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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">+1 for "isa_nonnull"<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>
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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-dev [mailto:llvm-dev-bounces@lists.llvm.org]
<b>On Behalf Of </b>Hubert Tong via llvm-dev<br>
<b>Sent:</b> Friday, April 05, 2019 12:10 AM<br>
<b>To:</b> Aaron Ballman<br>
<b>Cc:</b> LLVM Development List<br>
<b>Subject:</b> Re: [llvm-dev] [RFC] Should we add isa_or_null<>?<o:p></o:p></span></p>
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<p class="MsoNormal">On Thu, Apr 4, 2019 at 11:15 PM Aaron Ballman via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">On Thu, Apr 4, 2019 at 12:58 PM Chris Lattner <<a href="mailto:clattner@nondot.org" target="_blank">clattner@nondot.org</a>> wrote:<br>
><br>
><br>
><br>
> > On Apr 4, 2019, at 5:37 AM, Don Hinton via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>> wrote:<br>
> ><br>
> > I'd like to propose adding `isa_or_null<>` to replace the following usage pattern that's relatively common in conditionals:<br>
> ><br>
> > var && isa<T>(var) =>> isa_or_null<T>(var)<br>
> ><br>
> > And in particular when `var` is a method call which might be expensive, e.g.:<br>
> ><br>
> > X->foo() && isa<T>(X->foo()) =>> isa_or_null<T>(X->foo())<br>
> ><br>
> > The implementation could be a simple wrapper around isa<>, and while the IR produced is only slightly more efficient, the elimination of an extra call could be worthwhile.<br>
><br>
> I’d love to see this, I agree with downstream comments though that this name will be confusing. isa_and_nonnull<>. ?<br>
<br>
tbh, I don't think the proposed name will be all that confusing --<br>
we're used to _or_null() returning "the right thing" when given null.<br>
isa_and_nonnull<> is a bit of a weird name for me, but I could<br>
probably live with it. We could spell it nonnull_and_isa<> to reflect<br>
the order of the operations, but that sort of hides the important part<br>
of the API (the "isa" bit).<o:p></o:p></p>
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<p class="MsoNormal">I think "isa_nonnull" would read fine too. To me, the extra "and" makes the ordering more of an issue.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">-- HT<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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~Aaron<br>
<br>
><br>
> -Chris<br>
><br>
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