[lld] Use value_or instead of getValueOr (NFC)

[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] 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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[MC][WebAssembly] Fix crash when relocation addend underlows U32

For the object file writer we need to allow the underflow (ar write
zero), but for the final linker output we should probably generat

[MC][WebAssembly] Fix crash when relocation addend underlows U32

For the object file writer we need to allow the underflow (ar write
zero), but for the final linker output we should probably generate an
error (I've left that as a TODO for now).

Fixes: https://github.com/llvm/llvm-project/issues/54012

Differential Revision: https://reviews.llvm.org/D120522

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fix comment typos to cycle bots

[WebAssembly] Support R_WASM_MEMORY_ADDR_TLS_SLEB64 for wasm64

Also fixed TLS tests swapping addr & value in store op
Differential Revision: https://reviews.llvm.org/D106096

[WebAssembly] Fixed LLD generation of 64-bit __wasm_apply_data_relocs

Differential Revision: https://reviews.llvm.org/D105863

[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] Fix crash calling weakly undefined function in PIC code

Differential Revision: https://reviews.llvm.org/D104495

[WebAssembly] Fix PIC/GOT codegen for wasm64

__table_base is know 64-bit, since in LLVM it represents a function pointer offset
__table_base32 is a copy in wasm32 for use in elem init expr, since no

[WebAssembly] Fix PIC/GOT codegen for wasm64

__table_base is know 64-bit, since in LLVM it represents a function pointer offset
__table_base32 is a copy in wasm32 for use in elem init expr, since no truncation may be used there.
New reloc R_WASM_TABLE_INDEX_REL_SLEB64 added

Differential Revision: https://reviews.llvm.org/D101784

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[lld][WebAssembly] Enable string tail merging in debug sections

This is a followup to https://reviews.llvm.org/D97657 which
applied string tail merging to data segments.

Fixes: https://bugs.llvm.or

[lld][WebAssembly] Enable string tail merging in debug sections

This is a followup to https://reviews.llvm.org/D97657 which
applied string tail merging to data segments.

Fixes: https://bugs.llvm.org/show_bug.cgi?id=48828

Differential Revision: https://reviews.llvm.org/D102436

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[lld][WebAssembly] Refactor input chunk class hierarchy. NFC

The main motivation for this refactor is to remove the subclass
relationship between the InputSegment and MergeInputSegment and
Syntentic

[lld][WebAssembly] Refactor input chunk class hierarchy. NFC

The main motivation for this refactor is to remove the subclass
relationship between the InputSegment and MergeInputSegment and
SyntenticMergedInputSegment so that we can use the merging classes for
debug sections which are not data segments.

In the process of refactoring I also remove all the virtual functions
from the class hierarchy and try to reuse techniques used in the ELF
linker (see `lld/ELF/InputSections.h`).

Differential Revision: https://reviews.llvm.org/D102546

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[lld][WebAssembly] Remove relocation target verification

We have this extra step in wasm-ld that doesn't exist in other lld
backend which verifies the existing contents of the relocation targets.
Th

[lld][WebAssembly] Remove relocation target verification

We have this extra step in wasm-ld that doesn't exist in other lld
backend which verifies the existing contents of the relocation targets.
This was originally intended as an extra form of double checking and an
aid to compiler developers. However it has always been somewhat
controversial and there have been suggestions in the past the we simply
remove it.

My motivation for removing it now is that its causing me a headache
when trying to fix an issue with negative addends. In the case of
negative addends that final result can be wrapped/negative but this
checking code would require significant modification to be able to deal
with that case. For example with some test cases I'm looking at I'm
seeing error like this:

```
wasm-ld: warning: /usr/local/google/home/sbc/dev/wasm/llvm-build/tools/lld/test/wasm/Output/merge-string.s.tmp.o:(.rodata_relocs): unexpected existing value for R_WASM_MEMORY_ADDR_I32: existing=FFFFFFFA expected=FFFFFFFFFFFFFFFA
```

Rather than try to refactor `calcExpectedValue` to somehow return two
different types of results (32 and 64-bit) depending on the relocation
type, I think we can just remove this code.

Differential Revision: https://reviews.llvm.org/D102265

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Reland: "[lld][WebAssembly] Initial support merging string data"

This change was originally landed in: 5000a1b4b9edeb9e994f2a5b36da8d48599bea49
It was reverted in: 061e071d8c9b98526f35cad55a918a4f16

Reland: "[lld][WebAssembly] Initial support merging string data"

This change was originally landed in: 5000a1b4b9edeb9e994f2a5b36da8d48599bea49
It was reverted in: 061e071d8c9b98526f35cad55a918a4f1615afd4

This change adds support for a new WASM_SEG_FLAG_STRINGS flag in
the object format which works in a similar fashion to SHF_STRINGS
in the ELF world.

Unlike the ELF linker this support is currently limited:
- No support for SHF_MERGE (non-string merging)
- Always do full tail merging ("lo" can be merged with "hello")
- Only support single byte strings (p2align 0)

Like the ELF linker merging is only performed at `-O1` and above.

This fixes part of https://bugs.llvm.org/show_bug.cgi?id=48828,
although crucially it doesn't not currently support debug sections
because they are not represented by data segments (they are custom
sections)

Differential Revision: https://reviews.llvm.org/D97657

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Revert "[lld][WebAssembly] Initial support merging string data"

This reverts commit 5000a1b4b9edeb9e994f2a5b36da8d48599bea49.
Breaks tests, see https://reviews.llvm.org/D97657#2749151

Easily repros

Revert "[lld][WebAssembly] Initial support merging string data"

This reverts commit 5000a1b4b9edeb9e994f2a5b36da8d48599bea49.
Breaks tests, see https://reviews.llvm.org/D97657#2749151

Easily repros locally with `ninja check-llvm-mc-webassembly`.

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[lld][WebAssembly] Initial support merging string data

This change adds support for a new WASM_SEG_FLAG_STRINGS flag in
the object format which works in a similar fashion to SHF_STRINGS
in the ELF w

[lld][WebAssembly] Initial support merging string data

This change adds support for a new WASM_SEG_FLAG_STRINGS flag in
the object format which works in a similar fashion to SHF_STRINGS
in the ELF world.

Unlike the ELF linker this support is currently limited:
- No support for SHF_MERGE (non-string merging)
- Always do full tail merging ("lo" can be merged with "hello")
- Only support single byte strings (p2align 0)

Like the ELF linker merging is only performed at `-O1` and above.

This fixes part of https://bugs.llvm.org/show_bug.cgi?id=48828,
although crucially it doesn't not currently support debug sections
because they are not represented by data segments (they are custom
sections)

Differential Revision: https://reviews.llvm.org/D97657

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[WebAssembly] Add new relocation for location relative data

This `R_WASM_MEMORY_ADDR_SELFREL_I32` relocation represents an offset
between its relocating address and the symbol address. It's very sim

[WebAssembly] Add new relocation for location relative data

This `R_WASM_MEMORY_ADDR_SELFREL_I32` relocation represents an offset
between its relocating address and the symbol address. It's very similar
to `R_X86_64_PC32` but restricted to be used for only data segments.

```
S + A - P
```

A: Represents the addend used to compute the value of the relocatable
field.
P: Represents the place of the storage unit being relocated.
S: Represents the value of the symbol whose index resides in the
relocation entry.

Proposal: https://github.com/WebAssembly/tool-conventions/issues/162

Differential Revision: https://reviews.llvm.org/D96659

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[lld][WebAssembly] Rename methods/members to match ELF backend. NFC.

Specifically:

- InputChunk::outputOffset -> outSecOffset
- Symbol::get/setVirtualAddress -> get/setVA
- add InputChunk::getOffse

[lld][WebAssembly] Rename methods/members to match ELF backend. NFC.

Specifically:

- InputChunk::outputOffset -> outSecOffset
- Symbol::get/setVirtualAddress -> get/setVA
- add InputChunk::getOffset helper that takes an offset

These are mostly in preparation for adding support for
SHF_MERGE/SHF_STRINGS but its also good to align with ELF where
possible.

Differential Revision: https://reviews.llvm.org/D97595

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[lld][WebAssembly] Delay the merging of data section when dynamic linking

With dynamic linking we have the current limitation that there can be
only a single active data segment (since we use __memo

[lld][WebAssembly] Delay the merging of data section when dynamic linking

With dynamic linking we have the current limitation that there can be
only a single active data segment (since we use __memory_base as the
load address and we can't do arithmetic in constant expresions).

This change delays the merging of active segments until a little later
in the linking process which means that the grouping of data by section,
and the magic __start/__end symbols work as expected under dynamic
linking.

Differential Revision: https://reviews.llvm.org/D96453

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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] Use -1 as tombstone value for discarded code ranges

Under existing behavior discarded functions are relocated to have the start pc
0. This causes problems when debugging as they typically over

[lld] Use -1 as tombstone value for discarded code ranges

Under existing behavior discarded functions are relocated to have the start pc
0. This causes problems when debugging as they typically overlap the first
function and lldb symbol resolution frequently chooses a discarded function
instead of the correct one. Using the value -1 or -2 (depending on which DWARF
section we are writing) is sufficient to prevent lldb from resolving to these
symbols.

Reviewed By: MaskRay, yurydelendik, sbc100

Differential Revision: https://reviews.llvm.org/D91803

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[WebAssembly] Added R_WASM_FUNCTION_OFFSET_I64 for use with DWARF DW_AT_low_pc

Needed for wasm64, see discussion in https://reviews.llvm.org/D91203

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

[WebAssembly] Added R_WASM_FUNCTION_OFFSET_I64 for use with DWARF DW_AT_low_pc

Needed for wasm64, see discussion in https://reviews.llvm.org/D91203

Differential Revision: https://reviews.llvm.org/D91395

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[WebAssembly] Add new relocation type for TLS data symbols

These relocations represent offsets from the __tls_base symbol.

Previously we were just using normal MEMORY_ADDR relocations and relying
o

[WebAssembly] Add new relocation type for TLS data symbols

These relocations represent offsets from the __tls_base symbol.

Previously we were just using normal MEMORY_ADDR relocations and relying
on the linker to select a segment-offset rather and absolute value in
Symbol::getVirtualAddress(). Using an explicit relocation type allows
allow us to clearly distinguish absolute from relative relocations based
on the relocation information alone.

One place this is useful is being able to reject absolute relocation in
the PIC case, but still accept TLS relocations.

Differential Revision: https://reviews.llvm.org/D91276

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[lld][WebAssembly] Give better warnings on bad relocation sites

Differential Revision: https://reviews.llvm.org/D90443

[WebAssembly] Improved LLD error messages in case of mixed wasm32/wasm64 object files

Differential Revision: https://reviews.llvm.org/D90428