Revert D126950 "[lld][WebAssembly] Retain data segments referenced via __start/__stop"

This reverts commit dcf3368e33c3a01bd21b692d3be5dc1ecee587f4.

It breaks -DLLVM_ENABLE_ASSERTIONS=on builds. In

Revert D126950 "[lld][WebAssembly] Retain data segments referenced via __start/__stop"

This reverts commit dcf3368e33c3a01bd21b692d3be5dc1ecee587f4.

It breaks -DLLVM_ENABLE_ASSERTIONS=on builds. In addition, the description is
incorrect about ld.lld behavior. For wasm, there should be justification to add
the new mode.

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[lld][WebAssembly] Retain data segments referenced via __start/__stop

As well as ELF linker does, retain all data segments named X referenced
through `__start_X` or `__stop_X`.

For example, `FOO_MD

[lld][WebAssembly] Retain data segments referenced via __start/__stop

As well as ELF linker does, retain all data segments named X referenced
through `__start_X` or `__stop_X`.

For example, `FOO_MD` should not be stripped in the below case, but it's currently mis-stripped

```llvm
@FOO_MD = global [4 x i8] c"bar\00", section "foo_md", align 1
@__start_foo_md = external constant i8*
@__stop_foo_md = external constant i8*
@llvm.used = appending global [1 x i8*] [i8* bitcast (i32 ()* @foo_md_size to i8*)], section "llvm.metadata"

define i32 @foo_md_size() {
entry:
ret i32 sub (
i32 ptrtoint (i8** @__stop_foo_md to i32),
i32 ptrtoint (i8** @__start_foo_md to i32)
)
}
```

This fixes https://github.com/llvm/llvm-project/issues/55839

Reviewed By: sbc100

Differential Revision: https://reviews.llvm.org/D126950

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[WebAssembly] Rename event to tag

We recently decided to change 'event' to 'tag', and 'event section' to
'tag section', out of the rationale that the section contains a
generalized tag that referenc

[WebAssembly] Rename event to tag

We recently decided to change 'event' to 'tag', and 'event section' to
'tag section', out of the rationale that the section contains a
generalized tag that references a type, which may be used for something
other than exceptions, and the name 'event' can be confusing in the web
context.

See
- https://github.com/WebAssembly/exception-handling/issues/159#issuecomment-857910130
- https://github.com/WebAssembly/exception-handling/pull/161

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D104423

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[lld][WebAssembly] Common superclass for input globals/events/tables

This commit regroups commonalities among InputGlobal, InputEvent, and
InputTable into the new InputElement. The subclasses are d

[lld][WebAssembly] Common superclass for input globals/events/tables

This commit regroups commonalities among InputGlobal, InputEvent, and
InputTable into the new InputElement. The subclasses are defined
inline in the new InputElement.h. NFC.

Reviewed By: sbc100

Differential Revision: https://reviews.llvm.org/D94677

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[lld][WebAssembly] Update comments mentioning legacy function names. NFC

The __wasm_apply_relocs function was split into two separate
functions as part of https://reviews.llvm.org/D93066 but these
c

[lld][WebAssembly] Update comments mentioning legacy function names. NFC

The __wasm_apply_relocs function was split into two separate
functions as part of https://reviews.llvm.org/D93066 but these
comments were not correctly updated at the time.

Differential Revision: https://reviews.llvm.org/D95623

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[WebAssembly] Add support for table linking to wasm-ld

This patch adds support to wasm-ld for linking multiple table references
together, in a manner similar to wasm globals. The indirect function
t

[WebAssembly] Add support for table linking to wasm-ld

This patch adds support to wasm-ld for linking multiple table references
together, in a manner similar to wasm globals. The indirect function
table is synthesized as needed.

To manage the transitional period in which the compiler doesn't yet
produce TABLE_NUMBER relocations and doesn't residualize table symbols,
the linker will detect object files which have table imports or
definitions, but no table symbols. In that case it will synthesize
symbols for the defined and imported tables.

As a change, relocatable objects are now written with table symbols,
which can cause symbol renumbering in some of the tests. If no object
file requires an indirect function table, none will be written to the
file. Note that for legacy ObjFile inputs, this test is conservative: as
we don't have relocs for each use of the indirecy function table, we
just assume that any incoming indirect function table should be
propagated to the output.

Differential Revision: https://reviews.llvm.org/D91870

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Revert "[WebAssembly] Add support for table linking to wasm-ld"

This reverts commit 38dfce706f796dc109ea495dd69a8cb4c8fa819d.
CI discovered a bug where the table is exported twice: see
D91870

[WebAssembly] Add support for table linking to wasm-ld

This patch adds support to wasm-ld for linking multiple table references
together, in a manner similar to wasm globals. The indirect function
t

[WebAssembly] Add support for table linking to wasm-ld

This patch adds support to wasm-ld for linking multiple table references
together, in a manner similar to wasm globals. The indirect function
table is synthesized as needed.

To manage the transitional period in which the compiler doesn't yet
produce TABLE_NUMBER relocations and doesn't residualize table symbols,
the linker will detect object files which have table imports or
definitions, but no table symbols. In that case it will synthesize
symbols for the defined and imported tables.

As a change, relocatable objects are now written with table symbols,
which can cause symbol renumbering in some of the tests. If no object
file requires an indirect function table, none will be written to the
file. Note that for legacy ObjFile inputs, this test is conservative: as
we don't have relocs for each use of the indirecy function table, we
just assume that any incoming indirect function table should be
propagated to the output.

Differential Revision: https://reviews.llvm.org/D91870

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[lld][WebAssembly] Add support for handling table symbols

This commit adds table symbol support in a partial way, while still
including some special cases for the __indirect_function_table symbol.
N

[lld][WebAssembly] Add support for handling table symbols

This commit adds table symbol support in a partial way, while still
including some special cases for the __indirect_function_table symbol.
No change in tests.

Differential Revision: https://reviews.llvm.org/D94075

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[lld][WebAssembly] Split __wasm_apply_relocs function in two

We have two types of relocations that we apply on startup:
1. Relocations that apply to wasm globals
2. Relocations that apply to wasm me

[lld][WebAssembly] Split __wasm_apply_relocs function in two

We have two types of relocations that we apply on startup:
1. Relocations that apply to wasm globals
2. Relocations that apply to wasm memory

The first set of relocations use only the `__memory_base` import to
update a set of internal globals. Because wasm globals are thread local
these need to run on each thread. Memory relocations, like static
constructors, must only be run once.

To ensure global relocations run on all threads and because the only
depend on the immutable `__memory_base` import we can run them during
the WebAssembly start functions, instead of waiting until the
post-instantiation __wasm_call_ctors.

Differential Revision: https://reviews.llvm.org/D93066

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[lld][WebAssembly] Delay creation of internal __wasm_memory_init function

This also allows for its creation to be conditional so it is completely
elided when not needed.

Differential Revision: http

[lld][WebAssembly] Delay creation of internal __wasm_memory_init function

This also allows for its creation to be conditional so it is completely
elided when not needed.

Differential Revision: https://reviews.llvm.org/D93035

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[lld] Delete unused declarations

Notes:

* runMSVCLinker: remnant of r338615
* wasm markSymbol: remnant of r374275
* wasm addDataAddressGlobal: accidentally added by r372779
* MachO Writer::createSy

[lld] Delete unused declarations

Notes:

* runMSVCLinker: remnant of r338615
* wasm markSymbol: remnant of r374275
* wasm addDataAddressGlobal: accidentally added by r372779
* MachO Writer::createSymtabContents: accidentally added by D76839

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[lld][WebAssembly] Fix malformed output with -pie + --shared-memory

The conditional guarding createInitMemoryFunction was incorrect and
didn't match that guarding the creation of the associated symb

[lld][WebAssembly] Fix malformed output with -pie + --shared-memory

The conditional guarding createInitMemoryFunction was incorrect and
didn't match that guarding the creation of the associated symbol.

Rather that reproduce the same conditions in multiple places we can
simply use the presence of the associated symbol.

Also, add an assertion that would have caught this bug.

Also, add a new test for this flag combination.

This is part of an ongoing effort to enable dynamic linking with
threads in emscripten.

See https://github.com/emscripten-core/emscripten/issues/3494

Differential Revision: https://reviews.llvm.org/D92520

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[lld][WebAssembly] Ensure stub symbols always get address 0

Without this extra flag we can't distingish between stub functions and
functions that happen to have address 0 (relative to __table_base).

[lld][WebAssembly] Ensure stub symbols always get address 0

Without this extra flag we can't distingish between stub functions and
functions that happen to have address 0 (relative to __table_base).

Adding this flag bit the base symbol class actually avoids growing the
SymbolUnion struct which would not be true if we added it to the
FunctionSymbol subclass (due to bitbacking).

The previous approach of setting it's table index to zero worked for
normal static relocations but not for `-fPIC` code.

See https://github.com/emscripten-core/emscripten/issues/12819

Differential Revision: https://reviews.llvm.org/D92038

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[WebAssembly] GC constructor functions in otherwise unused archive objects

This allows `__wasilibc_populate_libpreopen` to be GC'd in more cases
where it isn't needed, including when linked from Rus

[WebAssembly] GC constructor functions in otherwise unused archive objects

This allows `__wasilibc_populate_libpreopen` to be GC'd in more cases
where it isn't needed, including when linked from Rust's libstd.

Differential Revision: https://reviews.llvm.org/D85062

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[WebAssembly] New-style command support

This adds support for new-style command support. In this mode, all exports
are considered command entrypoints, and the linker inserts calls to
`__wasm_call_ct

[WebAssembly] New-style command support

This adds support for new-style command support. In this mode, all exports
are considered command entrypoints, and the linker inserts calls to
`__wasm_call_ctors` and `__wasm_call_dtors` for all such entrypoints.

This enables support for:

- Command entrypoints taking arguments other than strings and return values
other than `int`.
- Multicall executables without requiring on the use of string-based
command-line arguments.

This new behavior is disabled when the input has an explicit call to
`__wasm_call_ctors`, indicating code not expecting new-style command
support.

This change does mean that wasm-ld no longer supports DCE-ing the
`__wasm_call_ctors` function when there are no calls to it. If there are no
calls to it, and there are ctors present, we assume it's wasm-ld's job to
insert the calls. This seems ok though, because if there are ctors present,
the program is expecting them to be called. This change affects the
init-fini-gc.ll test.

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[WebAssembly] 64-bit (function) pointer fixes.

Accounting for the fact that Wasm function indices are 32-bit, but in wasm64 we want uniform 64-bit pointers.
Includes reloc types for 64-bit table ind

[WebAssembly] 64-bit (function) pointer fixes.

Accounting for the fact that Wasm function indices are 32-bit, but in wasm64 we want uniform 64-bit pointers.
Includes reloc types for 64-bit table indices.

Differential Revision: https://reviews.llvm.org/D83729

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[lld][WebAssembly] Refactor markLive.cpp. NFC

This pattern matches the ELF implementation add if also useful as
part of a planned change where running `mark` more than once is needed.

Differential

[lld][WebAssembly] Refactor markLive.cpp. NFC

This pattern matches the ELF implementation add if also useful as
part of a planned change where running `mark` more than once is needed.

Differential Revision: https://reviews.llvm.org/D68749

llvm-svn: 374275

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[WebAssembly] Initialize memory in start function

Summary:
- `__wasm_init_memory` is now the WebAssembly start function instead
of being called from `__wasm_call_ctors` or called directly by the

[WebAssembly] Initialize memory in start function

Summary:
- `__wasm_init_memory` is now the WebAssembly start function instead
of being called from `__wasm_call_ctors` or called directly by the
runtime.
- Adds a new synthetic data symbol `__wasm_init_memory_flag` that is
atomically incremented from zero to one by the thread responsible
for initializing memory.
- All threads now unconditionally perform data.drop on all passive
segments.
- Removes --passive-segments and --active-segments flags and controls
segment type based on --shared-memory instead. The deleted flags
were only present to ameliorate the upgrade path in Emscripten.

Reviewers: sbc100, aheejin

Subscribers: dschuff, jgravelle-google, sunfish, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65783

llvm-svn: 370965

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[WebAssembly] Implement NO_STRIP

This patch implements support for the NO_STRIP flag, which will allow
__attribute__((used)) to be implemented.

This accompanies https://reviews.llvm.org/D62542, whi

[WebAssembly] Implement NO_STRIP

This patch implements support for the NO_STRIP flag, which will allow
__attribute__((used)) to be implemented.

This accompanies https://reviews.llvm.org/D62542, which moves to setting the
NO_STRIP flag, and will continue to set EXPORTED for Emscripten targets for
compatibility.

Differential Revision: https://reviews.llvm.org/D66968

llvm-svn: 370416

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[WebAssembly] Rename variale references in comments after VariableName -> variableName change

llvm-svn: 366192

[Coding style change][lld] Rename variables for non-ELF ports

This patch does the same thing as r365595 to other subdirectories,
which completes the naming style change for the entire lld directory.

[Coding style change][lld] Rename variables for non-ELF ports

This patch does the same thing as r365595 to other subdirectories,
which completes the naming style change for the entire lld directory.

With this, the naming style conversion is complete for lld.

Differential Revision: https://reviews.llvm.org/D64473

llvm-svn: 365730

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[WebAssembly] Add option to emit passive segments

Summary:
Adds `--passive-segments` and `--active-segments` flags to control
what kind of segments are emitted. For now the default is always
to emit

[WebAssembly] Add option to emit passive segments

Summary:
Adds `--passive-segments` and `--active-segments` flags to control
what kind of segments are emitted. For now the default is always
to emit active segments so this is not a breaking change, but in
the future the default will be changed to passive segments when
shared memory is requested and active segments otherwise. When
passive segments are emitted, corresponding memory.init and
data.drop instructions are emitted in a `__wasm_init_memory`
function that is automatically called at the beginning of
`__wasm_call_ctors`.

Reviewers: sbc100, aheejin, dschuff

Subscribers: azakai, dschuff, jgravelle-google, sunfish, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59343

llvm-svn: 365088

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[WebAssembly] Fix for discarded init functions

When a function is excluded via comdat we shouldn't add it to the
final list of init functions.

Differential Revision: https://reviews.llvm.org/D62983

[WebAssembly] Fix for discarded init functions

When a function is excluded via comdat we shouldn't add it to the
final list of init functions.

Differential Revision: https://reviews.llvm.org/D62983

llvm-svn: 362769

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[WebAssembly] Apply data relocations at runtime in shared objects

See: https://github.com/WebAssembly/tool-conventions/blob/master/DynamicLinking.md

Data section relocations in wasm shared librarie

[WebAssembly] Apply data relocations at runtime in shared objects

See: https://github.com/WebAssembly/tool-conventions/blob/master/DynamicLinking.md

Data section relocations in wasm shared libraries are applied by the
library itself at static constructor time. This change adds a new
synthetic function that applies relocations to relevant memory locations
on startup.

Differential Revision: https://reviews.llvm.org/D59278

llvm-svn: 357715

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