[ELF] mergeCmp: work around irreflexivity bug

Some tests (e.g. aarch64-feature-pac.s) segfault in libstdc++ _GLIBCXX_DEBUG
builds (enabled by LLVM_ENABLE_EXPENSIVE_CHECKS).

dyn_cast<ThunkSection> i

[ELF] mergeCmp: work around irreflexivity bug

Some tests (e.g. aarch64-feature-pac.s) segfault in libstdc++ _GLIBCXX_DEBUG
builds (enabled by LLVM_ENABLE_EXPENSIVE_CHECKS).

dyn_cast<ThunkSection> is incorrectly true for any SyntheticSection. std::merge
transitively calls mergeCmp(x, x) (due to __glibcxx_requires_irreflexive_pred)
and will segfault in `ta->getTargetInputSection()`. The dyn_cast<ThunkSection>
issue should be eventually fixed properly, bug `a != b` is robust enough for now.

(cherry picked from commit abd9807590fc10eb92eb22aea7b50dbf08db7e9d)

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[ELF] Relax R_RISCV_ALIGN

Alternative to D125036. Implement R_RISCV_ALIGN relaxation so that we can handle
-mrelax object files (i.e. -mno-relax is no longer needed) and creates a
framework for futu

[ELF] Relax R_RISCV_ALIGN

Alternative to D125036. Implement R_RISCV_ALIGN relaxation so that we can handle
-mrelax object files (i.e. -mno-relax is no longer needed) and creates a
framework for future relaxation.

`relaxAux` is placed in a union with InputSectionBase::jumpInstrMod, storing
auxiliary information for relaxation. In the first pass, `relaxAux` is allocated.
The main data structure is `relocDeltas`: when referencing `relocations[i]`, the
actual offset is `r_offset - (i ? relocDeltas[i-1] : 0)`.

`relaxOnce` performs one relaxation pass. It computes `relocDeltas` for all text
section. Then, adjust st_value/st_size for symbols relative to this section
based on `SymbolAnchor`. `bytesDropped` is set so that `assignAddresses` knows
that the size has changed.

Run `relaxOnce` in the `finalizeAddressDependentContent` loop to wait for
convergence of text sections and other address dependent sections (e.g.
SHT_RELR). Note: extrating `relaxOnce` into a separate loop works for many cases
but has issues in some linker script edge cases.

After convergence, compute section contents: shrink the NOP sequence of each
R_RISCV_ALIGN as appropriate. Instead of deleting bytes, we run a sequence of
memcpy on the content delimitered by relocation locations. For R_RISCV_ALIGN let
the next memcpy skip the desired number of bytes. Section content computation is
parallelizable, but let's ensure the implementation is mature before
optimizations. Technically we can save a copy if we interleave some code with
`OutputSection::writeTo`, but let's not pollute the generic code (we don't have
templated relocation resolving, so using conditions can impose overhead to
non-RISCV.)

Tested:
`make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- LLVM=1 defconfig all` built Linux kernel using -mrelax is bootable.
FreeBSD RISCV64 system using -mrelax is bootable.
bash/curl/firefox/libevent/vim/tmux using -mrelax works.

Differential Revision: https://reviews.llvm.org/D127581

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

Reland "[lld-macho] Group undefined symbol diagnostics by symbol".

This reverts commit 36e7c9a450db5e22af1ec21412d918ceb2313942.

This relands d61341768cf0cff7c with the fix described in
https://rev

Reland "[lld-macho] Group undefined symbol diagnostics by symbol".

This reverts commit 36e7c9a450db5e22af1ec21412d918ceb2313942.

This relands d61341768cf0cff7c with the fix described in
https://reviews.llvm.org/D127753#3587390

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[lld] Fix typo for processAux; NFC

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D125163

[ELF] Fix branch range computation when picking ThunkSection

Similar to D117734. Take AArch64 as an example when the branch range is +-0x8000000.

getISDThunkSec returns `ts` when `src-0x8000000-r_a

[ELF] Fix branch range computation when picking ThunkSection

Similar to D117734. Take AArch64 as an example when the branch range is +-0x8000000.

getISDThunkSec returns `ts` when `src-0x8000000-r_addend <= tsBase < src-0x8000000`
and the new thunk will be placed in `ts` (`ts->addThunk(t)`). However, the new
thunk (at the end of ts) may be unreachable from src. In the next pass,
`normalizeExistingThunk` reverts the relocation back to the original target.
Then a new thunk is created and the same `ts` is picked as before. The `ts` is
still unreachable.

I have observed it in one test with a sufficiently large r_addend (47664): there
are initially 245 Thunk's, then in each pass 14 new Thunk's are created and get
appended to the unreachable ThunkSection. After 15 passes lld fails with
`thunk creation not converged`.

The new test aarch64-thunk-reuse2.s checks the case.

Without `- pcBias`, arm-thumb-thunk-empty-pass.s and arm-thunk-multipass-plt.s
will fail.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D124653

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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
* 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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[ELF] Simplify addCopyRelSymbol with invokeELFT. NFC

[ELF] Don't rely on Symbols.h's transitive inclusion of InputFiles.h. NFC

[ELF] Remove SharedSymbol::getFile. NFC

Symbol.h depends on InputFiles.h. This change moves us toward dropping the
weird dependency.

The call sites will become slightly uglier (`cast<SharedFile>(s-

[ELF] Remove SharedSymbol::getFile. NFC

Symbol.h depends on InputFiles.h. This change moves us toward dropping the
weird dependency.

The call sites will become slightly uglier (`cast<SharedFile>(s->file)`), but
the compromise is acceptable.

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[ELF] Replace uncompressed InputSectionBase::data() with rawData. NFC

In many call sites we know uncompression cannot happen (non-SHF_ALLOC, or the
data (even if compressed) must have been uncompres

[ELF] Replace uncompressed InputSectionBase::data() with rawData. NFC

In many call sites we know uncompression cannot happen (non-SHF_ALLOC, or the
data (even if compressed) must have been uncompressed by a previous pass).
Prefer rawData in these cases. data() increases code size and prevents
optimization on rawData.

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[ELF] Clean up headers. NFC

[ELF] Move Symbol::needsTlsLd to config->needsTlsLd

to decrease sizeof(SymbolUnion) from 72 to 64 on ELF64 platforms.

Use a dummy `Undefined` to prevent null pointer dereference (though unused)
`*r

[ELF] Move Symbol::needsTlsLd to config->needsTlsLd

to decrease sizeof(SymbolUnion) from 72 to 64 on ELF64 platforms.

Use a dummy `Undefined` to prevent null pointer dereference (though unused)
`*rel.sym` in InputSectionBase::relocateAlloc.

The relocation order may shuffle a bit, but otherwise there is no behavior
difference.

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Revert "[ELF] Move Symbol::needsTlsLd to config->needsTlsLd. NFC"

This reverts commit f9e3ca542ec17a0aa706bb51dcddf7fc6f0988ac.

The commit results in internal test failures. Test case provided offl

Revert "[ELF] Move Symbol::needsTlsLd to config->needsTlsLd. NFC"

This reverts commit f9e3ca542ec17a0aa706bb51dcddf7fc6f0988ac.

The commit results in internal test failures. Test case provided offline.

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[ELF] Symbol::replace: use the old nameData/nameSize. NFC

Currently `this->getName() == newSym.getName()`.
By keeping the old nameData/nameSize, newSym's nameData/nameSize will be
ignored. The call

[ELF] Symbol::replace: use the old nameData/nameSize. NFC

Currently `this->getName() == newSym.getName()`.
By keeping the old nameData/nameSize, newSym's nameData/nameSize will be
ignored. The call sites can avoid calling getName().

printTraceSymbol needs to take the symbol name since `other`'s name is empty.

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[ELF] De-template reportUndefinedSymbols. NFC

My x86-64 lld executable is 16KiB smaller.

[ELF] Move Symbol::needsTlsLd to config->needsTlsLd. NFC

to decrease sizeof(SymbolUnion) from 72 to 64 on ELF64 platforms.

[ELF] Fix the branch range computation when reusing a thunk

Notation: dst is `t->getThunkTargetSym()->getVA()`

On AArch64, when `src-0x8000000-r_addend <= dst < src-0x8000000`, the condition
`targe

[ELF] Fix the branch range computation when reusing a thunk

Notation: dst is `t->getThunkTargetSym()->getVA()`

On AArch64, when `src-0x8000000-r_addend <= dst < src-0x8000000`, the condition
`target->inBranchRange(rel.type, src, rel.sym->getVA(rel.addend))` may
incorrectly consider a thunk reusable.
`rel.addend = -getPCBias(rel.type)` resets the addend to 0 for AArch64/PPC
and the zero addend is used by `rel.sym->getVA(rel.addend)` to check
out-of-range relocations.

See the test for a case this computation is wrong:
`error: a.o:(.text_high+0x4): relocation R_AARCH64_JUMP26 out of range: -134217732 is not in [-134217728, 134217727]`
I have seen a real world case with r_addend=19960.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D117734

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[ELF] RelocationScanner::scanOne: replace rel.r_offset with offset. NFC

[ELF] Relocations: remove some cast<Undefined>. NFC

[ELF] De-template getAlternativeSpelling. NFC

[ELF] Add RelocationScanner. NFC

Currently the way some relocation-related static functions pass around
states is clumsy. Add a Resolver class to store some states as member
variables.

Advantages:

[ELF] Add RelocationScanner. NFC

Currently the way some relocation-related static functions pass around
states is clumsy. Add a Resolver class to store some states as member
variables.

Advantages:

* Avoid the parameter `InputSectionBase &sec` (this offsets the cost passing around `this` paramemter)
* Avoid the parameter `end` (Mips and PowerPC hacks)
* `config` and `target` can be cached as member variables to reduce global state accesses. (potential speedup because the compiler didn't know `config`/`target` were not changed across function calls)
* If we ever want to reduce if-else costs (e.g. `config->emachine==EM_MIPS` for non-Mips) or introduce parallel relocation scan not handling some tricky arches (PPC/Mips), we can templatize Resolver

`target` isn't used as much as `config`, so I change it to a const reference
during the migration.

There is a minor performance inprovement for elf::scanRelocations.

Reviewed By: ikudrin, peter.smith

Differential Revision: https://reviews.llvm.org/D116881

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[ELF] Move OffsetGetter before some static functions. NFC

to prepare for D116881.