recommend using llvm-ar when finding undefined references and empty archives

Summary:
When we perform LTO builds with a version of ar that does not
understand LLVM bitcode objects, we end up with undefined references,
because our archive files do not list the bitcode symbols in their
indices. The error messages do not make it clear what the real problem
is. This change adds a note that points out the likely problem and
solution. It is similar in spirit to r282633, but aims to avoid false
positives by only triggering when we see both undefined references and
archives without symbols in their indices.

Fixes PR32281.

Reviewers: davide, ruiu, tejohnson

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31011

llvm-svn: 298124

llvm-svn: 298091

llvm-svn: 298072

Error was:
Relocations.cpp:792:38: error: expected primary-expression before ‘>’ token
         In<ELFT>::Iplt->addEntry<ELFT>(Body);

llvm-svn: 298070

Alternative approach can be remove templated method
either, like D31028 do.

llvm-svn: 298065

Was fixed, details on review page.

Original commit message:

That removes CopyRelSection class completely, making
Bss/BssRelRo to be just regular synthetics.

This is splitted from D30541 and polished.
Difference from D30541 that all logic of SharedSymbol
converting to DefinedRegular was removed for now and
probably will be posted as separate patch.

Differential revision: https://reviews.llvm.org/D30892

llvm-svn: 298062

That opens road to detemplate PltSection<ELFT>,
what allows then to detemplate all methods of SymbolBody.

llvm-svn: 297950

llvm-svn: 297942

llvm-svn: 297941

llvm-svn: 297939

llvm-svn: 297937

I suppose it is the reason of BB fail:
http://lab.llvm.org:8011/builders/clang-cmake-aarch64-lld/builds/921

https://bugs.llvm.org/show_bug.cgi?id=32167

llvm-svn: 297933

That removes CopyRelSection class completely, making
Bss/BssRelRo to be just regular synthetics.

This is splitted from D30541 and polished.
Difference from D30541 that all logic of SharedSymbol
converting to DefinedRegular was removed for now and
probably will be posted as separate patch.

Differential revision: https://reviews.llvm.org/D30892

llvm-svn: 297814

Being passed -z notext is a pretty strong indication that the user is
OK with text relocations. This is not the same behavior as bfd, but
bfd defaults to -z notext, so it has to try to avoid text relocations
and use them as a last resort.

llvm-svn: 297789

gold linker manual describes them as:

-z text	Do not permit relocations in read-only segments
-z notext Permit relocations in read-only segments (default)

In LLD default is to not permit them. Patch implements -z notext.

Differential revision: https://reviews.llvm.org/D30530

llvm-svn: 297366

This reverts commit r297008 because it's reported that that
change broke AArch64 bots.

llvm-svn: 297297

llvm-svn: 297287

    
This change moves the calls to finalizeContent() for each synthetic section
before createThunks(). This will allow us to assign addresses prior to
calling createThunks(). As addition of thunks may add to the static
symbol table and may affect the size of the mips got section we introduce a
couple of additional member functions to update these values.
    
Differential revision: https://reviews.llvm.org/D29983

llvm-svn: 297277

    
This change fixes a bug in which the Mips LA25 Thunks are always assigned
to the same Output section as the caller and not the callee as expected.

Differential Revision: https://reviews.llvm.org/D30637

llvm-svn: 297135

llvm-svn: 297107

llvm-svn: 297077

llvm-svn: 297012

In compare with D30458, this makes Bss/BssRelRo to be pure
synthetic sections.

That removes CopyRelSection class completely, making
Bss/BssRelRo to be just regular synthetics.

SharedSymbols involved in creating copy relocations are
converted to DefinedRegular, what also simplifies things.

Differential revision: https://reviews.llvm.org/D30541

llvm-svn: 297008

In many places we reset Size to 0 before calling assignOffsets()
manually. Sometimes we don't do that. 
It looks we can just always do that inside.

Previous code had:
template <class ELFT> void OutputSection::assignOffsets() {
  uint64_t Off = Size;

And tests feels fine with Off = 0. 
I think Off = Size make no sence.

Differential revision: https://reviews.llvm.org/D30463

llvm-svn: 296609

Differential Revision: https://reviews.llvm.org/D30348

llvm-svn: 296508

llvm-svn: 296307

Differential Revision: https://reviews.llvm.org/D30351

llvm-svn: 296303

Now that all special sections are SyntheticSections, we only need one
OutputSection class.

llvm-svn: 296127

With the current design an InputSection is basically anything that
goes directly in a OutputSection. That includes plain input section
but also synthetic sections, so this should probably not be a
template.

llvm-svn: 295993

We shouldn't report an error for R_*_NONE relocs since we're emitting
them when writing relocations to discarded sections.

Differential Revision: https://reviews.llvm.org/D30279

llvm-svn: 295936

Removing this template is not a big win by itself, but opens the way
for removing more templates.

llvm-svn: 295923

This option disable creating copy relocations. ld.bfd and ld.gold
have the same option.

llvm-svn: 295772

llvm-svn: 295632

llvm-svn: 295622

The previous name caused a little confusion because the function not
only returns aliases but a given symbol itself too.

llvm-svn: 295408

llvm-svn: 295289

llvm-svn: 295288

This patch removes NeedsCopyOrPltAddr and instead add two variables,
NeedsCopy and NeedsPltAddr. This uses one more bit in Symbol class,
but the actual size doesn't increase because we had unused bits.
This should improve code readability.

llvm-svn: 295287

This is slightly inefficient than the previous code, but that is really
negligible as this function is usually called at most only a few times.

llvm-svn: 295282

Previously, space in a BSS section for copy relocations are reserved
in a special way. We directly manipulated size of the BSS section.
r294577 changed the way of doing it. Now, we create an instance of
CopyRelSection (which is a synthetic input section) for each copy
relocation.

This patch removes the remains of the old way and add CopyRelSections
to BSS sections using `addSections` function, which is the usual
way to add an input section to an output section.

llvm-svn: 295278