Try to use gt/lt compares with 0 instead of class.

In the CoarrayChecker, add checks for the constraints C1177 and
C1178 for event-wait-stmt. Add event-post-stmt to the check
for the constraints for sync-stat-list. Add a check for the
constraint C1176 on event-variable.

Reviewed By: PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D137204

Reviewed By: #libc, philnik, Mordante

Spies: Mordante, philnik, libcxx-commits

Differential Revision: https://reviews.llvm.org/D148641

The source file is used to anchor the destructor of format_error. When
format is moved from experimental to stable this code would move to the
dylib. One issue with code in the dylib is that it can't be used in
constexpr context. There is a proposal to make format work during
constant evaluation

  P2758 Emitting messages at compile time

This paper has initially been received favourable by EWG. Therefore move
the code to the header. This also avoids possible availability issues on
Mac back deployment targets.

Note it is expected that format will no longer be experimental with the
next LLVM release.

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D150073

This was requested in the review of D145807, but I had missed to
apply it before landing the patch.

Differential Revision: https://reviews.llvm.org/D150444

Since CMake 3.20, CMake explicitly passes "-x c" (or equivalent)
when compiling a file which has been set as having the language
C. This behaviour change only takes place if "cmake_minimum_required"
is set to 3.20 or newer, or if the policy CMP0119 is set to new.

Attempting to compile assembly files with "-x c" fails, however
this is workarounded in many cases, as OpenMP overrides this with
"-x assembler-with-cpp", however this is only added for non-Windows
targets.

Thus, after increasing cmake_minimum_required to 3.20, this breaks
compiling the GNU assembly for Windows targets; the GNU assembly is
used for ARM and AArch64 Windows targets when building with Clang.
This patch unbreaks that.

Differential Revision: https://reviews.llvm.org/D150532

Reviewed in D148761; missed committing this before.

The build uses other mechanism to select the runtime.

Fixes #62719

Differential revision: https://reviews.llvm.org/D150688

Currently we use a template parameter called `InvertInbox` to invert the
inbox when we load it. This is more easily understood as a static check
on whether or not the process running it is the server. Inverting the
inbox makes the states 1 0 and 0 1 own the buffer, so it's easier to
simply say that the server own the buffer if in != out. Also clean up some of
the comments.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D150365

The S_LPROC32_ID and S_GPROC32_ID CodeView Debug Symbols have a flags
field which LLVM has had the values for (in the ProcSymFlags enum) but
has never actually set.

These flags are used by Microsoft-internal tooling that leverages debug
information to do binary analysis.

Modified LLVM to set the correct flags:

- ProcSymFlags::HasOptimizedDebugInfo - always set, as this indicates that
debug info is present for optimized builds (if debug info is not emitted
for optimized builds, then LLVM won't emit a debug symbol at all).
- ProcSymFlags::IsNoReturn and ProcSymFlags::IsNoInline - set if the
function has the NoReturn or NoInline attributes respectively.
- ProcSymFlags::HasFP - set if the function requires a frame pointer (per
TargetFrameLowering::hasFP).

Per discussion in review, XFAIL'ing lldb test until someone working on
lldb has a chance to look at it.

Differential Revision: https://reviews.llvm.org/D148761

Reviewed By: Peiming

Differential Revision: https://reviews.llvm.org/D150692

https://bugs.chromium.org/p/chromium/issues/detail?id=1445676

This reverts commit 1030bd18.

https://bugs.chromium.org/p/chromium/issues/detail?id=1445676

This reverts commit 20a3c6e8.

https://bugs.chromium.org/p/chromium/issues/detail?id=1445676

This reverts commit 6d7b26ae.

This reverts commit 9725c740.

Change the lowering of SVE integer mla_x/mls_x and mad_x/msb_x
builtins to use dedicated undef (_u) intrinsics.

Differential Revision: https://reviews.llvm.org/D150553

We were documenting that this was about recursive calls when it's
actually about arbitrary calls.

e.g., https://godbolt.org/z/en8sYd77E

Missed adding this check in previous commit so adding it through separate commit.

Reviewed By: raghavendhra

Differential Revision: https://reviews.llvm.org/D150626

This patch adds two versions of `bcmp` optimized for architectures where unaligned accesses are either illegal or extremely slow.
It is currently enabled for RISCV 64 and RISCV 32 but it could be used for ARM 32 architectures as well.

Here is the before / after output of `libc.benchmarks.memory_functions.opt_host --benchmark_filter=BM_memcmp` on a quad core Linux starfive RISCV 64 board running at 1.5GHz.

Before
```
Run on (4 X 1500 MHz CPU s)
CPU Caches:
  L1 Instruction 32 KiB (x4)
  L1 Data 32 KiB (x4)
  L2 Unified 2048 KiB (x1)
----------------------------------------------------------------------
Benchmark            Time             CPU   Iterations UserCounters...
----------------------------------------------------------------------
BM_Memcmp/0/0        110 ns         66.4 ns     10404864 bytes_per_cycle=0.107646/s bytes_per_second=153.989M/s items_per_second=15.071M/s __llvm_libc::memcmp,memcmp Google A
BM_Memcmp/1/0        318 ns          211 ns      3026944 bytes_per_cycle=0.131539/s bytes_per_second=188.167M/s items_per_second=4.73691M/s __llvm_libc::memcmp,memcmp Google B
BM_Memcmp/2/0        204 ns          115 ns      6118400 bytes_per_cycle=0.121675/s bytes_per_second=174.058M/s items_per_second=8.70241M/s __llvm_libc::memcmp,memcmp Google D
BM_Memcmp/3/0        143 ns         99.6 ns      7013376 bytes_per_cycle=0.117974/s bytes_per_second=168.763M/s items_per_second=10.0437M/s __llvm_libc::memcmp,memcmp Google L
BM_Memcmp/4/0       81.3 ns         58.2 ns     11426816 bytes_per_cycle=0.101125/s bytes_per_second=144.661M/s items_per_second=17.1805M/s __llvm_libc::memcmp,memcmp Google M
BM_Memcmp/5/0        177 ns          118 ns      5952512 bytes_per_cycle=0.120612/s bytes_per_second=172.537M/s items_per_second=8.45549M/s __llvm_libc::memcmp,memcmp Google Q
BM_Memcmp/6/0        342 ns          220 ns      3483648 bytes_per_cycle=0.132004/s bytes_per_second=188.834M/s items_per_second=4.54739M/s __llvm_libc::memcmp,memcmp Google S
BM_Memcmp/7/0        208 ns          130 ns      5681152 bytes_per_cycle=0.12468/s bytes_per_second=178.356M/s items_per_second=7.6674M/s __llvm_libc::memcmp,memcmp Google U
BM_Memcmp/8/0        123 ns         79.1 ns      8387584 bytes_per_cycle=0.110593/s bytes_per_second=158.204M/s items_per_second=12.6439M/s __llvm_libc::memcmp,memcmp Google W
BM_Memcmp/9/0      20707 ns        10643 ns        67584 bytes_per_cycle=0.142401/s bytes_per_second=203.707M/s items_per_second=93.9559k/s __llvm_libc::memcmp,uniform 384 to 4096
```

After
```
BM_Memcmp/0/0       80.4 ns         55.8 ns     12648448 bytes_per_cycle=0.132703/s bytes_per_second=189.834M/s items_per_second=17.9256M/s __llvm_libc::memcmp,memcmp Google A
BM_Memcmp/1/0        140 ns         80.5 ns      8230912 bytes_per_cycle=0.337273/s bytes_per_second=482.474M/s items_per_second=12.4165M/s __llvm_libc::memcmp,memcmp Google B
BM_Memcmp/2/0        101 ns         66.4 ns     10571776 bytes_per_cycle=0.208539/s bytes_per_second=298.317M/s items_per_second=15.0687M/s __llvm_libc::memcmp,memcmp Google D
BM_Memcmp/3/0        118 ns         67.6 ns     10533888 bytes_per_cycle=0.176822/s bytes_per_second=252.946M/s items_per_second=14.7946M/s __llvm_libc::memcmp,memcmp Google L
BM_Memcmp/4/0        106 ns         53.0 ns     12722176 bytes_per_cycle=0.111141/s bytes_per_second=158.988M/s items_per_second=18.8591M/s __llvm_libc::memcmp,memcmp Google M
BM_Memcmp/5/0        141 ns         70.2 ns     10436608 bytes_per_cycle=0.26032/s bytes_per_second=372.39M/s items_per_second=14.2458M/s __llvm_libc::memcmp,memcmp Google Q
BM_Memcmp/6/0        144 ns         79.3 ns      8932352 bytes_per_cycle=0.353168/s bytes_per_second=505.211M/s items_per_second=12.612M/s __llvm_libc::memcmp,memcmp Google S
BM_Memcmp/7/0        123 ns         71.7 ns      9945088 bytes_per_cycle=0.22143/s bytes_per_second=316.758M/s items_per_second=13.9421M/s __llvm_libc::memcmp,memcmp Google U
BM_Memcmp/8/0       97.0 ns         56.2 ns     12509184 bytes_per_cycle=0.160526/s bytes_per_second=229.635M/s items_per_second=17.7784M/s __llvm_libc::memcmp,memcmp Google W
BM_Memcmp/9/0       1840 ns          989 ns       676864 bytes_per_cycle=1.4894/s bytes_per_second=2.08067G/s items_per_second=1010.92k/s __llvm_libc::memcmp,uniform 384 to 4096
```

glibc
```
BM_Memcmp/0/0       72.6 ns         51.7 ns     12963840 bytes_per_cycle=0.141261/s bytes_per_second=202.075M/s items_per_second=19.3246M/s glibc::memcmp,memcmp Google A
BM_Memcmp/1/0        118 ns         75.2 ns      9280512 bytes_per_cycle=0.354054/s bytes_per_second=506.478M/s items_per_second=13.3046M/s glibc::memcmp,memcmp Google B
BM_Memcmp/2/0        114 ns         62.9 ns     11152384 bytes_per_cycle=0.222675/s bytes_per_second=318.539M/s items_per_second=15.8943M/s glibc::memcmp,memcmp Google D
BM_Memcmp/3/0       84.0 ns         63.5 ns     11030528 bytes_per_cycle=0.186353/s bytes_per_second=266.581M/s items_per_second=15.7378M/s glibc::memcmp,memcmp Google L
BM_Memcmp/4/0       93.5 ns         51.2 ns     13462528 bytes_per_cycle=0.119215/s bytes_per_second=170.539M/s items_per_second=19.5384M/s glibc::memcmp,memcmp Google M
BM_Memcmp/5/0        123 ns         61.7 ns     11376640 bytes_per_cycle=0.225262/s bytes_per_second=322.239M/s items_per_second=16.1993M/s glibc::memcmp,memcmp Google Q
BM_Memcmp/6/0        122 ns         71.6 ns      9967616 bytes_per_cycle=0.380844/s bytes_per_second=544.802M/s items_per_second=13.9579M/s glibc::memcmp,memcmp Google S
BM_Memcmp/7/0        118 ns         65.6 ns     10555392 bytes_per_cycle=0.238677/s bytes_per_second=341.43M/s items_per_second=15.2334M/s glibc::memcmp,memcmp Google U
BM_Memcmp/8/0       90.4 ns         54.0 ns     12920832 bytes_per_cycle=0.161987/s bytes_per_second=231.724M/s items_per_second=18.5169M/s glibc::memcmp,memcmp Google W
BM_Memcmp/9/0       1045 ns          601 ns      1195008 bytes_per_cycle=2.53677/s bytes_per_second=3.54383G/s items_per_second=1.66423M/s glibc::memcmp,uniform 384 to 4096
```

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D150663

m_name_list is a std::unordered_set<std::string>, we can insert the
string directly instead of grabbing the c_str and creating yet another
one.

This helps fix a regression from D148309 where a shift + add was no longer
combined into a ssra. It looks for add's with v1i64 extract operands and
converts them to v1i64 adds. The other operand needs to be something that is
easily converted to a v1i64, in this case it currently just checks for a load.

Some of the code in performAddSubCombine has been cleaned up whilst I was here.

Differential Revision: https://reviews.llvm.org/D148311

The right-hand sides of assignment statements are always expressions,
never variables.  When an assignment statement is converted into a call
to a defined assignment subroutine, and the actual argument being associated
with the second dummy argument is a variable, and the dummy argument does
not have the VALUE attribute, wrap it with parentheses so that lowering
will pass it by means of a temporary.

Fixes https://github.com/llvm/llvm-project/issues/62599.

Differential Revision: https://reviews.llvm.org/D150331

[libc] Add optimized bcmp for RISCV

This patch adds two versions of bcmp optimized for architectures where unaligned accesses are either illegal or extremely slow.
It is currently enabled for RISCV 64 and RISCV 32 but it could be used for ARM 32 architectures as well.

Here is the before / after output of libc.benchmarks.memory_functions.opt_host --benchmark_filter=BM_Bcmp on a quad core Linux starfive RISCV 64 board running at 1.5GHz.

Before
```
Run on (4 X 1500 MHz CPU s)
CPU Caches:
  L1 Instruction 32 KiB (x4)
  L1 Data 32 KiB (x4)
  L2 Unified 2048 KiB (x1)
Load Average: 7.03, 5.98, 3.71
----------------------------------------------------------------------
Benchmark            Time             CPU   Iterations UserCounters...
----------------------------------------------------------------------
BM_Bcmp/0/0        102 ns         60.5 ns     11662336 bytes_per_cycle=0.122696/s bytes_per_second=175.518M/s items_per_second=16.5258M/s __llvm_libc::bcmp,memcmp Google A
BM_Bcmp/1/0        328 ns          172 ns      3737600 bytes_per_cycle=0.15256/s bytes_per_second=218.238M/s items_per_second=5.80575M/s __llvm_libc::bcmp,memcmp Google B
BM_Bcmp/2/0        199 ns         99.7 ns      7019520 bytes_per_cycle=0.141897/s bytes_per_second=202.986M/s items_per_second=10.032M/s __llvm_libc::bcmp,memcmp Google D
BM_Bcmp/3/0        173 ns         86.5 ns      8361984 bytes_per_cycle=0.13863/s bytes_per_second=198.312M/s items_per_second=11.5669M/s __llvm_libc::bcmp,memcmp Google L
BM_Bcmp/4/0        105 ns         51.8 ns     13213696 bytes_per_cycle=0.116399/s bytes_per_second=166.51M/s items_per_second=19.2931M/s __llvm_libc::bcmp,memcmp Google M
BM_Bcmp/5/0        167 ns         93.9 ns      7853056 bytes_per_cycle=0.139432/s bytes_per_second=199.459M/s items_per_second=10.6503M/s __llvm_libc::bcmp,memcmp Google Q
BM_Bcmp/6/0        262 ns          165 ns      3931136 bytes_per_cycle=0.151516/s bytes_per_second=216.745M/s items_per_second=6.07091M/s __llvm_libc::bcmp,memcmp Google S
BM_Bcmp/7/0        168 ns          105 ns      6665216 bytes_per_cycle=0.143159/s bytes_per_second=204.791M/s items_per_second=9.52163M/s __llvm_libc::bcmp,memcmp Google U
BM_Bcmp/8/0        108 ns         68.0 ns     10175488 bytes_per_cycle=0.125504/s bytes_per_second=179.535M/s items_per_second=14.701M/s __llvm_libc::bcmp,memcmp Google W
BM_Bcmp/9/0      15371 ns         9007 ns        78848 bytes_per_cycle=0.166128/s bytes_per_second=237.648M/s items_per_second=111.031k/s __llvm_libc::bcmp,uniform 384 to 4096
```

After
```
BM_Bcmp/0/0       74.2 ns         49.7 ns     14306304 bytes_per_cycle=0.148927/s bytes_per_second=213.042M/s items_per_second=20.1101M/s __llvm_libc::bcmp,memcmp Google A
BM_Bcmp/1/0        108 ns         68.1 ns     10350592 bytes_per_cycle=0.411197/s bytes_per_second=588.222M/s items_per_second=14.6849M/s __llvm_libc::bcmp,memcmp Google B
BM_Bcmp/2/0       80.2 ns         56.0 ns     12386304 bytes_per_cycle=0.258588/s bytes_per_second=369.912M/s items_per_second=17.8585M/s __llvm_libc::bcmp,memcmp Google D
BM_Bcmp/3/0       92.4 ns         55.7 ns     12555264 bytes_per_cycle=0.206835/s bytes_per_second=295.88M/s items_per_second=17.943M/s __llvm_libc::bcmp,memcmp Google L
BM_Bcmp/4/0       79.3 ns         46.8 ns     14288896 bytes_per_cycle=0.125872/s bytes_per_second=180.061M/s items_per_second=21.3611M/s __llvm_libc::bcmp,memcmp Google M
BM_Bcmp/5/0       98.0 ns         57.9 ns     12232704 bytes_per_cycle=0.268815/s bytes_per_second=384.543M/s items_per_second=17.2711M/s __llvm_libc::bcmp,memcmp Google Q
BM_Bcmp/6/0        132 ns         65.5 ns     10474496 bytes_per_cycle=0.417246/s bytes_per_second=596.875M/s items_per_second=15.2673M/s __llvm_libc::bcmp,memcmp Google S
BM_Bcmp/7/0        101 ns         60.9 ns     11505664 bytes_per_cycle=0.253733/s bytes_per_second=362.968M/s items_per_second=16.4202M/s __llvm_libc::bcmp,memcmp Google U
BM_Bcmp/8/0       72.5 ns         50.2 ns     14082048 bytes_per_cycle=0.183262/s bytes_per_second=262.158M/s items_per_second=19.9271M/s __llvm_libc::bcmp,memcmp Google W
BM_Bcmp/9/0        852 ns          803 ns       854016 bytes_per_cycle=1.85028/s bytes_per_second=2.58481G/s items_per_second=1.24597M/s __llvm_libc::bcmp,uniform 384 to 4096
```

For comparison with glibc
```
BM_Bcmp/0/0        106 ns         52.6 ns     12906496 bytes_per_cycle=0.142072/s bytes_per_second=203.235M/s items_per_second=19.0271M/s glibc::bcmp,memcmp Google A
BM_Bcmp/1/0        132 ns         77.1 ns      8905728 bytes_per_cycle=0.365072/s bytes_per_second=522.239M/s items_per_second=12.9782M/s glibc::bcmp,memcmp Google B
BM_Bcmp/2/0        122 ns         62.3 ns     10909696 bytes_per_cycle=0.222667/s bytes_per_second=318.527M/s items_per_second=16.0563M/s glibc::bcmp,memcmp Google D
BM_Bcmp/3/0       99.5 ns         64.2 ns     11074560 bytes_per_cycle=0.185126/s bytes_per_second=264.825M/s items_per_second=15.5674M/s glibc::bcmp,memcmp Google L
BM_Bcmp/4/0       86.6 ns         50.2 ns     13488128 bytes_per_cycle=0.117941/s bytes_per_second=168.717M/s items_per_second=19.9053M/s glibc::bcmp,memcmp Google M
BM_Bcmp/5/0        106 ns         61.4 ns     11344896 bytes_per_cycle=0.248968/s bytes_per_second=356.151M/s items_per_second=16.284M/s glibc::bcmp,memcmp Google Q
BM_Bcmp/6/0        145 ns         71.9 ns     10046464 bytes_per_cycle=0.389814/s bytes_per_second=557.633M/s items_per_second=13.9019M/s glibc::bcmp,memcmp Google S
BM_Bcmp/7/0        119 ns         65.6 ns     10718208 bytes_per_cycle=0.243756/s bytes_per_second=348.696M/s items_per_second=15.2329M/s glibc::bcmp,memcmp Google U
BM_Bcmp/8/0       86.4 ns         54.5 ns     13250560 bytes_per_cycle=0.154831/s bytes_per_second=221.488M/s items_per_second=18.3532M/s glibc::bcmp,memcmp Google W
BM_Bcmp/9/0       1090 ns          604 ns      1186816 bytes_per_cycle=2.53848/s bytes_per_second=3.54622G/s items_per_second=1.65598M/s glibc::bcmp,uniform 384 to 4096
```

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D150567

This patch adds handling of DW_OP_addrx and DW_OP_constx expression operands.
In --update case these operands are preserved as is. Otherwise they are
converted into the DW_OP_addr and DW_OP_const[*]u correspondingly.

Differential Revision: https://reviews.llvm.org/D147066

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D150680

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D150682

Reviewed By: aartbik

Differential Revision: https://reviews.llvm.org/D150477

Apply the default PUBLIC/PRIVATE accessibility of a module to its symbols
a second time after it is known that all symbols, including implicitly typed
names from NAMELIST groups and specification expressions in module subprograms,
have been created in its scope.

Fixes https://github.com/llvm/llvm-project/issues/62598.

Differential Revision: https://reviews.llvm.org/D150307

This patch migrates uses of StringRef::{starts,ends}with_insensitive
to StringRef::{starts,ends}_with_insensitive so that we can use names
similar to those used in std::string_view.

Note that the llvm/ directory has migrated in commit
6c3ea866.

I'll post a separate patch to deprecate
StringRef::{starts,ends}with_insensitive.

Differential Revision: https://reviews.llvm.org/D150506

Instead of checking arch version, check HVX version when dealing with
HVX instructions.

After tokenizing an identifier, don't allow the next token to be a
Hollerith literal.

Fixes https://github.com/llvm/llvm-project/issues/58732.

Differential Revision: https://reviews.llvm.org/D150406

[Clang][Flang][OpenMP] Add loadOffloadInfoMetadata and createOffloadEntriesAndInfoMetadata into OMPIRBuilder's finalize and initialize

This allows the generation of OpenMP offload metadata for the OpenMP
dialect when lowering to LLVM-IR and moves some of the shared logic
between the OpenMP Dialect and Clang into the IRBuilder.

Reviewers: jsjodin, jdoerfert, kiranchandramohan

Differential Revision: https://reviews.llvm.org/D148370

The two constants should be equal only if their derived types
are the same. This fixes regression caused by D150380.

Differential Revision: https://reviews.llvm.org/D150634

Previously we added the SP operands when an immediate operand was added
to certain opcodes.

This patch moves it to a post processing step using the information
in MCInstrDesc. This avoids an explicit opcode list in RISCVDisassembler.cpp.

In considered using a custom DecoderMethod, but the bit swizzling we
need to do for the immediates on these instructions made that
unattractive.

Reviewed By: asb

Differential Revision: https://reviews.llvm.org/D149931

Whether assertions are enabled or not is orthogonal to the build type
which could lead to surprising behavior for lldbassert. Previously, when
doing a debug build with assertions disabled, lldbassert would become a
NOOP, rather than printing an error like it does in a release build. By
definining lldbassert in terms of NDEBUG, it behaves like a regular
assert when assertions are enabled, and like a soft assert.

Differential revision: https://reviews.llvm.org/D150639

If a symbol needs both JUMP_SLOT and GLOB_DAT relocations, there is a
minor linker optimization to keep just GLOB_DAT. This optimization
is only implemented by GNU ld's x86 port and mold.
https://maskray.me/blog/2021-08-29-all-about-global-offset-table#combining-.got-and-.got.plt

With the optimizing, the PLT entry is placed in .plt.got and the
associated GOTPLT entry is placed in .got (ld.bfd -z now) or .got.plt (ld.bfd -z lazy).
The relocation is in .rel[a].dyn.

This patch synthesizes `symbol@plt` labels for these .plt.got entries.

Example:
```
cat > a.s <<e
.globl _start; _start:
mov combined0@gotpcrel(%rip), %rax; mov combined1@gotpcrel(%rip), %rax
call combined0@plt; call combined1@plt
call foo0@plt; call foo1@plt
e
cat > b.s <<e
.globl foo0, foo1, combined0, combined1
foo0: foo1: combined0: combined1:
e
gcc -fuse-ld=bfd -shared b.s -o b.so
gcc -fuse-ld=bfd -pie -nostdlib a.s b.so -o a
```

```
Disassembly of section .plt:

0000000000001000 <.plt>:
    1000: ff 35 ea 1f 00 00             pushq   0x1fea(%rip)            # 0x2ff0 <_GLOBAL_OFFSET_TABLE_+0x8>
    1006: ff 25 ec 1f 00 00             jmpq    *0x1fec(%rip)           # 0x2ff8 <_GLOBAL_OFFSET_TABLE_+0x10>
    100c: 0f 1f 40 00                   nopl    (%rax)

0000000000001010 <foo1@plt>:
    1010: ff 25 ea 1f 00 00             jmpq    *0x1fea(%rip)           # 0x3000 <_GLOBAL_OFFSET_TABLE_+0x18>
    1016: 68 00 00 00 00                pushq   $0x0
    101b: e9 e0 ff ff ff                jmp     0x1000 <.plt>

0000000000001020 <foo0@plt>:
    1020: ff 25 e2 1f 00 00             jmpq    *0x1fe2(%rip)           # 0x3008 <_GLOBAL_OFFSET_TABLE_+0x20>
    1026: 68 01 00 00 00                pushq   $0x1
    102b: e9 d0 ff ff ff                jmp     0x1000 <.plt>

Disassembly of section .plt.got:

0000000000001030 <combined0@plt>:
    1030: ff 25 a2 1f 00 00             jmpq    *0x1fa2(%rip)           # 0x2fd8 <foo1+0x2fd8>
    1036: 66 90                         nop

0000000000001038 <combined1@plt>:
    1038: ff 25 a2 1f 00 00             jmpq    *0x1fa2(%rip)           # 0x2fe0 <foo1+0x2fe0>
    103e: 66 90                         nop
```

For x86-32, with -z now, if we remove `foo0` and `foo1`, the absence of regular
PLT will cause GNU ld to omit .got.plt, and our code cannot synthesize @plt
labels. This is an extreme corner case that almost never happens in practice (to
trigger the case, ensure every PLT symbol has been taken address). To fix it, we
can get the `_GLOBAL_OFFSET_TABLE_` symbol value, but the complexity is not
worth it.

Close https://github.com/llvm/llvm-project/issues/62537

Reviewed By: bd1976llvm

Differential Revision: https://reviews.llvm.org/D149817