The macro is not needed, the same condition can also be expressed
programmatically. Its name is misleading anyway, since it has nothing to
do with the wasm64 proposal.
Drive-by: Use GraphAssembler to implement {BuildF64CopySign}.
R=jkummerow@chromium.org, tebbi@chromium.org
Bug: v8:10123, v8:10155
Change-Id: I85238172037f08bd2e4d2d4564950759524f991a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105637
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66743}
This is a reland of 2c834c5364,
in which node replacement was too aggressive.
Original change's description:
> [turbofan] Clean up ConstantFoldingReducer
>
> Change-Id: Iaf7f83cc157a6f6680da8933560347f7f3503d56
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2098736
> Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
> Commit-Queue: Georg Neis <neis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#66706}
Change-Id: I5d306092dde4119629af4c5e7e424a0e9a14310d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2106193
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66742}
There was a very narrow corner case where we would return from the
runtime function that tries to instantiate a module created by an
asm.js-to-wasm translation in an inconsistent state: returning a
Smi failure sentinel even though there is a pending exception.
Bug: chromium:1061808
Change-Id: I22f5c6cdb8d7f7abfddb2bb81dc9261c8a35bdeb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2106194
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66741}
This adjusts v8::[Shared]ArrayBuffer::NewBackingStore to allow passing
a known empty deleter -- v8::BackingStore::EmptyDeleter. Such API is
useful if the backing store memory is static or is manually managed.
We can skip adjusting the amount of external memory for ArrayBuffers
with empty deleters and thus avoid scheduling ineffective GCs.
Bug: chromium:1061960
Change-Id: I0ef5b2b0839098beb59d5cebbb28f9f81a73a042
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105355
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66740}
Port ae03752fd9
Original Commit Message:
This implements inspection of live registers on breakpoints in Liftoff.
To that end, the frame pointer of the WasmDebugBreak frame is remembered
when iterating the stack. Based on a platform-specific implementation of
{WasmDebugBreakFrameConstants}, the offset of the respective register
within that frame is computed, and the value is read from the frame.
As a drive-by, the wasm debug side table is storing register codes as
liftoff codes, which can also store register pairs (needed for i64 on
32-bit platforms, and for SIMD, which is not supported yet).
R=clemensb@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N
Change-Id: I1f4a52c349bd57098f633c5fd641642695b6fe96
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2106294
Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#66737}
Port e47f9a9d50
Original Commit Message:
The set of registers to spill was wrong. Instead of spilling wasm
parameter registers (like the WasmCompileLazy builtin), we should spill
all registers that are being used as Liftoff cache registers.
This CL defines platform-specific WasmDebugBreakFrameConstants which
hold the set of registers to spill. This set is used in the builtin, and
will later be used for inspecting the spilled registers.
In order to iterate bit sets more easily in both direction (MSB to LSB
or LSB to MSB), we add a base::bits::IterateBits{,Backwards} method
which provides the respective iterators.
R=clemensb@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N
Change-Id: Ic308a7712f080e43a0c45f496b087ce8450f657a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105563
Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#66736}
Implement all 8 extract_lane ops on ARM and ARM64.
Bug: v8:9909
Change-Id: I72e30b53c92933bd5830008ec02e1f4526e8b4c4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2103169
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66735}
At the moment when the static private method is unused
in source code (either explicitly or through eval) but is accessed
at runtime through the debugger, and there are no other potential
references to the class variable in the source code otherwise,
the reference to the class variable is lost here since the class
variable would not be context-allocated, then we could not rebuild
a proper brand check for it.
For now, a ReferenceError would be thrown and the method is considered
"optimized away", similar to how unused ordinary methods in closures
work. Before this patch it would DCHECK when generating bytecode
for the debugger instead of throwing errors.
Bug: v8:9839, v8:8330
Change-Id: I5d63131a7bdba141d01a3e6459bc27d0f5953c1a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2095637
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66734}
Implement f64x2.add, i64x2.add, i8x16.add on ARM and ARM64.
Bug: v8:9909
Change-Id: Id41bb3c02c1873e1380463264a3e5fd31949c949
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2103107
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66733}
Add safepoint mechanism to stop concurrent threads and bring them to a
safepoint. Threads are stopped before the safepoint and after e.g. the
GC resumed again. Each thread needs to be stopped in a safepoint, such
that all roots can be iterated safely.
Running threads need to be cooperative and are required to perform
regular safepoint polls.
The last version of this CL was reverted because safepoint_requested_
wasn't initialized (see https://crrev.com/c/2105634).
Bug: v8:10315
Change-Id: I6ef244c0fb31c178589b5e3d1c62687a8dd65768
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105635
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66732}
Complete Liftoff support is needed for debugging. In case of a bailout
from Liftoff, produce a better error message, also in release builds.
R=thibaudm@chromium.org
Bug: v8:10147
Change-Id: I8cdb11a5c54f9101ea611e28dd3fb7dc4fe5c538
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105633
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66730}
This reverts commit c84963eaa7.
Reason for revert: Fails on msan: https://ci.chromium.org/p/v8/builders/ci/V8%20Linux%20-%20arm64%20-%20sim%20-%20MSAN/31376
Original change's description:
> [heap] Introduce safepoint mechanism
>
> Add safepoint mechanism to stop concurrent threads and bring them to a
> safepoint. Threads are stopped before the safepoint and after e.g. the
> GC resumed again. Each thread needs to be stopped in a safepoint, such
> that all roots can be iterated safely.
>
> Running threads need to be cooperative and are required to perform
> regular safepoint polls.
>
> Bug: v8:10315
> Change-Id: I47f07e7d2ef5bc5adbba6b9e8e79a1f0f45b97ad
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2102578
> Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#66727}
TBR=ulan@chromium.org,dinfuehr@chromium.org
Change-Id: If11281b2b9fc622b91261417b202676f23f60b50
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:10315
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105634
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66729}
Add safepoint mechanism to stop concurrent threads and bring them to a
safepoint. Threads are stopped before the safepoint and after e.g. the
GC resumed again. Each thread needs to be stopped in a safepoint, such
that all roots can be iterated safely.
Running threads need to be cooperative and are required to perform
regular safepoint polls.
Bug: v8:10315
Change-Id: I47f07e7d2ef5bc5adbba6b9e8e79a1f0f45b97ad
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2102578
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66727}
The bailout was guarded by the "if (counters)" condition, which does not
make sense.
If Liftoff compilation is executed for debugging, no counters will be
passed. On platforms that do not implement Liftoff, we still need to
bail out correctly.
R=ahaas@chromium.org
Bug: v8:10147
Change-Id: I188460183bb1c376d456e0d4e54e2338f4a66e23
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105353
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66725}
Port 83ff405b1a
Original Commit Message:
Flood functions with breakpoints to prepare them for stepping. With a
small modification to the runtime function, this already implements a
basic step over functionality.
We still cannot resume, step in or step out (including stepping over a
return instruction).
R=thibaudm@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N
Change-Id: Id153b2611c528e679e8d7722e3d209fb15bcf6d1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2105055
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#66724}
Fix the test-interpreter and test-interpreter-instrinsics by adding the receiver
as an argument instead of relying on an undefined receiver.
Change-Id: I7af3216b915581155bc320b27a5454c78d04f1f5
Bug: v8:10325
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2102568
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66723}
With the current flow, it is difficult to easily get the output
of --trace-opt, --trace-deopt and --trace-osr from Android devices.
These flags log to stdout and on Android it is difficult to get this
output that preserves the formatting. This cl redirects them to a file
when --redirect-code-traces is specified.
Change-Id: I8ea1f083d0ee4577f9d70cfd2d7cb2823fd1a6c4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2089931
Commit-Queue: Mythri Alle <mythria@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66722}
This method is called in the critical section in {PublishCode}, hence
performance is important here. Since most modules will only have a
single code space anyway, we can use the main jump table in the vast
majority of cases, and avoid taking a lock and iterating another data
structure.
R=ahaas@chromium.org
Bug: v8:10330
Change-Id: I18cbd3b127172963ccc9ec576a0985e874da7865
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2104891
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66721}
This tests inspecting a bigger number of registers (covers all registers
on many platforms). It also executes all four intrinsic types (i32, i64,
f32, f64).
R=thibaudm@chromium.org
Bug: v8:10222
Change-Id: I340696d525e4001f241bb22f62f0338018ad9804
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2102575
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66720}
This implements inspection of live registers on breakpoints in Liftoff.
To that end, the frame pointer of the WasmDebugBreak frame is remembered
when iterating the stack. Based on a platform-specific implementation of
{WasmDebugBreakFrameConstants}, the offset of the respective register
within that frame is computed, and the value is read from the frame.
As a drive-by, the wasm debug side table is storing register codes as
liftoff codes, which can also store register pairs (needed for i64 on
32-bit platforms, and for SIMD, which is not supported yet).
R=jkummerow@chromium.orgCC=thibaudm@chromium.org
Bug: v8:10222
Change-Id: I01b669baf56430e100cd46cc46f210121ea679da
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2102574
Reviewed-by: Simon Zünd <szuend@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66719}
This fixes an assertion failure in mksnapshot that when the read-only
space is created for a second time, that its checksum should match the
first time it was deserialized. However with warmup scripts in
mksnapshot, the first run through doesn't deserialize it, but creates it
from scratch. Then the next time through it deserializes it which it
doesn't expect and so crashes as there is no checksum to compare it to.
This fixes it by only checking if is a last_checksum (e.g. that it was
deserialized). Additionally CHECK that we never attempt to create the
objects from scratch if previously deserialized from a snapshot.
Bug: v8:10320
Change-Id: I598e5298b68f45911e20533db91d7f24fea21045
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2102579
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66718}
This reverts commit 2c834c5364.
Reason for revert: several clusterfuzz issues, e.g. 1061805
Original change's description:
> [turbofan] Clean up ConstantFoldingReducer
>
> Change-Id: Iaf7f83cc157a6f6680da8933560347f7f3503d56
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2098736
> Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
> Commit-Queue: Georg Neis <neis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#66706}
TBR=neis@chromium.org,tebbi@chromium.org
# Not skipping CQ checks because original CL landed > 1 day ago.
Change-Id: I6e5b655bb465087a50ebaa2088795c6f920c2e51
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2104892
Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66717}
The set of registers to spill was wrong. Instead of spilling wasm
parameter registers (like the WasmCompileLazy builtin), we should spill
all registers that are being used as Liftoff cache registers.
This CL defines platform-specific WasmDebugBreakFrameConstants which
hold the set of registers to spill. This set is used in the builtin, and
will later be used for inspecting the spilled registers.
In order to iterate bit sets more easily in both direction (MSB to LSB
or LSB to MSB), we add a base::bits::IterateBits{,Backwards} method
which provides the respective iterators.
R=jkummerow@chromium.orgCC=thibaudm@chromium.org
Bug: v8:10222
Change-Id: I73ecbdff9b29e244c478b404063c0c9ee25bc821
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2102570
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66715}
This change is motivated by SpiderMonkey's policy against bare
new/delete. (I also think it's just a nicer way to write this.)
R=jgruber@chromium.org
here is the same as the change I made in the equivalent SM code.
Note: I'm not importing regexp.cc into SpiderMonkey, but the change
Bug: v8:10303
Change-Id: I3c81727eb7dea9c0ec78241e3c82ffc9e7007827
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2091858
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66713}
Based on feedback in https://github.com/WebAssembly/simd/issues/189 and
inspired by cranelift's codegen, we reduce instruction count by 1 for
both types of operations - all_true goes from 6 -> 5, any_true from 4 ->
3. The main transformation is to change a sequence of movq + ptest +
cmovq to ptest + setcc. We unfortunately cannot cut down the instruction
counts further, since we need to zero the destination register.
Change-Id: Idc2540dbec755c7a7ff5069955f74e978190161d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2100994
Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66710}
This CL extracts a function which reads from a buffer and additionally
increments an offset for the next read.
R=clemensb@chromium.org
Bug: v8:10281, v8:10155
Change-Id: Id8d79130cde17053d701d2508e40cba993471e55
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2101001
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66707}
Doing the bounds check in C++ has the advantage that we generate less
code, and that TurboFan graphs get smaller. Additionally it will make
code generation from Liftoff easier. There is not really a downside:
We already called C++ anyways to do the actual memory.fill operation.
R=clemensb@chromium.org
Bug: v8:10281
Change-Id: If4e36d45a3fd1c4c0fef9137d37097a012e7a409
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2100991
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66703}
to properly choose named or indexed mode
Bug: chromium:1059738
Change-Id: Icd086fee31079f52770742afa54fc946acb1fd81
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2101005
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66702}
SignatureHelper::kMarker needs an explicit instantiation after
f3b4167f8b.
Change-Id: Ia5a0696a576a2c59bea262359058bd63eb3c8426
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2101004
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66701}
This CL adds memory masking to our implementation of memory.copy and
memory.init when spectre mitigations are enabled.
R=clemensb@chromium.org
Bug: v8:10281
Change-Id: I8722fa7ab244f339d859d5479eceede85dbbd08c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2100990
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66700}
Port f3b4167f8bhttps://crrev.com/c/2091471
Original Commit Message:
In preparation for adding reference types, which need an additional
parameter to indicate the referenced type.
Change-Id: I1b66bffea3ac2637886673476c8f7d62150b33a3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2100695
Auto-Submit: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66699}
Flood functions with breakpoints to prepare them for stepping. With a
small modification to the runtime function, this already implements a
basic step over functionality.
We still cannot resume, step in or step out (including stepping over a
return instruction).
R=clemensb@chromium.org
Bug: v8:10321
Change-Id: Ia4a6335d24c1a511c2f1fc9b48d728f327b3df56
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2098732
Reviewed-by: Simon Zünd <szuend@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66697}
In debug builds of Liftoff, the opcode of the next instruction is
printed as a code comment. For multi-byte opcodes, all but the first
byte have to be extracted explicitly from the wasm code in the
{NextInstruction} function. The bounds check for this extraction was
missing.
R=clemensb@chromium.org
Bug: chromium:1061304
Change-Id: I16a05d54e50506c1387970ad84082d7e76108fc0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2100996
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66696}
The {TYPE_CHECK} macro used an ancient pattern to check for
assignability, by assigning to a static_casted nullptrs of the
respective types.
C++11 introduced standard library helpers to express this more
naturally. The most direct translation would have been to use
{std::is_assignable} or {std::is_convertible} on the pointer types, but
in most cases we can be even more strict and force one type to be a
proper subtype of the other.
The only exception is {ReturnValue}, which allows to assign anything if
it's void.
R=ulan@chromium.org
Bug: v8:10155
Change-Id: I41c1103e0206514c8700c47a0bf107ad704cfc47
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2093497
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66695}
