(<span style="color:#71C2C1">ISD</span>::FCOS ,
<span style="color:#71C2C1">MVT</span>::f64, Expand);<o:p></o:p></p>
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<p class="MsoNormal"> setOperationAction(<span style="color:#71C2C1">ISD</span>::FSINCOS,
<span style="color:#71C2C1">MVT</span>::f64, Expand);<o:p></o:p></p>
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<p class="MsoNormal"> }<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Is it possible to do FastISel only as an initial stage?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Also, use early exits whenever possible. E.g., this<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<div>
<p class="MsoNormal">+ ~OptLevelChanger() {<o:p></o:p></p>
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<p class="MsoNormal">+ if (IS.OptLevel != SavedOptLevel) {<o:p></o:p></p>
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<p class="MsoNormal">+ DEBUG(dbgs() << "\nRestoring optimization level for Function "<o:p></o:p></p>
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<p class="MsoNormal">+ << IS.MF->getFunction()->getName() << "\n");<o:p></o:p></p>
</div>
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<p class="MsoNormal">+ DEBUG(dbgs() << "\tBefore: -O" << IS.OptLevel<o:p></o:p></p>
</div>
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<p class="MsoNormal">+ << " ; After: -O" << SavedOptLevel << "\n");<o:p></o:p></p>
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<p class="MsoNormal">+ IS.OptLevel = SavedOptLevel;<o:p></o:p></p>
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<p class="MsoNormal">+ IS.TM.setOptLevel(SavedOptLevel);<o:p></o:p></p>
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<p class="MsoNormal">+ }<o:p></o:p></p>
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<p class="MsoNormal">+ }<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<div>
<p class="MsoNormal">could be this:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<div>
<p class="MsoNormal">+ ~OptLevelChanger() {<o:p></o:p></p>
</div>
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<p class="MsoNormal">+ if (IS.OptLevel == SavedOptLevel)<o:p></o:p></p>
</div>
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<p class="MsoNormal">+ return<o:p></o:p></p>
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<p class="MsoNormal">+ DEBUG(dbgs() << "\nRestoring optimization level for Function "<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">+ << IS.MF->getFunction()->getName() << "\n");<o:p></o:p></p>
</div>
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<p class="MsoNormal">+ DEBUG(dbgs() << "\tBefore: -O" << IS.OptLevel<o:p></o:p></p>
</div>
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<p class="MsoNormal">+ << " ; After: -O" << SavedOptLevel << "\n");<o:p></o:p></p>
</div>
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<p class="MsoNormal">+ IS.OptLevel = SavedOptLevel;<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">+ IS.TM.setOptLevel(SavedOptLevel);<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">+ }<o:p></o:p></p>
</div>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</div>
<div>
<p class="MsoNormal">-bw<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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