<div dir="ltr">What's the advantage of moving the dtor to be out of line and act as a key function? I Think when I originally added a bunch of these Chris Lattner mentioned a slight preference towards an explicit anchor rather than placing the dtor out of line (if it wasn't already) - since the latter might inhibit optimizations like inlining of the dtor in some cases (even with a virtual dtor - not all dtor calls might be virtual, and derived dtors need to call the base dtor, etc).<br><br>Oh, looks like the key function/weak vtable issue was removed from the style guide at some point - maybe we can/should just rip out all the explicit anchors, then?</div><br><div class="gmail_quote"><div dir="ltr">On Fri, Jul 27, 2018 at 4:12 PM Fangrui Song via llvm-commits <<a href="mailto:llvm-commits@lists.llvm.org">llvm-commits@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: maskray<br>
Date: Fri Jul 27 16:12:11 2018<br>
New Revision: 338175<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=338175&view=rev" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project?rev=338175&view=rev</a><br>
Log:<br>
[Support] Remove unnecessary MemoryBuffer::anchor (where the destructor serves as the key function)<br>
<br>
Modified:<br>
    llvm/trunk/include/llvm/Support/MemoryBuffer.h<br>
    llvm/trunk/include/llvm/Support/SmallVectorMemoryBuffer.h<br>
    llvm/trunk/lib/Support/MemoryBuffer.cpp<br>
<br>
Modified: llvm/trunk/include/llvm/Support/MemoryBuffer.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/MemoryBuffer.h?rev=338175&r1=338174&r2=338175&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/MemoryBuffer.h?rev=338175&r1=338174&r2=338175&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/Support/MemoryBuffer.h (original)<br>
+++ llvm/trunk/include/llvm/Support/MemoryBuffer.h Fri Jul 27 16:12:11 2018<br>
@@ -43,7 +43,6 @@ class MemoryBuffer {<br>
   const char *BufferStart; // Start of the buffer.<br>
   const char *BufferEnd;   // End of the buffer.<br>
<br>
-<br>
 protected:<br>
   MemoryBuffer() = default;<br>
<br>
@@ -148,9 +147,6 @@ public:<br>
   virtual BufferKind getBufferKind() const = 0;<br>
<br>
   MemoryBufferRef getMemBufferRef() const;<br>
-<br>
-private:<br>
-  virtual void anchor();<br>
 };<br>
<br>
 /// This class is an extension of MemoryBuffer, which allows copy-on-write<br>
<br>
Modified: llvm/trunk/include/llvm/Support/SmallVectorMemoryBuffer.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/SmallVectorMemoryBuffer.h?rev=338175&r1=338174&r2=338175&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/SmallVectorMemoryBuffer.h?rev=338175&r1=338174&r2=338175&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/Support/SmallVectorMemoryBuffer.h (original)<br>
+++ llvm/trunk/include/llvm/Support/SmallVectorMemoryBuffer.h Fri Jul 27 16:12:11 2018<br>
@@ -49,6 +49,9 @@ public:<br>
     init(this->SV.begin(), this->SV.end(), false);<br>
   }<br>
<br>
+  // Key function.<br>
+  ~SmallVectorMemoryBuffer() override;<br>
+<br>
   StringRef getBufferIdentifier() const override { return BufferName; }<br>
<br>
   BufferKind getBufferKind() const override { return MemoryBuffer_Malloc; }<br>
@@ -56,7 +59,6 @@ public:<br>
 private:<br>
   SmallVector<char, 0> SV;<br>
   std::string BufferName;<br>
-  void anchor() override;<br>
 };<br>
<br>
 } // namespace llvm<br>
<br>
Modified: llvm/trunk/lib/Support/MemoryBuffer.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/MemoryBuffer.cpp?rev=338175&r1=338174&r2=338175&view=diff" rel="noreferrer" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/MemoryBuffer.cpp?rev=338175&r1=338174&r2=338175&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Support/MemoryBuffer.cpp (original)<br>
+++ llvm/trunk/lib/Support/MemoryBuffer.cpp Fri Jul 27 16:12:11 2018<br>
@@ -533,5 +533,4 @@ MemoryBufferRef MemoryBuffer::getMemBuff<br>
   return MemoryBufferRef(Data, Identifier);<br>
 }<br>
<br>
-void MemoryBuffer::anchor() {}<br>
-void SmallVectorMemoryBuffer::anchor() {}<br>
+SmallVectorMemoryBuffer::~SmallVectorMemoryBuffer() {}<br>
<br>
<br>
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</blockquote></div>