Instead of using std::copy, clear the vector first and add new elements. NFC.

[ruiu]

Summary

Instead of using std::copy, clear the vector first and add new elements. NFC.

[pcc]

LGTM

[dblaikie]

Out of curiosity - what was the motivation for this change? I'd expect that
copy would be faster than repeated push_back (though maybe LLVM can
optimize it to match)

lld/trunk/ELF/Writer.cpp

sortISDBySectionOrder(InputSectionDescription *ISD,
   // 16MB cold
   // 8MB hot
   // 16MB cold
   //
   // both the last 8-16MB of the first block of cold code and the first 8-16MB
   // of the second block of cold code can call the hot code without a thunk. So
   // we effectively double the amount of code that could potentially call into
   // the hot code without a thunk.
-  size_t UnorderedInsPt = 0;
+  size_t InsPt = 0;
   if (Target->ThunkSectionSpacing && !OrderedSections.empty()) {
     uint64_t UnorderedPos = 0;
-    for (; UnorderedInsPt != UnorderedSections.size(); ++UnorderedInsPt) {
-      UnorderedPos += UnorderedSections[UnorderedInsPt]->getSize();
+    for (; InsPt != UnorderedSections.size(); ++InsPt) {
+      UnorderedPos += UnorderedSections[InsPt]->getSize();
       if (UnorderedPos > UnorderedSize / 2)
         break;
     }
   }
 
-  std::copy(UnorderedSections.begin(),
-            UnorderedSections.begin() + UnorderedInsPt, ISD->Sections.begin());
-  std::vector<InputSection *>::iterator SectionsPos =
-      ISD->Sections.begin() + UnorderedInsPt;
+  ISD->Sections.clear();
+  for (InputSection *IS : makeArrayRef(UnorderedSections).slice(0, InsPt))
+    ISD->Sections.push_back(IS);
   for (std::pair<InputSection *, int> P : OrderedSections)
-    *SectionsPos++ = P.first;
-  std::copy(UnorderedSections.begin() + UnorderedInsPt, UnorderedSections.end(),
-            SectionsPos);
+    ISD->Sections.push_back(P.first);
+  for (InputSection *IS : makeArrayRef(UnorderedSections).slice(InsPt))
+    ISD->Sections.push_back(IS);
 }
 
 static void sortSection(OutputSection *Sec,
                         const DenseMap<const InputSectionBase *, int> &Order) {
   StringRef Name = Sec->Name;
 
   // Sort input sections by section name suffixes for
   // __attribute__((init_priority(N))).