In PGO, a C++ external linkage function `foo` has a private counter
`__profc_foo` and a private `__profd_foo` in a `comdat nodeduplicate`.
A `__attribute__((weak))` function `foo` has a weak hidden counter `__profc_foo`
and a private `__profd_foo` in a `comdat nodeduplicate`.
In `ld.lld a.o b.o`, say a.o defines an external linkage `foo` and b.o
defines a weak `foo`. Currently we treat `comdat nodeduplicate` as `comdat any`,
ld.lld will incorrectly consider `b.o:__profc_foo` non-prevailing. In the worst
case when `b.o:__profd_foo` is retained and `b.o:__profc_foo` isn't, there will
be dangling reference causing an `undefined hidden symbol` error.
Add SelectionKind to `Comdat` in IRSymtab and let linkers ignore nodeduplicate comdat.
Differential Revision: https://reviews.llvm.org/D106228
__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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
This adds 4 new reloc types.
A lot of code that previously assumed any memory or offset values could be contained in a uint32_t (and often truncated results from functions returning 64-bit values) have been upgraded to uint64_t. This is not comprehensive: it is only the values that come in contact with the new relocation values and their dependents.
A new tablegen mapping was added to automatically upgrade loads/stores in the assembler, which otherwise has no way to select for these instructions (since they are indentical other than for the offset immediate). It follows a similar technique to https://reviews.llvm.org/D53307
Differential Revision: https://reviews.llvm.org/D81704
Previously in the object format we punted on this and simply wrote
zeros (and didn't include the function in the elem segment). With
this change we write a meaningful value which is the segment
relative table index of the associated function.
This matches the that wasm-ld produces in `-r` mode. This inconsistency
between the output the MC object writer and the wasm-ld object
writer could cause warnings to be emitted when reading back in the
output of `wasm-ld -r`. See:
https://github.com/emscripten-core/emscripten/issues/11217
This only applies to this one relocation type which is only generated
when compiling in PIC mode.
Differential Revision: https://reviews.llvm.org/D80774
It can be used to avoid passing the begin and end of a range.
This makes the code shorter and it is consistent with another
wrappers we already have.
Differential revision: https://reviews.llvm.org/D78016
When the debug info contains a relocation against a dead symbol, wasm-ld
may emit spurious range-list terminator entries (entries with Start==0
and End==0). This change fixes this by emitting the WasmRelocation
Addend as End value for a non-live symbol.
Reviewed by: sbc100, dblaikie
Differential Revision: https://reviews.llvm.org/D74781
The changes the in-memory representation of wasm symbols such that their
optional ImportName and ImportModule use llvm::Optional.
ImportName is set whenever WASM_SYMBOL_EXPLICIT_NAME flag is set.
ImportModule (for imports) is currently always set since it defaults to
"env".
In the future we can possibly extent to binary format distingish
import which have explit module names.
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D74109
This can happen if lto::LTO::getRuntimeLibcallSymbols doesn't return
an complete/accurate list of libcalls. In this case new bitcode
object can be linked in after LTO.
For example the WebAssembly backend currently calls:
setLibcallName(RTLIB::FPROUND_F32_F16, "__truncsfhf2");
But `__truncsfhf2` is not part of `getRuntimeLibcallSymbols` so if
this symbol is generated during LTO the link will currently fail.
Without this change the linker crashes because the bitcode symbol
makes it all the way to the output phase.
See: https://bugs.llvm.org/show_bug.cgi?id=44353
Differential Revision: https://reviews.llvm.org/D71632
This is how it should've been and brings it more in line with
std::string_view. There should be no functional change here.
This is mostly mechanical from a custom clang-tidy check, with a lot of
manual fixups. It uncovers a lot of minor inefficiencies.
This doesn't actually modify StringRef yet, I'll do that in a follow-up.
Undefined symbols in WebAssembly can come with custom `import-module`
and `import-field` attributes. However when reading symbols from
bitcode object files during LTO those curtom attributes are not
available.
Once we compile the LTO object and read in the symbol table from the
object file we have access to these custom attributes. In this case,
when undefined symbols are added and a symbol already exists in the
SymbolTable we can't simple return it, we may need to update the
symbol's attributes.
Fixes: PR43211
Differential Revision: https://reviews.llvm.org/D68959
llvm-svn: 375081
Fix a bug where were not handling relocations against weakly undefined
data symbol. Add a test for this case. Also ensure that the weak
references to data symbols are not pulled in from archive files by
default (but are if `-u <name>` is added to the command line).
Fixes: PR43696
Differential Revision: https://reviews.llvm.org/D69073
llvm-svn: 375077
Debug sections are special in that they can contain relocations against
symbols that are not present in the final output (i.e. not live).
However it is also possible to have R_WASM_TABLE_INDEX relocations
against symbols that don't have a table index assigned (since they are
not address taken by actual code.
Fixes: https://github.com/emscripten-core/emscripten/issues/9023
Differential Revision: https://reviews.llvm.org/D66435
llvm-svn: 369423
When hidden symbols are discarded by comdat rules we still want to
create a local defined symbol, otherwise `Symbol::isDiscarded()` relies
on begin able to check `getChunk->discarded`.
This is a followup on rL362769. The comdat.ll test was previously GC'ing
the `__wasm_call_ctors` functions so `do_init` was not actually being
included in the link. Once that function was included in triggered the
crash bug that this change addresses.
Fixes: https://github.com/emscripten-core/emscripten/issues/8981
Differential Revision: https://reviews.llvm.org/D64872
llvm-svn: 366358
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
Fangrui Song