[ELF] Suppress "duplicate symbol" when resolving STB_WEAK and STB_GNU_UNIQUE in different COMDATs

```
template <typename T> struct A {
A() {}
int value = 0;
};

template <typename Value> struct

[ELF] Suppress "duplicate symbol" when resolving STB_WEAK and STB_GNU_UNIQUE in different COMDATs

```
template <typename T> struct A {
A() {}
int value = 0;
};

template <typename Value> struct B {
static A<int> a;
};

template <typename Value> A<int> B<Value>::a;

inline int foo() {
return B<int>::a.value;
}
```

```
clang++ -c -fno-pic a.cc -o weak.o
g++ -c -fno-pic a.cc -o unique.o # --enable-gnu-unique-object

# Duplicate symbol error. In postParse, we do not check `sym.binding`
ld.lld -e 0 weak.o unique.o
```

Mixing GCC and Clang object files in this case is not ideal. .bss._ZGVN1BIiE1aE
has different COMDAT groups. It appears to work in practice because the guard
variable prevents harm due to double initialization.

For the linker, we just stick with the rule that a weak binding does not cause
"duplicate symbol" errors.

Close https://github.com/llvm/llvm-project/issues/58232

Differential Revision: https://reviews.llvm.org/D136381

(cherry picked from commit 0051b6bb78772b0658f28e5f31ddf91c1589aab5)

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[ELF] addDependentLibrary: fix a use-after-free bug in archiveName

[ELF] --fortran-common: remove unneeded identify_magic call. NFC

[ELF] Simplify createObjectFile/createLazyFile. NFC

And avoid redundant identify_magic test.

Use value instead of getValue (NFC)

[ELF] Move InputFiles global variables (memoryBuffers, objectFiles, etc) into Ctx. NFC

[lld] Don't use Optional::hasValue (NFC)

This patch replaces x.hasValue() with x where x is contextually
convertible to bool.

Revert "Don't use Optional::hasValue (NFC)"

This reverts commit aa8feeefd3ac6c78ee8f67bf033976fc7d68bc6d.

Don't use Optional::hasValue (NFC)

Reland "[lld-macho] Show source information for undefined references"

The error used to look like this:

ld64.lld: error: undefined symbol: _foo
>>> referenced by /path/to/bar.o:(symbol _baz+0x4

Reland "[lld-macho] Show source information for undefined references"

The error used to look like this:

ld64.lld: error: undefined symbol: _foo
>>> referenced by /path/to/bar.o:(symbol _baz+0x4)

If DWARF line information is available, we now show where in the source
the references are coming from:

ld64.lld: error: unreferenced symbol: _foo
>>> referenced by: bar.cpp:42 (/path/to/bar.cpp:42)
>>> /path/to/bar.o:(symbol _baz+0x4)

The reland is identical to the first time this landed. The fix was in D128294.
This reverts commit 0cc7ad417585b3185c32e395cc5e6cf082a347af.

Differential Revision: https://reviews.llvm.org/D128184

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Don't use Optional::getValue (NFC)

Revert "[lld-macho] Show source information for undefined references"

This reverts commit cd7624f15369f0d395c1edee1a0b9592083d2fe0.
See https://reviews.llvm.org/D128184#3597534

[lld-macho] Show source information for undefined references

The error used to look like this:

ld64.lld: error: undefined symbol: _foo
>>> referenced by /path/to/bar.o:(symbol _baz+0x4)

If DWA

[lld-macho] Show source information for undefined references

The error used to look like this:

ld64.lld: error: undefined symbol: _foo
>>> referenced by /path/to/bar.o:(symbol _baz+0x4)

If DWARF line information is available, we now show where in the source
the references are coming from:

ld64.lld: error: unreferenced symbol: _foo
>>> referenced by: bar.cpp:42 (/path/to/bar.cpp:42)
>>> /path/to/bar.o:(symbol _baz+0x4)

Differential Revision: https://reviews.llvm.org/D128184

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Don't use Optional::hasValue (NFC)

[ELF] Move invalid binding diagnostic from initializeSymbols to postParse

It is excessive to have a diagnostic for STB_LOCAL. Just reuse the invalid
binding diagnostic for STB_LOCAL.

[ELF] Optimize "Strip sections"

If SHT_LLVM_SYMPART is unused, don't iterate over inputSections.
If neither --strip-debug/--strip-all, don't iterate over inputSections.

[ELF] Move section assignment from initializeSymbols to postParse

https://discourse.llvm.org/t/parallel-input-file-parsing/60164

initializeSymbols currently sets Defined::section and handles non-pr

[ELF] Move section assignment from initializeSymbols to postParse

https://discourse.llvm.org/t/parallel-input-file-parsing/60164

initializeSymbols currently sets Defined::section and handles non-prevailing
COMDAT groups. Move the code to the parallel postParse to reduce work from the
single-threading code path and make parallel section initialization infeasible.

Postpone reporting duplicate symbol errors so that the messages have the
section information. (`Defined::section` is assigned in postParse and another
thread may not have the information).

* duplicated-synthetic-sym.s: BinaryFile duplicate definition (very rare) now
has no section information
* comdat-binding: `%t/w.o %t/g.o` leads to an undesired undefined symbol. This
is not ideal but we report a diagnostic to inform that this is unsupported.
(See release note)
* comdat-discarded-lazy.s: %tdef.o is unextracted. The new behavior (discarded
section error) makes more sense
* i386-comdat.s: switched to a better approach working around
.gnu.linkonce.t.__x86.get_pc_thunk.bx in glibc<2.32 for x86-32.
Drop the ancient no-longer-relevant workaround for __i686.get_pc_thunk.bx

Depends on D120640

Differential Revision: https://reviews.llvm.org/D120626

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Revert D120626 "[ELF] Move section assignment from initializeSymbols to postParse"

This reverts commit c30e6447c0225f675773d07f2b6d4e3c2b962155.
It exposed brittle support for __x86.get_pc_thunk.bx.

Revert D120626 "[ELF] Move section assignment from initializeSymbols to postParse"

This reverts commit c30e6447c0225f675773d07f2b6d4e3c2b962155.
It exposed brittle support for __x86.get_pc_thunk.bx.
Need to think a bit how to support __x86.get_pc_thunk.bx.

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[ELF] Move section assignment from initializeSymbols to postParse

https://discourse.llvm.org/t/parallel-input-file-parsing/60164

initializeSymbols currently sets Defined::section and handles non-pr

[ELF] Move section assignment from initializeSymbols to postParse

https://discourse.llvm.org/t/parallel-input-file-parsing/60164

initializeSymbols currently sets Defined::section and handles non-prevailing
COMDAT groups. Move the code to the parallel postParse to reduce work from the
single-threading code path and make parallel section initialization infeasible.

Postpone reporting duplicate symbol errors so that the messages have the
section information. (`Defined::section` is assigned in postParse and another
thread may not have the information).

* duplicated-synthetic-sym.s: BinaryFile duplicate definition (very rare) now
has no section information
* comdat-binding: `%t/w.o %t/g.o` leads to an undesired undefined symbol. This
is not ideal but we report a diagnostic to inform that this is unsupported.
(See release note)
* comdat-discarded-lazy.s: %tdef.o is unextracted. The new behavior (discarded
section error) makes more sense

Depends on D120640

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D120626

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Reland D119909 [ELF] Parallelize initializeLocalSymbols

ObjFile::parse combines symbol initialization and resolution. Many tasks
unrelated to symbol resolution can be postponed and parallelized. Thi

Reland D119909 [ELF] Parallelize initializeLocalSymbols

ObjFile::parse combines symbol initialization and resolution. Many tasks
unrelated to symbol resolution can be postponed and parallelized. This patch
extracts local symbol initialization and parallelizes it.

Technically the new function initializeLocalSymbols can be merged into
ObjFile::postParse, but functions like getSrcMsg may access the
uninitialized (all nullptr) local part of InputFile::symbols.

Linking chrome: 1.02x as fast with glibc malloc, 1.04x as fast with mimalloc

Depends on f456c3ae3f4182b23673929e8fe0aa18bcec4289 and D119908

Reviewed By: ikudrin

Differential Revision: https://reviews.llvm.org/D119909

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Revert "[ELF] Parallelize initializeLocalSymbols"

This reverts commit 09602d3b47ec83abb2c26efa5a199c13b72c7abf.

[ELF] BitcodeFile: resolve defined symbols before undefined symbols

This ports D95985 for ELF relocatable object files to BitcodeFile.

[ELF] Parallelize initializeLocalSymbols

ObjFile::parse combines symbol initialization and resolution. Many tasks
unrelated to symbol resolution can be postponed and parallelized. This patch
extract

[ELF] Parallelize initializeLocalSymbols

ObjFile::parse combines symbol initialization and resolution. Many tasks
unrelated to symbol resolution can be postponed and parallelized. This patch
extracts local symbol initialization and parallelizes it.

Technically the new function initializeLocalSymbols can be merged into
ObjFile::postParse, but functions like getSrcMsg may access the
uninitialized (all nullptr) local part of InputFile::symbols.

Linking chrome: 1.02x as fast with glibc malloc, 1.04x as fast with mimalloc

Reviewed By: ikudrin

Differential Revision: https://reviews.llvm.org/D119909

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[ELF] Move isUsedInRegularObj assignment from ctor to call sites. NFC

This removes the tricky
`isUsedInRegularObj(!file || file->kind() == InputFile::ObjKind)`
and the copy from `Symbol::mergeProper

[ELF] Move isUsedInRegularObj assignment from ctor to call sites. NFC

This removes the tricky
`isUsedInRegularObj(!file || file->kind() == InputFile::ObjKind)`
and the copy from `Symbol::mergeProperties`.

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[ELF] Move TLS mismatch error from Symbol::replace to postParse

* detect `def_tls.o undef_nontls.o` violation
* place error checking code (checking duplicate symbol) together
* allow `--defsym tls1=

[ELF] Move TLS mismatch error from Symbol::replace to postParse

* detect `def_tls.o undef_nontls.o` violation
* place error checking code (checking duplicate symbol) together
* allow `--defsym tls1=tls2 def_tls.o`

As a degraded error checking, `--defsym tls1=42` violation will not be detected.

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