<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">In the meantime, I put together a crude “quick” patch that removes access to the DataLayout owned by the TM in favor of the one hold by the Module:<div class=""><br class=""></div><div class=""><a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__reviews.llvm.org_D10823&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=Mfk2qtn1LTDThVkh6-oGglNfMADXfJdty4_bhmuhMHA&m=URSLwA7R-HEBSnlSZAVvRzEsZg3EhP90w0mGvYPpt6k&s=OWwLKWH_QA4MAdxUMt2CrNNWsbP8D2TbHP32B3zKSL8&e=" class="">http://reviews.llvm.org/D10823</a></div><div class=""><br class=""></div><div class="">— </div><div class="">Mehdi</div><div class=""><br class=""></div><div class=""><div><blockquote type="cite" class=""><div class="">On Jun 25, 2015, at 10:09 AM, Eric Christopher <<a href="mailto:echristo@gmail.com" class="">echristo@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Agreed. I'll reply to the rest of it soon, but if we have a required one in the module then that's what we should use.<div class=""><br class=""></div><div class="">-eric</div></div><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Thu, Jun 25, 2015 at 10:05 AM Rafael Espíndola <<a href="mailto:rafael.espindola@gmail.com" class="">rafael.espindola@gmail.com</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Long term I think we should keep only the one in the module.<br class="">
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On 24 June 2015 at 14:42, Mehdi Amini <<a href="mailto:mehdi.amini@apple.com" target="_blank" class="">mehdi.amini@apple.com</a>> wrote:<br class="">
> Hi all,<br class="">
><br class="">
> We have multiple DataLayout object in flight during a compilation: at least the one owned by the Module and the one owned by the TargetMachine.<br class="">
> There are two issues:<br class="">
> 1) What if they differ? I guess we could assert at the beginning of CodeGen.<br class="">
> 2) The DataLayout has internal mutable state (a cache of StructLayout).<br class="">
><br class="">
> The latter is my current concern: the cache in DataLayout is based on Type pointer which means that is has to be Context specific.<br class="">
> This is fine with the DataLayout attached to the Module but not with the TargetMachine.<br class="">
> The cache could live in the Context, but it is also DataLayout specific so it wouldn’t be a good fit either.<br class="">
><br class="">
> I considered modifying the cache in the DataLayout to invalidate itself when queried with a new Context, however it wouldn’t work in a multi-threaded environment (or the query would have to be behind a Mutex).<br class="">
><br class="">
> Another option is to remove the DataLayout from the TargetMachine, I tried it and it seems possible but awkward as well in some places where the DataLayout has to be supplied externally because TargetLoweringXX would not have it.<br class="">
><br class="">
> Finally the TargetMachine could be deemed to be "context-specific”, i.e. the CodeGen infrastructure would need to be reinitialized for each new Context. That would be a strong limitation though.<br class="">
><br class="">
> There may be other options?<br class="">
><br class="">
> —<br class="">
> Mehdi<br class="">
><br class="">
><br class="">
><br class="">
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