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 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.
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
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
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
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
This reverts commit 418df4a6ab.
This change broke emscripten tests, I believe because it started
generating 5-byte a wide table index in the call_indirect instruction.
Neither v8 nor wabt seem to be able to handle that. The spec
currently says that this is single 0x0 byte and:
"In future versions of WebAssembly, the zero byte occurring in the
encoding of the call_indirectcall_indirect instruction may be used to
index additional tables."
So we need to revisit this change. For backwards compat I guess
we need to guarantee that __indirect_function_table is always at
address zero. We could also consider making this a single-byte
relocation with and assert if have more than 127 tables (for now).
Differential Revision: https://reviews.llvm.org/D95005
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
This patch changes to make call_indirect explicitly refer to the
corresponding function table, residualizing TABLE_NUMBER relocs against
it.
With this change, wasm-ld now sees all references to tables, and can
link multiple tables.
Differential Revision: https://reviews.llvm.org/D90948
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
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
Local values are constants or addresses that can't be folded into
the instruction that uses them. FastISel materializes these in a
"local value" area that always dominates the current insertion
point, to try to avoid materializing these values more than once
(per block).
https://reviews.llvm.org/D43093 added code to sink these local
value instructions to their first use, which has two beneficial
effects. One, it is likely to avoid some unnecessary spills and
reloads; two, it allows us to attach the debug location of the
user to the local value instruction. The latter effect can
improve the debugging experience for debuggers with a "set next
statement" feature, such as the Visual Studio debugger and PS4
debugger, because instructions to set up constants for a given
statement will be associated with the appropriate source line.
There are also some constants (primarily addresses) that could be
produced by no-op casts or GEP instructions; the main difference
from "local value" instructions is that these are values from
separate IR instructions, and therefore could have multiple users
across multiple basic blocks. D43093 avoided sinking these, even
though they were emitted to the same "local value" area as the
other instructions. The patch comment for D43093 states:
Local values may also be used by no-op casts, which adds the
register to the RegFixups table. Without reversing the RegFixups
map direction, we don't have enough information to sink these
instructions.
This patch undoes most of D43093, and instead flushes the local
value map after(*) every IR instruction, using that instruction's
debug location. This avoids sometimes incorrect locations used
previously, and emits instructions in a more natural order.
In addition, constants materialized due to PHI instructions are
not assigned a debug location immediately; instead, when the
local value map is flushed, if the first local value instruction
has no debug location, it is given the same location as the
first non-local-value-map instruction. This prevents PHIs
from introducing unattributed instructions, which would either
be implicitly attributed to the location for the preceding IR
instruction, or given line 0 if they are at the beginning of
a machine basic block. Neither of those consequences is good
for debugging.
This does mean materialized values are not re-used across IR
instruction boundaries; however, only about 5% of those values
were reused in an experimental self-build of clang.
(*) Actually, just prior to the next instruction. It seems like
it would be cleaner the other way, but I was having trouble
getting that to work.
This reapplies commits cf1c774d and dc35368c, and adds the
modification to PHI handling, which should avoid problems
with debugging under gdb.
Differential Revision: https://reviews.llvm.org/D91734
A struct in C passed by value did not get debug information. Such values are currently
lowered to a Wasm local even in -O0 (not to an alloca like on other archs), which becomes
a Target Index operand (TI_LOCAL). The DWARF writing code was not emitting locations
in for TI's specifically if the location is a single range (not a list).
In addition, the ExplicitLocals pass which removes the ARGUMENT pseudo instructions did
not update the associated DBG_VALUEs, and couldn't even find these values since the code
assumed such instructions are adjacent, which is not the case here.
Also fixed asm printing of TIs needed by a test.
Differential Revision: https://reviews.llvm.org/D94140
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
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
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
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
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
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
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
This reverts commit cf1c774d6a.
This change caused several regressions in the gdb test suite - at least
a sample of which was due to line zero instructions making breakpoints
un-lined. I think they're worth investigating/understanding more (&
possibly addressing) before moving forward with this change.
Revert "[FastISel] NFC: Clean up unnecessary bookkeeping"
This reverts commit 3fd39d3694.
Revert "[FastISel] NFC: Remove obsolete -fast-isel-sink-local-values option"
This reverts commit a474657e30.
Revert "Remove static function unused after cf1c774."
This reverts commit dc35368ccf.
Revert "[lldb] Fix TestThreadStepOut.py after "Flush local value map on every instruction""
This reverts commit 53a14a47ee.
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
Local values are constants or addresses that can't be folded into
the instruction that uses them. FastISel materializes these in a
"local value" area that always dominates the current insertion
point, to try to avoid materializing these values more than once
(per block).
https://reviews.llvm.org/D43093 added code to sink these local
value instructions to their first use, which has two beneficial
effects. One, it is likely to avoid some unnecessary spills and
reloads; two, it allows us to attach the debug location of the
user to the local value instruction. The latter effect can
improve the debugging experience for debuggers with a "set next
statement" feature, such as the Visual Studio debugger and PS4
debugger, because instructions to set up constants for a given
statement will be associated with the appropriate source line.
There are also some constants (primarily addresses) that could be
produced by no-op casts or GEP instructions; the main difference
from "local value" instructions is that these are values from
separate IR instructions, and therefore could have multiple users
across multiple basic blocks. D43093 avoided sinking these, even
though they were emitted to the same "local value" area as the
other instructions. The patch comment for D43093 states:
Local values may also be used by no-op casts, which adds the
register to the RegFixups table. Without reversing the RegFixups
map direction, we don't have enough information to sink these
instructions.
This patch undoes most of D43093, and instead flushes the local
value map after(*) every IR instruction, using that instruction's
debug location. This avoids sometimes incorrect locations used
previously, and emits instructions in a more natural order.
This does mean materialized values are not re-used across IR
instruction boundaries; however, only about 5% of those values
were reused in an experimental self-build of clang.
(*) Actually, just prior to the next instruction. It seems like
it would be cleaner the other way, but I was having trouble
getting that to work.
Differential Revision: https://reviews.llvm.org/D91734
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
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
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
This test was checking behaviour that only exists in the debug
configuration so will fail in release builds.
Perhaps there is way to keep this test around and only run
it in debug builds but for now I'm removing so fix the
release builders.
Differential Revision: https://reviews.llvm.org/D90542
Andy Wingo