[LLD][ELF] Fix stale comment about doing ICF

[russell.gallop]

Summary

Fix stale comment.

ICF is now done much further down (doIcf()).

[MaskRay]

lld/ELF/Driver.cpp

1918

merging of SHF_MERGE is not correct, either. The step is performed at sec->finalizeInputSections(); after D67504.

[russell.gallop]

Further fix comments.

[MaskRay]

lld/ELF/Driver.cpp

1919–1921

@peter.smith in case he has suggestions for the wording.

[peter.smith]

lld/ELF/Driver.cpp

1919–1921

I've got a minor suggestion, no strong opinions though.

I think it might be worth commenting separately about splitSections as it isn't obvious why it is where it is. Something like:

// Split SHF_MERGE and .eh_frame sections into pieces in preparation for garbage collection.
splitSections<ELFT>();
// Garbage collection and removal of unused shared objects from dependencies.
markLive<ELFT>();
demoteSharedSymbols();

[russell.gallop]

Thanks. I've used that wording. It describes the intent better.

[peter.smith]

Thanks for the update, I'm happy if Maskray is.

[MaskRay]

lld/ELF/Driver.cpp

1919–1921

not removal of unused shared objects

it is to change the symbol kind

[MaskRay]

lld/ELF/Driver.cpp

1919–1921

// Garbage collection and removal of shared symbols from unused shared objects.

[russell.gallop]

Pushed with MaskRay's latest wording. Thanks.

lld/ELF/Driver.cpp

template <class ELFT> void LinkerDriver::link(opt::InputArgList &args) {
 
   // This adds a .comment section containing a version string.
   if (!config->relocatable)
     inputSections.push_back(createCommentSection());
 
   // Replace common symbols with regular symbols.
   replaceCommonSymbols();
 
-  // Do size optimizations: garbage collection, merging of SHF_MERGE sections
-  // and identical code folding.
+  // Split SHF_MERGE and .eh_frame sections into pieces in preparation for garbage collection.
   splitSections<ELFT>();
+
+  // Garbage collection and removal of shared symbols from unused shared objects.
   markLive<ELFT>();
   demoteSharedSymbols();
 
   // Make copies of any input sections that need to be copied into each
   // partition.
   copySectionsIntoPartitions();
 
   // Create synthesized sections such as .got and .plt. This is called before