These changes were originally submitted separately on different days,
and a major performance regression was seen after the first change
when creating snapshots that led to both being reverted. However,
that performance regression should be addressed by the followup.
First change:
"[vm] Treat the dispatch table as a root in the snapshot.
Additional changes:
* Only serialize a dispatch table in precompiled snapshots.
* Add information in v8 snapshot profiles for the dispatch table.
* Fix a typo in a field name.
* Print the number of Instructions objects (or payloads, for
precompiled bare instructions mode) in the fake cluster for
the data section.
* Fix v8 snapshots profiles so objects in memory mapped segments
and only those are prefixed with "(RO) ".
* Add names for Instructions objects in v8 snapshot profiles
when we can use the assembly namer.
* Add command line flag for old #define'd false flag."
Second change:
"[vm/aot] Keep GC-visible references to dispatch table Code entries.
This change splits dispatch table handling into four distinct
parts:
* The dispatch table generator does not make a dispatch table
directly, but rather creates an Array that contains the Code
objects for dispatch table entries.
* The precompiler takes this Array and puts it in the object
store, which makes it a new GC root.
* The serializer takes this information and serializes the
dispatch table information in the same form as before.
* The deserializer creates a DispatchTable object and populates
it using the serialized information.
The change in the precompiler ensures that the Code objects
used in the dispatch table have GC-visible references. Thus,
even if all other references to them from the other GC roots
were removed, they would be accessible in the serializer in
the case of a GC pass between the precompiler and serializer.
This change also means that the serializer can retrieve and
trace the Code objects directly rather than first looking up
the Code objects by their entry point."
Bug: https://github.com/dart-lang/sdk/issues/41022
Change-Id: I52c83b0536fc588da0bef9aed1f0c72e8ee4663f
Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-release-x64-try,vm-kernel-precomp-linux-release-simarm-try,vm-kernel-precomp-linux-release-simarm64-try,vm-kernel-precomp-linux-release-simarm_x64-try,vm-kernel-precomp-android-release-arm64-try,vm-kernel-precomp-android-release-arm_x64-try,vm-kernel-precomp-mac-release-simarm64-try,vm-kernel-precomp-win-release-x64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/139285
Commit-Queue: Teagan Strickland <sstrickl@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
This change splits dispatch table handling into four distinct
parts:
* The dispatch table generator does not make a dispatch table
directly, but rather creates an Array that contains the Code
objects for dispatch table entries.
* The precompiler takes this Array and puts it in the object
store, which makes it a new GC root.
* The serializer takes this information and serializes the
dispatch table information in the same form as before.
* The deserializer creates a DispatchTable object and populates
it using the serialized information.
The change in the precompiler ensures that the Code objects
used in the dispatch table have GC-visible references. Thus,
even if all other references to them from the other GC roots
were removed, they would be accessible in the serializer in
the case of a GC pass between the precompiler and serializer.
This change also means that the serializer can retrieve and
trace the Code objects directly rather than first looking up
the Code objects by their entry point.
Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-release-x64-try,vm-kernel-precomp-linux-release-simarm-try,vm-kernel-precomp-linux-release-simarm64-try,vm-kernel-precomp-linux-release-simarm_x64-try,vm-kernel-precomp-android-release-arm64-try,vm-kernel-precomp-android-release-arm_x64-try,vm-kernel-precomp-mac-release-simarm64-try,vm-kernel-precomp-win-release-x64-try
Change-Id: Ic9ba29dfd64945a6e9a51f9de73f74d9202b58b7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/138288
Commit-Queue: Teagan Strickland <sstrickl@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Aske Simon Christensen <askesc@google.com>
NullCheck pc descriptors are added to all dispatch table calls where the
receiver may be null (and the selector is not one implemented by null).
All null entries in the table go to the NullError runtime entry, which
reads the NullCheck pc descriptor to get the name of the called member
for the error message.
Change-Id: I9d2847d0ccdfdb735b06e879916920ec299f39bc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/134294
Commit-Queue: Aske Simon Christensen <askesc@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
This is a Dart-tailored implementation of the "row-displacement
dispatch table" technique for closed-world instance calls:
All interface targets in the program are grouped into selectors such
that all targets that could potentially be called from the same call
site have the same selector (currently just grouped by name).
Each selector is assigned a selector offset such that offset + classid
is unique for all selector/classid combinations where the class
implements the selector.
At every instance call site that has an interface target (i.e. where
the static type of the receiver is not dynamic), the selector offset +
receiver classid is computed and used as index into a global table of
entry points.
If the receiver can be null (as determined by the front-end TFA and the
VM type propagation), a null check is inserted before the call.
An arguments descriptor is provided (only) for selectors that need it
(those which have type parameters or optional/named parameters).
The dispatch table calls don't need the monomorphic entry code, so for
functions that are only called via dispatch table calls (i.e. never
called dynamically), the monomorphic entry code is left out.
Some future improvements to the table dispatch implementation are
mentioned in https://github.com/dart-lang/sdk/issues/40188
The table dispatch flag is disabled by default in this commit. A
separate commit enables the flag.
Change-Id: Ic2911742b4a2c9a8d3bc7df60605454cbe4c0714
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/126648
Commit-Queue: Aske Simon Christensen <askesc@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Teagan Strickland