Commit Graph

633 Commits

Author SHA1 Message Date
Sam Clegg 758633f922 [lld][WebAssembly] Add new `--import-undefined` option
This change revisits https://reviews.llvm.org/D79248 which originally
added support for the --unresolved-symbols flag.

At the time I thought it would make sense to add a third option to this
flag called `import-functions` but it turns out (as was suspects by on
the reviewers IIRC) that this option can be authoganal.

Instead I've added a new option called `--import-undefined` that only
operates on symbols that can be imported (for example, function symbols
can always be imported as opposed to data symbols we can only be
imported when compiling with PIC).

This option gives us the full expresivitiy that emscripten needs to be
able allow reporting of undefined data symbols as well as the option to
disable that.

This change does remove the `--unresolved-symbols=import-functions`
option, which is been in the codebase now for about a year but I would
be extremely surprised if anyone was using it.

Differential Revision: https://reviews.llvm.org/D103290
2021-06-17 11:44:21 -07:00
Sam Clegg c1a59fa550 [lld][WebAssemlby] Fix for string merging of -dwarf-5 sections
We were mistakenly treating `.debug_str_offsets` as a string mergable
section when it is not (it contains integers not strings).  This is an
indication that we really should find a way to store flags for custom
sections.

Fixes: https://bugs.llvm.org/show_bug.cgi?id=48828
Fixes: https://bugs.chromium.org/p/chromium/issues/detail?id=1172217

Differential Revision: https://reviews.llvm.org/D103486
2021-06-01 14:33:56 -07:00
Sam Clegg 8544b40b6e [lld][WebAssembly] Fix for PIC output + TLS + non-shared-memory
Prior to this change build with `-shared/-pie` and using TLS (but
without -shared-memory) would hit this assert:

  "Currenly only a single data segment is supported in PIC mode"

This is because we were not including TLS data when merging data
segments.  However, when we build without shared-memory (i.e.  without
threads) we effectively lower away TLS into a normal active data
segment.. so we were ending up with two active data segments: the merged
data, and the lowered TLS data.

To fix this problem we can instead avoid combining data segments at
all when running in shared memory mode (because in this case all
segment initialization is passive).  And then in non-shared memory
mode we know that TLS has been lowered and therefore we can can
and should combine all segments.

So with this new behavior we have two different modes:

1. With shared memory / mutli-threaded: Never combine data segments
   since it is not necessary.  (All data segments as passive already).

2. Wihout shared memory / single-threaded: Combine *all* data segments
   since we treat TLS as normal data.  (We end up with a single
   active data segment).

Differential Revision: https://reviews.llvm.org/D102937
2021-05-21 15:16:47 -07:00
Wouter van Oortmerssen 3a293cbf13 [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
2021-05-20 09:59:31 -07:00
Sam Clegg 356b85edd7 [lld][WebAssembly] Fix for string tail merging and -r/--relocatable
Ensure that both SyntheticMergedChunk and all MergeInfoChunks that it
comprises are assigned the correct output section.  Without this we
would crash when outputting relocations in --relocatable mode.

Fixes: https://github.com/emscripten-core/emscripten/issues/14220

Differential Revision: https://reviews.llvm.org/D102806
2021-05-19 15:25:58 -07:00
Sam Clegg 45b7cf9955 [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
2021-05-18 12:25:39 -07:00
Sam Clegg 5a9b25e15b [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
2021-05-17 21:01:17 -07:00
Sam Clegg 119f61af3a [lld][WebAssembly] Remove unused method declaration. NFC
This method was removed in https://reviews.llvm.org/D102265
but the declaration was missed.
2021-05-14 15:54:33 -07:00
Sam Clegg 3041b16f73 [WebAssembly] Add TLS data segment flag: WASM_SEG_FLAG_TLS
Previously the linker was relying solely on the name of the segment
to imply TLS.

Differential Revision: https://reviews.llvm.org/D102202
2021-05-12 13:31:02 -07:00
Sam Clegg 19cedd3cd3 [lld][WebAssembly] Fix for string merging + negative addends
Don't include the relocation addend when calculating the
virtual address of a symbol.  Instead just pass the symbol's
offset and add the addend afterwards.

Without this fix we hit the `offset is outside the section`
error in MergeInputSegment::getSegmentPiece.

This fixes a real world error we were are seeing in emscripten.

Differential Revision: https://reviews.llvm.org/D102271
2021-05-11 17:47:57 -07:00
Sam Clegg b49a798e71 [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
2021-05-11 12:05:14 -07:00
Sam Clegg 3b8d2be527 Reland: "[lld][WebAssembly] Initial support merging string data"
This change was originally landed in: 5000a1b4b9
It was reverted in: 061e071d8c

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
2021-05-10 16:03:38 -07:00
Nico Weber 061e071d8c Revert "[lld][WebAssembly] Initial support merging string data"
This reverts commit 5000a1b4b9.
Breaks tests, see https://reviews.llvm.org/D97657#2749151

Easily repros locally with `ninja check-llvm-mc-webassembly`.
2021-05-10 18:28:28 -04:00
Sam Clegg 5000a1b4b9 [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
2021-05-10 13:15:12 -07:00
Sam Clegg bda8b84884 [lld][WebAssembly] Disallow exporting of TLS symbols
Cross module TLS is currently not supported by our ABI.  This
change makes explicitly exporting a TLS symbol into an error
and prevents implicit exporting (via --export-all).

See https://github.com/emscripten-core/emscripten/issues/14120

Differential Revision: https://reviews.llvm.org/D102044
2021-05-10 09:58:44 -07:00
Sam Clegg 808fcddae4 [lld][WebAssembly] Fix crash with `-pie` without `--allow-undefined`
`shouldImport` was not returning true in PIC mode even though out
assumption elsewhere (in Relocations.cpp:scanRelocations) is that we
don't report undefined symbols in PIC mode today.  This was resulting
functions that were undefined and but also not imported which hits an
assert later on that all functions have valid indexes.

Differential Revision: https://reviews.llvm.org/D101716
2021-05-03 18:04:55 -07:00
Sam Clegg 73332d73e1 [lld][WebAssembly] Do not merge comdat data segments
When running in relocatable mode any input data segments that are part
of a comdat group should not be merged with other segments of the same
name.  This is because the final linker needs to keep the separate so
they can be included/excluded individually.

Often this is not a problem since normally only one section with a given
name `foo` ends up in the output object file.  However, the problem
occurs when one input contains `foo` which part of a comdat and another
object contains a local symbol `foo` we were attempting to merge them.

This behaviour matches (I believe) that of the ELF linker.  See
`LinkerScript.cpp:addInputSec`.

Fixes: https://github.com/emscripten-core/emscripten/issues/9726

Differential Revision: https://reviews.llvm.org/D101703
2021-05-03 16:43:29 -07:00
Sam Clegg a6f406480a [lld][WebAssembly] Add `--export-if-defined`
Unlike the existing `--export` option this will not causes errors
or warnings if the specified symbol is not defined.

See: https://github.com/emscripten-core/emscripten/issues/13736

Differential Revision: https://reviews.llvm.org/D99887
2021-04-29 10:58:45 -07:00
Sam Clegg 3e7bc0da57 [lld][WebAssembly] Allow relocations against non-live global symbols
Just like the in case for function and data symbols this is needed to
support relocations in debug info sections which are allowed contains
relocations against non-live symbols.

The motivating use case is an object file that contains debug info that
references `__stack_pointer` (a local symbol) but does not actually
contain any uses of `__stack_pointer`.

Fixes: https://github.com/emscripten-core/emscripten/issues/14025

Differential Revision: https://reviews.llvm.org/D101399
2021-04-28 10:29:41 -07:00
Andy Wingo 9ac5620cb8 [WebAssembly] Rename WasmLimits::Initial to ::Minimum. NFC.
This patch renames the "Initial" member of WasmLimits to the name used
in the spec, "Minimum".

In the core WebAssembly specification, the Limits data type has one
required "min" member and one optional "max" member, indicating the
minimum required size of the corresponding table or memory, and the
maximum size, if any.

Although the WebAssembly spec does instantiate locally-defined tables
and memories with the initial size being equal to the minimum size, it
can't impose such a requirement for imports.  It doesn't make sense to
require an initial size for a memory import, for example.  The compiler
can only sensibly express the minimum and maximum sizes.

See
https://github.com/WebAssembly/js-types/blob/master/proposals/js-types/Overview.md#naming-of-size-limits
for a related discussion that agrees that the right name of "initial" is
"minimum" when querying the type of a table or memory from JavaScript.
(Of course it still makes sense for JS to speak in terms of an initial
size when it explicitly instantiates memories and tables.)

Differential Revision: https://reviews.llvm.org/D99186
2021-03-24 09:10:11 +01:00
Yuta Saito aa0c571a5f [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
2021-03-08 11:34:10 -08:00
Andy Wingo 51f1ddf8cb [lld][WebAssembly] Allow element sections for nonzero table numbers
This patch fixes LLD to allow element sections for tables whose number
is nonzero.  We also add a test for linking multiple tables, showing
that nonzero table numbers for the indirect function table,
user-declared imported tables, and local user table definitions work.

Differential Revision: https://reviews.llvm.org/D92321
2021-03-05 11:52:28 +01:00
Andy Wingo e638d8b2bc [lld][WebAssembly] -Bsymbolic creates indirect function table if needed
It can be that while processing relocations, we realize that in the end
we need an indirect function table.  Ensure that one is present, in that
case, to avoid writing invalid object files.

Fixes https://bugs.llvm.org/show_bug.cgi?id=49397.

Differential Revision: https://reviews.llvm.org/D97843
2021-03-04 09:28:21 +01:00
Sam Clegg 7d09e1d7cf [lld][WebAssembly] Minor refactor in preparation for SHF_STRINGS supports. NFC.
A couple of small changes to match the ELF linker in preparation
for adding support string mergings.

Differential Revision: https://reviews.llvm.org/D97654
2021-03-01 16:15:29 -08:00
Sam Clegg 14ffbb84aa [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
2021-02-26 17:05:59 -08:00
Andy Wingo 48219d06b1 [lld][WebAssembly] Fix resolveIndirectFunctionTable for relocatable output
For relocatable output that needs the indirect function table, identify
the well-known function table.  This allows us to properly fix the
limits on the imported table, and in a followup will allow the element
section to reference the indirect function table even if it's not
assigned to table number 0.  Adapt tests for import reordering.

Differential Revision: https://reviews.llvm.org/D96770
2021-02-18 09:33:54 +01:00
Andy Wingo f48923e884 [WebAssembly][lld] --importTable flag only imports table if needed
Before, --importTable forced the creation of an indirect function table,
whether it was needed or not.  Now it only imports a table if needed.

Differential Revision: https://reviews.llvm.org/D96872
2021-02-18 09:16:29 +01:00
Andy Wingo 4fc2557308 [WebAssembly][lld] Preassign table number 0 to indirect function table for MVP inputs
MVP object files may import at most one table, and if they do, it must
be assigned table number zero in the output, as the references to that
table are not relocatable.  Ensure that this is the case, even if some
inputs define other tables.

Differential Revision: https://reviews.llvm.org/D96001
2021-02-12 20:20:19 +01:00
Sam Clegg e1617d23ff Revert "[lld][WebAssembly] Fix for weak undefined functions in -pie mode"
This reverts commit ac2be2b6a3.

This causes a whole much of emscripten tests to fail due to newly
undefined symbols appearing.  Will investigate and look into re-landing
later.
2021-02-12 09:04:18 -08:00
Sam Clegg ac2be2b6a3 [lld][WebAssembly] Fix for weak undefined functions in -pie mode
This fixes two somewhat related issues.  Firstly we were never
generating imports for weak functions (even with the `import-functions`
policy for undefined symbols).  Adding a direct call to foo in the
`weak-undefined-pic.s` exposed a crash in the linker which this
change fixes.

Secondly we were failing to call `handleWeakUndefines` for the `-pie`
case which is PIC but doesn't set the undefined symbol policy to
`import-functions`.  With this change `-pie` binaries will by default
call `handleWeakUndefines` which generates the undefined stub handlers
for any weakly undefined symbols.

Fixes: https://github.com/emscripten-core/emscripten/issues/13337

Differential Revision: https://reviews.llvm.org/D95914
2021-02-11 17:16:03 -08:00
Sam Clegg 70f3c6e9e6 [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
2021-02-11 10:54:15 -08:00
Andy Wingo a56e57493b [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
2021-02-11 14:54:45 +01:00
Thomas Lively 067f005500 [lld][WebAssembly] Fix segfault in map file support
The code previously assumed that `getChunk` would return a non-null pointer for
every symbol, but in fact it only returns non-null pointers for DefinedFunction
and DefinedData symbols. This patch fixes the segfault by checking whether
`getChunk` returns a null for each symbol and skipping the mapping output for
any symbols for which it does.

Differential Revision: https://reviews.llvm.org/D88369
2021-02-09 14:42:43 -08:00
Sam Clegg 34d033ca12 [lld][WebAssembly] Allow --export of optional start/stop symbols
This moves the error checking until after all optional
symbols (including the section start/end symbols) have
been created.

Differential Revision: https://reviews.llvm.org/D96318
2021-02-09 13:14:52 -08:00
Sam Clegg 88e4056b44 [lld][WebAssembly] Fix typo in function name
addOptionalGlobalSymbols should be addOptionalGlobalSymbol.

Also, remove unnecessary additional argument to make the signature match
the sibling function: addOptionalDataSymbol.

Differential Revision: https://reviews.llvm.org/D96305
2021-02-08 19:41:01 -08:00
Wouter van Oortmerssen 0d9b17d0ef [WebAssembly] fixed wasm64 data segment init exp not 64-bit
As defined in the spec:
https://github.com/WebAssembly/memory64/blob/master/proposals/memory64/Overview.md

Differential Revision: https://reviews.llvm.org/D95651
2021-02-01 11:32:50 -08:00
Sam Clegg 5c0164890c [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
2021-01-28 08:52:14 -08:00
Sam Clegg 299b0e5ee9 [lld] Consistent help text for `--save-temps`
I noticed that this option was not appearing at all in the `--help`
messages for `wasm-ld` or `ld.lld`.

Add help text and make it consistent across all ports.

Differential Revision: https://reviews.llvm.org/D94925
2021-01-25 10:27:18 -08:00
Sam Clegg b99147b4fa [lld][WebAssembly] Don't defined indirect function table in relocatable output
Object files (and the output --relocatable) should never define
__indirect_function_table.  It should always be linker synthesized
with the final output executable.

Differential Revision: https://reviews.llvm.org/D94993
2021-01-19 12:59:20 -08:00
Arthur Eubanks a231786909 [wasm][LLD] Rename --lto-new-pass-manager to --no-lto-legacy-pass-manager
This follows a similar ELF change.

Reviewed By: MaskRay, sbc100

Differential Revision: https://reviews.llvm.org/D93253
2021-01-19 11:22:40 -08:00
Andy Wingo 831a143e50 [WebAssembly] Change prefix on data segment flags to WASM_DATA_SEGMENT
Element sections will also need flags, so we shouldn't squat the
WASM_SEGMENT namespace.

Depends on D90948.

Differential Revision: https://reviews.llvm.org/D92315
2021-01-19 09:40:42 +01:00
Andy Wingo 6339382807 [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
2021-01-18 16:57:18 +01:00
Derek Schuff 187d771d27 Revert "[WebAssembly] Add support for table linking to wasm-ld"
This reverts commit 38dfce706f.
CI discovered a bug where the table is exported twice: see
D91870
2021-01-15 15:50:41 -08:00
Andy Wingo 38dfce706f [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
2021-01-15 09:21:52 +01:00
Andy Wingo 53e3b81faa [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
2021-01-14 11:13:13 +01:00
Sam Clegg 07b6aeb568 [lld][WebAssembly] Fix for TLS + --relocatable
When running in `-r/--relocatable` we output relocations but the
new TLS relocations type was missing from `ObjFile::calcNewAddend`
causing this combination of inputs/flags to crash the linker.

Also avoid creating tls variables in relocatable mode.  These variables
are only needed when linking final executables.

Fixes: https://github.com/emscripten-core/emscripten/issues/12934
Fixes: PR48506

Differential Revision: https://reviews.llvm.org/D93554
2021-01-13 07:49:39 -08:00
Heejin Ahn 52e240a072 [WebAssembly] Remove exnref and br_on_exn
This removes `exnref` type and `br_on_exn` instruction. This is
effectively NFC because most uses of these were already removed in the
previous CLs.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D94041
2021-01-09 02:02:54 -08:00
Reshabh Sharma fdd6ed8e93 [LLD] Rename lld port driver entry function to a consistent name
Libraries linked to the lld elf library exposes a function named main.
When debugging code linked to such libraries and intending to set a
breakpoint at main, the debugger also sets breakpoint at the main
function at lld elf driver. The possible choice was to rename it to
link but that would again clash with lld::*::link. This patch tries
to consistently rename them to linkerMain.

Differential Revision: https://reviews.llvm.org/D91418
2020-12-18 12:18:37 +05:30
Derek Schuff cb77e877f8 [WebAssembly][lld] Don't mark a file live from an undefine symbol
Live symbols should only cause the files in which they are defined
to become live.

For now this is only tested in emscripten: we're continuing
to work on reducing the test case further for an lld-style
unit test.

Differential Revision: https://reviews.llvm.org/D93472
2020-12-17 11:05:36 -08:00
Arthur Eubanks e814013932 [Wasm][LTO][NPM] Use NPM for LTO with ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER
Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D92867
2020-12-14 10:15:13 -08:00
Derek Schuff dd6412c05c [WebAssembly][lld] Exclude COMDAT sections
Allow exclusion/discarding of custom sections with COMDAT groups.
It piggybacks on the existing COMDAT-handling code, but applies to custom sections as well.

Differential Revision: https://reviews.llvm.org/D92950
2020-12-10 17:47:41 -08:00
Sam Clegg e52881a287 [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
2020-12-10 17:07:39 -08:00
Sam Clegg 199497086e [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
2020-12-10 10:47:18 -08:00
Sam Clegg d8ed639a6a [lld][WebAssembly] Don't emit names for data segments that we omit
Followup to https://reviews.llvm.org/D92909

Differential Revision: https://reviews.llvm.org/D92997
2020-12-09 20:59:26 -08:00
Sam Clegg 9a72d3e3e4 [WebAssembly] Add support for named data sections in wasm binaries
Followup to https://reviews.llvm.org/D91769 which added support
for names globals.

Differential Revision: https://reviews.llvm.org/D92909
2020-12-09 12:57:07 -08:00
Fangrui Song 4701cb41ed [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
2020-12-06 15:26:37 -08:00
Sam Clegg ab58e4cb51 [lld][WebAssembly] Add suppport for PIC + passive data initialization
This change improves our support for shared memory to include
PIC executables (and shared libraries).

To handle this case the linker-generated `__wasm_init_memory`
function (that only exists in shared memory builds) must be
capable of loading memory segements at non-const offsets based
on the runtime value of `__memory_base`.

Differential Revision: https://reviews.llvm.org/D92620
2020-12-04 17:28:23 -08:00
Sam Clegg 1bb79875e4 [lld][WebAssembly] Set memory limits correctly for PIC + shared memory
Don't early return from layoutMemory in PIC mode before we have set the
memory limits.

This matters in particular with shared-memory + PIC because shared
memories require maximum size.

Secondly, when we need a maximum, but the user does not supply one,
default to MAX_INT rather than 0 (defaulting to zero is completely
useless and means that building with -shared didn't previously work at
all without --maximum-memory, because zero is never big enough).

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/D92528
2020-12-03 18:14:28 -08:00
Wouter van Oortmerssen fd65e4815c [WebAssembly] Fixed Writer::createInitMemoryFunction to work for wasm64
Differential Revision: https://reviews.llvm.org/D92348
2020-12-03 16:20:55 -08:00
Sam Clegg 701fa0b5ab [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
2020-12-03 11:06:07 -08:00
Eric Leese 8b8088ac6c [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
2020-12-01 17:06:32 -08:00
Fangrui Song 31e03a9bd9 [WebAssembly] Rename --lto-no-new-pass-manager to --no-lto-new-pass-manager
In addition, disallow `-lto-new-pass-manager` (see D79371).

Note: the ELF port has also adopted --no-lto-new-pass-manager

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D92422
2020-12-01 16:52:37 -08:00
Sam Clegg a38ed62ea8 [lld][WebAssembly] Feedback from D92038. NFC
Differential Revision: https://reviews.llvm.org/D92429
2020-12-01 14:53:59 -08:00
Arthur Eubanks 1314a4938f [LTO][wasm][NewPM] Allow using new pass manager for wasm LTO
Reviewed By: sbc100

Differential Revision: https://reviews.llvm.org/D92150
2020-12-01 12:22:40 -08:00
Sam Clegg 48ddf5e182 [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
2020-11-25 18:26:34 -08:00
Andy Wingo 1933c9d41a [WebAssembly] Factor out WasmTableType in binary format
This commit factors out a WasmTableType definition from WasmTable, as is
the case for WasmGlobal and other data types.  Also add support for
extracting the SymbolName for a table from the linking section's symbol
table.

Differential Revision: https://reviews.llvm.org/D91849
2020-11-25 08:00:08 -08:00
Sam Clegg 1827005cfc [WebAssembly] Add support for named globals in the object format.
Differential Revision: https://reviews.llvm.org/D91769
2020-11-19 00:17:22 -08:00
Sam Clegg 206884bf90 [lld][WebAssembly] Implement --unresolved-symbols
This is a more full featured version of ``--allow-undefined``.
The semantics of the different methods are as follows:

report-all:

   Report all unresolved symbols.  This is the default.  Normally the
   linker will generate an error message for each reported unresolved
   symbol but the option ``--warn-unresolved-symbols`` can change this
   to a warning.

ignore-all:

   Resolve all undefined symbols to zero.  For data and function
   addresses this is trivial.  For direct function calls, the linker
   will generate a trapping stub function in place of the undefined
   function.

import-functions:

   Generate WebAssembly imports for any undefined functions.  Undefined
   data symbols are resolved to zero as in `ignore-all`.  This
   corresponds to the legacy ``--allow-undefined`` flag.

The plan is to followup with a new mode called `import-dynamic` which
allows for statically linked binaries to refer to both data and
functions symbols from the embedder.

Differential Revision: https://reviews.llvm.org/D79248
2020-11-17 16:27:06 -08:00
Nico Weber baa2aa28f5 lld: Add --color-diagnostic to MachO port, harmonize others
This adds `--[no-]color-diagnostics[=auto,never,always]` to
the MachO port and harmonizes the flag in the other ports:
- Consistently use MetaVarName
- Consistently document the non-eq version as alias of the eq version
- Use B<> in the ports that have it (no-op, shorter)
- Fix oversight in COFF port that made the --no flag have the wrong
  prefix

Differential Revision: https://reviews.llvm.org/D91640
2020-11-17 12:58:30 -05:00
Wouter van Oortmerssen 16f02431dc [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
2020-11-13 09:32:31 -08:00
Sam Clegg a28a466210 [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
2020-11-13 07:59:29 -08:00
Sam Clegg 29a3056bb5 [lld][WebAssembly] Allow references to __tls_base without shared memory
Previously we limited the use of atomics and TLS to programs
linked with `--shared-memory`.

However, as of https://reviews.llvm.org/D79530 we now allow
programs that use atomic to be linked without `--shared-memory`.
For this to be useful we also want to all TLS usage in such
programs.  In this case, since we know we are single threaded
we simply include the TLS data as a regular active segment
and create an immutable `__tls_base` global that point to the
start of this segment.

Fixes: https://github.com/emscripten-core/emscripten/issues/12489

Differential Revision: https://reviews.llvm.org/D91115
2020-11-10 17:58:06 -08:00
Sam Clegg 9d1409df87 [lld][WebAssembly] Give better warnings on bad relocation sites
Differential Revision: https://reviews.llvm.org/D90443
2020-10-30 10:11:04 -07:00
Wouter van Oortmerssen b8c2d60df5 [WebAssembly] Improved LLD error messages in case of mixed wasm32/wasm64 object files
Differential Revision: https://reviews.llvm.org/D90428
2020-10-29 17:15:59 -07:00
Sam Clegg 84129150ce [lld][WebAssembly] Fix memory size in dylink section for -pie exectuables
This field to represents the amount of static data needed by
an dynamic library or executable it should not include things
like heap or stack areas, which in the case of `-pie` are
not determined until runtime (e.g. __stack_pointer is imported).

Differential Revision: https://reviews.llvm.org/D90261
2020-10-27 16:05:52 -07:00
Paulo Matos 388fb67b0d [WebAssembly] Added .tabletype to asm and multiple table support in obj files
Adds more testing in basic-assembly.s and a new test tables.s.
Adds support to yaml reading and writing of tables as well.

Differential Revision: https://reviews.llvm.org/D88815
2020-10-13 07:52:23 -07:00
Sam Clegg b3b4cda104 [lld][WebAssembly] Don't GC library objects under `--whole-archive`
Followup on https://reviews.llvm.org/D85062 which ignores
entire library objects when no symbols are used within them.
This is shouldn't apply with `--whole-archive` since this
is specified to treat them like direct object inputs.

Differential Revision: https://reviews.llvm.org/D89290
2020-10-12 21:19:19 -07:00
Dan Gohman 950ae43091 [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
2020-10-12 18:54:57 -07:00
Sam Clegg 2513407d39 [lld][WebAssembly] Add support for -Bsymbolic flag
This flag works in a similar way to the ELF linker in that it
will resolve any defined symbols to their local definition with
a shared library or -pie executable.

This flag has no effect on static linking.

Differential Revision: https://reviews.llvm.org/D89152
2020-10-12 17:25:04 -07:00
Dan Gohman 6cd8511e59 [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.
2020-09-30 19:02:40 -07:00
Sam Clegg 3c45a06f26 [lld][WebAssembly] Allow exporting of mutable globals
In particular allow explict exporting of `__stack_pointer` but
exclud this from `--export-all` to avoid requiring the mutable
globals feature whenenve `--export-all` is used.

This uncovered a bug in populateTargetFeatures regarding checking
if the mutable-globals feature is allowed.

See: https://github.com/WebAssembly/binaryen/issues/2934

Differential Revision: https://reviews.llvm.org/D88506
2020-09-30 17:53:27 -07:00
Benjamin Kramer b59dff4b16 [wasm] Move WasmTraits.h to BinaryFormat
There's no dependency on Object in there and this avoids a cyclic
dependency between libMC and libObject.
2020-09-28 22:07:28 +02:00
Thomas Lively 15a5e86fb3 [lld][WebAssembly] Allow `atomics` feature with unshared memory
https://github.com/WebAssembly/threads/issues/144 updated the
WebAssembly threads proposal to make atomic operations on unshared memories
valid. This change updates the feature checking in the linker accordingly.
Production WebAssembly engines have recently been updated to allow this
behvaior, but after this change users who accidentally use atomics with unshared
memories on older versions of the engines will get validation errors at runtime
rather than link errors.

Differential Revision: https://reviews.llvm.org/D79530
2020-09-24 20:35:29 -07:00
Alexandre Ganea f2efb5742c [LLD][COFF] Cover usage of LLD-as-a-library in tests
In lit tests, we run each LLD invocation twice (LLD_IN_TEST=2), without shutting down the process in-between. This ensures a full cleanup is properly done between runs.
Only active for the COFF driver for now. Other drivers still use LLD_IN_TEST=1 which executes just one iteration with full cleanup, like before.
When the environment variable LLD_IN_TEST is unset, a shortcut is taken, only one iteration is executed, no cleanup for faster exit, like before.
A public API, lld::safeLldMain(), is also available when using LLD as a library.

Differential Revision: https://reviews.llvm.org/D70378
2020-09-24 15:07:50 -04:00
Fangrui Song 51b75b87db [lld][WebAssembly] Fix -Wunused-variable after D87663 2020-09-18 16:10:39 -07:00
Sam Clegg 3f411e9773 [lld][WebAssembly] Fix --export-all when __stack_pointer is present
With https://reviews.llvm.org/D87537 we made it an error
to import or export a mutable global with the +mutable-globals
feature present.  However the scan was of the entire symbol
table rather than just the imports or exports and the filter
didn't match exaclyt meaning the `__stack_pointer` (a mutable
global) was always triggering with error when the `--export-all`
flag was used.

This also revealed that we didn't have any test coverage for
the `--export-all` flag.

This change fixes the current breakage on the emscripten-releases
roller.

Differential Revision: https://reviews.llvm.org/D87663
2020-09-15 06:17:01 -07:00
Sam Clegg 2c12b056be [lld][WebAssembly] Allow globals imports via import_name/import_module
This feature already exists but was limited to function
symbols.

Differential Revision: https://reviews.llvm.org/D87666
2020-09-14 20:35:03 -07:00
Sam Clegg cc2da5554b [lld][WebAssembly] Add initial support for -Map/--print-map
Differential Revision: https://reviews.llvm.org/D77187
2020-09-12 16:10:51 -07:00
Sam Clegg 04febd30a8 [lld][WebAssembly] Error on import/export of mutable global without `mutable-globals` feature
Also add the +mutable-globals features in clang when
building with `-fPIC` since the linker will generate mutable
globals imports and exports in that case.

Differential Revision: https://reviews.llvm.org/D87537
2020-09-12 14:28:14 -07:00
Samuel Kostial 304264e73d [lld][WebAssembly] Emit all return types of multivalue functions
We previously were incorrectly emitting only the first result type.

Differential Revision: https://reviews.llvm.org/D85783
2020-08-12 13:14:15 -07:00
Wouter van Oortmerssen b52fc59e17 [WebAssembly] Fixed memory.init always using 64-bit ptr
(because the is64 flag was tested incorrectly in LLD).
2020-08-12 12:23:36 -07:00
Wouter van Oortmerssen 582fd474dd [WebAssembly] wasm64: fix memory.init operand types
I had assumed they would all become in i64, but this is not necessary as long as data segments stay 32-bit, see:
https://github.com/WebAssembly/memory64/blob/master/proposals/memory64/Overview.md

Differential Revision: https://reviews.llvm.org/D85552
2020-08-10 10:15:20 -07:00
Sam Clegg b34ec5969f [lld][WebAssembly] Handle weakly referenced symbols when lazy (archive) version is see first
When a weak reference of a lazy symbol occurs we were not correctly
updating the lazy symbol.  We need to tag the existing lazy symbol
as weak and, in the case of a function symbol, give it a signature.

Without the signature we can't then create the dummy function which
is needed when an weakly undefined function is called.

We had tests for weakly referenced lazy symbols but we were only
tests in the case where the reference was seen before the lazy
symbol.

See: https://github.com/WebAssembly/wasi-libc/pull/214

Differential Revision: https://reviews.llvm.org/D85567
2020-08-10 08:16:55 -07:00
Michele Scandale 53880b8cb9 [CMake] Make `intrinsics_gen` dependency unconditional.
The `intrinsics_gen` target exists in the CMake exports since r309389
(see LLVMConfig.cmake.in), hence projects can depend on `intrinsics_gen`
even it they are built separately from LLVM.

Reviewed By: MaskRay, JDevlieghere

Differential Revision: https://reviews.llvm.org/D83454
2020-07-17 16:43:17 -07:00
Wouter van Oortmerssen cc1b9b680f [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
2020-07-16 14:10:22 -07:00
Wouter van Oortmerssen 29f8c9f6c2 [WebAssembly] Triple::wasm64 related cleanup
Differential Revision: https://reviews.llvm.org/D83713
2020-07-16 12:01:10 -07:00
Wouter van Oortmerssen 4d135b0446 [WebAssembly] 64-bit memory limits 2020-07-06 12:40:45 -07:00
Sam Clegg 73e575a88e [lld][WebAssembly] Give better error message on bad archive member
Include the archive name as well as the member name when an error
is encountered parsing bitcode archives.

Differential Revision: https://reviews.llvm.org/D82884
2020-06-30 21:36:36 -07:00
Dan Gohman 46a3268312 [WebAssembly] Add warnings for -shared and -pie
The meaning of -shared and -pie are expected to be changed in the
future when Module Linking-style libraries are implemented. Begin
issuing warnings to give people a heads-up that they will be changing.

For compatibility with Emscripten, add a --experimental-pic flag which
disables these warnings.

Differential Revision: https://reviews.llvm.org/D81760
2020-06-25 15:55:46 -07:00
Wouter van Oortmerssen b9a539c010 [WebAssembly] Adding 64-bit versions of __stack_pointer and other globals
We have 6 globals, all of which except for __table_base are 64-bit under wasm64.

Differential Revision: https://reviews.llvm.org/D82130
2020-06-25 15:52:44 -07:00