<html><body><div style="font-family: times new roman, new york, times, serif; font-size: 12pt; color: #000000"><div>Hi John,</div><div><br></div><div>Thank you for your answer. I tried <span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;">ImmutablePasses, while the problem came again.</span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;">Because the W need some information like loopinfo, so I need LoopInfo *LI = &getAnalysis<LoopInfo>(F); in this ImmutablePasses, and Function or Module are needed.</span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;">I didn't find a way to get the Module or Function in ImmutablePasses.</span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><br></span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;">So, 1, can I use <span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;">LoopInfo *LI = &getAnalysis<LoopInfo>(F); in ImmutablePasses?</span></span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;">2, is there a method to get the Module in ImmutablePasses?</span></span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><br></span></span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;">Thank you!</span></span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><br></span></span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;">Sincerely,</span></span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><br></span></span></div><div><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica, Arial, sans-serif;" data-mce-style="font-family: Helvetica, Arial, sans-serif;">Hanbing</span></span></div><div><br></div><hr id="zwchr"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;" data-mce-style="border-left: 2px solid #1010FF; margin-left: 5px; padding-left: 5px; color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><b>De: </b>"John Criswell" <criswell@illinois.edu><br><b>À: </b>"Hanbing Li" <hanbing.li@inria.fr>, llvmdev@cs.uiuc.edu<br><b>Envoyé: </b>Samedi 5 Avril 2014 00:27:13<br><b>Objet: </b>Re: [LLVMdev] Add a new information and preserve it in LLVM<br><div><br></div><div class="moz-cite-prefix">On 4/4/14 3:02 PM, Hanbing Li wrote:<br></div><blockquote cite="mid:155431169.2722035.1396641779298.JavaMail.zimbra@inria.fr"><div style="font-family: times new roman, new york, times, serif;
font-size: 12pt; color: #000000" data-mce-style="font-family: times new roman, new york, times, serif; font-size: 12pt; color: #000000;"><div><p style="margin: 0px; font-size: 12px; font-family:
Helvetica;" data-mce-style="margin: 0px; font-size: 12px; font-family: Helvetica;">Hello,</p><p style="margin: 0px; font-size: 12px; font-family:
Helvetica; min-height: 14px;" data-mce-style="margin: 0px; font-size: 12px; font-family: Helvetica; min-height: 14px;"><br></p><p style="margin: 0px; font-size: 12px; font-family:
Helvetica;" data-mce-style="margin: 0px; font-size: 12px; font-family: Helvetica;"><span class="Apple-tab-span" style="white-space: pre;" data-mce-style="white-space: pre;"> </span>I am trying to add some thing into LLVM, while I encountered some problems.</p><p style="margin: 0px; font-size: 12px; font-family:
Helvetica; min-height: 14px;" data-mce-style="margin: 0px; font-size: 12px; font-family: Helvetica; min-height: 14px;"><br></p><p style="margin: 0px; font-size: 12px; font-family:
Helvetica;" data-mce-style="margin: 0px; font-size: 12px; font-family: Helvetica;"><span class="Apple-tab-span" style="white-space: pre;" data-mce-style="white-space: pre;"> </span>So my situation is that I have some information W, some transform passes may change it, after these passes, I need the new W. What I did is to create an analysis pass similar to scalar-evolution or loopinfo, I can get the information by using getAnalysis<W>(); and preserve this information W by using AU.addPreserved<W>();. Then the problem came, for the module pass, the information can’t be preserved. (I found this: <span style="font-size: 13px; font-family: Courier;" data-mce-style="font-size: 13px; font-family: Courier;">To the best of my knowledge, the LLVM pass manager never preserves a FunctionPass analysis that is requested by a ModulePass; every time you call getAnalysis for a function, the FunctionPass is re-run. <a class="moz-txt-link-freetext" href="http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-March/048139.html" target="_blank" data-mce-href="http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-March/048139.html">http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-March/048139.html</a></span>) So this means that I can’t update W when some module passes changed it?</p><p style="margin: 0px; font-size: 12px; font-family:
Helvetica; min-height: 14px;" data-mce-style="margin: 0px; font-size: 12px; font-family: Helvetica; min-height: 14px;"><br></p><p style="margin: 0px; font-size: 12px; font-family:
Helvetica;" data-mce-style="margin: 0px; font-size: 12px; font-family: Helvetica;">My questions are:</p><p style="margin: 0px; font-size: 12px; font-family:
Helvetica;" data-mce-style="margin: 0px; font-size: 12px; font-family: Helvetica;">1, Module pass really can’t preserve the W?</p></div></div></blockquote><br> If W is a FunctionPass, then I believe you are correct: a ModulePass will re-run the FunctionPass every time it uses the FunctionPass.<br> <br> I get the impression that you're using the PassManager infrastructure improperly, and that is probably why you're not getting the results you want.<br> <br> First, the ability to preserve a pass's results with addPreserved<W>() is an optimization. A FunctionPass or ModulePass() that analyzes the LLVM IR should work whether it is run one time or a hundred times. The addPreserved<>() functionality is only there so that the LLVM compiler can cache the results of analysis passes for efficiency.<br> <br> Second, the way to fix your problem depends on what you want to do. If you want pass W to analyze the LLVM IR of a program and cache its results (because the analysis it does is expensive), then make it a ModulePass. That way, other ModulePass'es can update and preserve its results.<br> <br> If you are just using W as a container in which to record information that transform passes are doing, then you might want to make W an ImmutablePass. ImmutablePasses are only run once and are never invalidated; other passes can use them to record information about what they do. ImmutablePasses, I think, were not really designed for this purpose, but they'll get the job done.<br> <br> Regards,<br> <br> John Criswell<br> <br></blockquote><div><br></div></div></body></html>