[wasm-ld] Define a `__heap_end` symbol marking the end of allocated memory.

Define a `__heap_end` symbol that marks the end of the memory region
that starts at `__heap_base`. This will allow malloc

[wasm-ld] Define a `__heap_end` symbol marking the end of allocated memory.

Define a `__heap_end` symbol that marks the end of the memory region
that starts at `__heap_base`. This will allow malloc implementations to
know how much memory they can use at `__heap_base` even if someone has
done a `memory.grow` before they can initialize their state.

Differential Revision: https://reviews.llvm.org/D136110

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Use value instead of getValue (NFC)

Use has_value instead of hasValue (NFC)

[lld][WebAssembly] Don't apply data relocations at static constructor time

Instead, export `__wasm_apply_data_relocs` and `__wasm_call_ctors`
separately.

This is required since user code in a share

[lld][WebAssembly] Don't apply data relocations at static constructor time

Instead, export `__wasm_apply_data_relocs` and `__wasm_call_ctors`
separately.

This is required since user code in a shared library (such as static
constructors) should not be run until relocations have been applied to
all loaded libraries.

See: https://github.com/emscripten-core/emscripten/issues/17295

Differential Revision: https://reviews.llvm.org/D128515

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

This reverts commit aa8feeefd3ac6c78ee8f67bf033976fc7d68bc6d.

Don't use Optional::hasValue (NFC)

Don't use Optional::hasValue (NFC)

Don't use Optional::hasValue (NFC)

fix comment typos to cycle bots

[lld] Use value_or instead of getValueOr (NFC)

[lld][WebAssembly] Revert moving of data relocations to start function

Back in https://reviews.llvm.org/D117412 we moved the application of
data reloctions to the wasm start function.

However, beca

[lld][WebAssembly] Revert moving of data relocations to start function

Back in https://reviews.llvm.org/D117412 we moved the application of
data reloctions to the wasm start function.

However, because the dynamic linker doesn't know the final addresses
at module instantiation time, this proved to be too early and the
relocations could be applied with the wrong values.

Fixes: https://github.com/emscripten-core/emscripten/issues/17150

Differential Revision: https://reviews.llvm.org/D127333

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[lld][WebAssembly] Remove unnecessary accessor methods. NFC

This is less code, and matches more closely the ELF linker.

Differential Revision: https://reviews.llvm.org/D126979

[lld][WebAssembly] Avoid importing/exporting hidden symbols in shared libraries

We have some special handling for weakly defined symbols where we both
import and export them, but this is not needed

[lld][WebAssembly] Avoid importing/exporting hidden symbols in shared libraries

We have some special handling for weakly defined symbols where we both
import and export them, but this is not needed for hidden symbols which
should never be imported or exported.

See https://github.com/emscripten-core/emscripten/pull/16972

This should also help with:
https://github.com/emscripten-core/emscripten/issues/15487

Differential Revision: https://reviews.llvm.org/D126491

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[lld][WebAssembly] Allow use of statically allocated TLS region.

It turns out we were already allocating static address space for TLS
data along with the non-TLS static data, but this space was goin

[lld][WebAssembly] Allow use of statically allocated TLS region.

It turns out we were already allocating static address space for TLS
data along with the non-TLS static data, but this space was going
unused/ignored.

With this change, we include the TLS segment in `__wasm_init_memory`
(which does the work of loading the passive segments into memory when a
module is first loaded). We also set the `__tls_base` global to point
to the start of this segment.

This means that the runtime can use this static copy of the TLS data for
the first/primary thread if it chooses, rather than doing a runtime
allocation prior to calling `__wasm_init_tls`.

Practically speaking, this will allow emscripten to avoid dynamic
allocation of TLS region on the main thread.

Differential Revision: https://reviews.llvm.org/D126107

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[lld][WebAssembly] Fix crash accessing non-live __tls_base symbol

In programs that don't otherwise depend on `__tls_base` it won't
be marked as live. However this symbol is used internally in
a cou

[lld][WebAssembly] Fix crash accessing non-live __tls_base symbol

In programs that don't otherwise depend on `__tls_base` it won't
be marked as live. However this symbol is used internally in
a couple of places do we need to mark it as live explictily in
those places.

Fixes: #54386

Differential Revision: https://reviews.llvm.org/D121931

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[lld][WebAssembly] Take advantage of extended const expressions when available

In particular we use these in two places:

1. When building PIC code we no longer need to combine output segments
in

[lld][WebAssembly] Take advantage of extended const expressions when available

In particular we use these in two places:

1. When building PIC code we no longer need to combine output segments
into a single segment that can be initialized at `__memory_base`.
Instead each segment can encode its offset from `__memory_base` in
its initializer. e.g.

```
(i32.add (global.get __memory_base) (i32.const offset)
```

2. When building PIC code we no longer need to relocation internalized
global addresses. We can just initialize them with their correct
offsets.

Differential Revision: https://reviews.llvm.org/D121420

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[lld][WebAssembly] Add --unresolved-symbols=import-dynamic

This is a new mode for handling unresolved symbols that allows all
symbols to be imported in the same that they would be in the case of
`-f

[lld][WebAssembly] Add --unresolved-symbols=import-dynamic

This is a new mode for handling unresolved symbols that allows all
symbols to be imported in the same that they would be in the case of
`-fpie` or `-shared`, but generting an otherwise fixed/non-relocatable
binary.

Code linked in this way should still be compiled with `-fPIC` so that
data symbols can be resolved via imports.

This essentially allows the building of static binaries that have
dynamic imports. See:
https://github.com/emscripten-core/emscripten/issues/12682

As with other uses of the experimental dynamic linking ABI, this
behaviour will produce a warning unless run with `--experimental-pic`.

Differential Revision: https://reviews.llvm.org/D91577

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[lld][WebAssembly] Apply global relocs before data relocs

Since the code for apply data relocations can sometimes use
the values stored in he globals, they need to be relocated
before the data reloc

[lld][WebAssembly] Apply global relocs before data relocs

Since the code for apply data relocations can sometimes use
the values stored in he globals, they need to be relocated
before the data relocations can be run.

Fixes: https://github.com/emscripten-core/emscripten/issues/13398

Differential Revision: https://reviews.llvm.org/D119666

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Re-land [LLD] Remove global state in lldCommon

Move all variables at file-scope or function-static-scope into a hosting structure (lld::CommonLinkerContext) that lives at lldMain()-scope. Drivers wi

Re-land [LLD] Remove global state in lldCommon

Move all variables at file-scope or function-static-scope into a hosting structure (lld::CommonLinkerContext) that lives at lldMain()-scope. Drivers will inherit from this structure and add their own global state, in the same way as for the existing COFFLinkerContext.

See discussion in https://lists.llvm.org/pipermail/llvm-dev/2021-June/151184.html

The previous land f860fe362282ed69b9d4503a20e5d20b9a041189 caused issues in https://lab.llvm.org/buildbot/#/builders/123/builds/8383, fixed by 22ee510dac9440a74b2e5b3fe3ff13ccdbf55af3.

Differential Revision: https://reviews.llvm.org/D108850

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[lld][WebAssembly] Perform data relocations during start function

We already perform memory initialization and apply global relocations
during start. It makes sense to performs data relocations too

[lld][WebAssembly] Perform data relocations during start function

We already perform memory initialization and apply global relocations
during start. It makes sense to performs data relocations too. I think
the reason we were not doing this already is solely historical.

Differential Revision: https://reviews.llvm.org/D117412

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Revert [LLD] Remove global state in lldCommon

It seems to be causing issues on https://lab.llvm.org/buildbot/#/builders/123/builds/8383

[LLD] Remove global state in lldCommon

Move all variables at file-scope or function-static-scope into a hosting structure (lld::CommonLinkerContext) that lives at lldMain()-scope. Drivers will inher

[LLD] Remove global state in lldCommon

Move all variables at file-scope or function-static-scope into a hosting structure (lld::CommonLinkerContext) that lives at lldMain()-scope. Drivers will inherit from this structure and add their own global state, in the same way as for the existing COFFLinkerContext.

See discussion in https://lists.llvm.org/pipermail/llvm-dev/2021-June/151184.html

Differential Revision: https://reviews.llvm.org/D108850

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[wasm] Use nullptr instead of NULL (NFC)

Identified with modernize-use-nullptr.

[lld][WebAssembly] Generate TLS relocation code also when linking statically

Previously relocations were only generated for PIC output, but
relocations for TLS GOT entries are always needed when sha

[lld][WebAssembly] Generate TLS relocation code also when linking statically

Previously relocations were only generated for PIC output, but
relocations for TLS GOT entries are always needed when shared
memory is enabled, not just in PIC mode.

This means that the `__wasm_apply_global_tls_relocs` is now
generated even for statically linked (non-PIC) output. Without
this the globals that hold the addresses of TLS symbols are
not set correctly.

Differential Revision: https://reviews.llvm.org/D112833

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[lld][WebAssembly] Initialize bss segments using memory.fill

Previously we were relying on the dynamic loader to take care of this
but it simple and correct for us to do it here instead.

Now we ini

[lld][WebAssembly] Initialize bss segments using memory.fill

Previously we were relying on the dynamic loader to take care of this
but it simple and correct for us to do it here instead.

Now we initialize bss segments as part of `__wasm_init_memory` at the
same time we initialize passive segments.

In addition we extent the us of `__wasm_init_memory` outside of shared
memory situations. Specifically it is now used to initialize bss
segments when the memory is imported.

Differential Revision: https://reviews.llvm.org/D112667

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