In this PR, the classes that represent the adjust branch weights
transformation and fuzzer pass were implemented. This transformation
adjusts the branch weights of a OpBranchConditional instruction.
The fact manager maintains an equivalence relation on data descriptors
that tracks when one data descriptor could be used in place of
another. An algorithm to compute the closure of such facts allows
deducing new synonym facts from existing facts. E.g., for two 2D
vectors u and v it is known that u.x is synonymous with v.x and u.y is
synonymous with v.y, it can be deduced that u and v are synonymous.
The closure computation algorithm is very expensive if we get large
equivalence relations.
This change addresses this in three ways:
- The size of equivalence relations is reduced by limiting the extent
to which the components of a composite are recursively noted as
being equivalent, so that when we have large synonymous arrays we do
not record all array elements as being pairwise equivalent.
- When computing the closure of facts, equivalence classes above a
certain size are simply skipped (which can lead to missed facts)
- The closure computation is performed less frequently - it is invoked
explicitly before fuzzer passes that will benefit from data synonym
facts. A new transformation is used to control its invocation, so
that fuzzing and replaying do not get out of sync.
The change also tidies up the order in which some getters are declared
in FuzzerContext.
(1) Runtime arrays are turned into fixed-size arrays, by turning
OpTypeRuntimeArray into OpTypeArray and uses of OpArrayLength into
uses of the constant used for the length of the fixed-size array.
(2) Atomic instructions are not donated, and uses of their results are
replaced with uses of constants of the result type.
In this PR, the classes that represent the toggle access chain
instruction transformation and fuzzer pass were implemented. This
transformation toggles the instructions OpAccessChain and
OpInBoundsAccessChain between them.
Fixes#3193.
This introduces a new fuzzer pass to add instructions to the module
that define equations, and support in the fact manager for recording
equation facts and deducing synonym facts from equation facts.
Initially the only equations that are supported involve OpIAdd,
OpISub, OpSNegate and OpLogicalNot, but there is scope for adding
support for equations over various other operators.
This change adds a fuzzer pass that sprinkles access chain
instructions into a module at random. This allows other passes to
have a richer set of pointers available to them, in particular the
passes that add loads and stores.
Adds a fuzzer pass that inserts function calls into the module at
random. Calls from dead blocks can be arbitrary (so long as they do
not introduce recursion), while calls from other blocks can only be to
livesafe functions.
The change fixes some oversights in transformations to replace
constants with uniforms and to obfuscate constants which testing of
this fuzzer pass identified.
This change ensures that global and local variables donated from other
modules are always initialized at their declaration in the module
being transformed. This is to help limit issues related to undefined
behaviour that might arise due to accessing uninitialized memory.
The change also introduces some helper functions in fuzzer_util to
make it easier to find the pointee types of pointer types.
This change adds fuzzer passes that sprinkle loads and stores into a
module at random, with stores restricted to occur in either dead
blocks, or to use pointers for which it is known that the pointee
value does not influence the module's overall behaviour.
The change also generalises the VariableValueIsArbitrary fact to
PointeeValueIsIrrelevant, to allow stores through access chains or
object copies of variables whose values are known to be irrelevant.
The change includes some other minor refactorings.
Adds two new fuzzer passes to add variables to a module: one that adds
Private storage class global variables, another that adds Function
storage class local variables.
This change adds a new kind of fact to the fact manager, which records
when a variable (or pointer parameter) refers to an arbitrary value,
so that anything can be stored to it, without affecting the observable
behaviour of the module, and nothing can be guaranteed about values
loaded from it. Donated modules are the current source of such
variables, and other transformations, such as outlining, have been
adapted to propagate these facts appropriately.
This change allows the generator to (optionally and at random) make
the functions of a module "livesafe" during donation. This involves
introducing a loop limiter variable to each function and gating the
number of total loop iterations for the function using that variable.
It also involves eliminating OpKill and OpUnreachable instructions
(changing them to OpReturn/OpReturnValue), and clamping access chain
indices so that they are always in-bounds.
This adds a new kind of fact to the fact manager that knows whether a
block is dead - i.e. guaranteed to be statically unreachable - and a
new transformation for adding a selection construct to a CFG that
conditionally branches to a fresh, dead block, such that the branch
will never be dynamically taken. Transformations that may create new
blocks ('split block' and 'outline function') are updated to propagate
dead block facts to newly-created blocks where appropriate. A fuzzer
pass randomly adds dead blocks to the module.
Future transformations will be able to exploit the fact that such
blocks are known to be dead.
A new transformation and associated fuzzer pass in spirv-fuzz that
selects single-entry single-exit control flow graph regions and for
each selected region outlines the region into a new function and
replaces the original region with a call to this function.
Prior to this change, TransformationReplaceIdWithSynonym was designed
to be able to replace an id with some synonymous data descriptor,
possibly necessitating extracting from a composite into a fresh id in
order to get at the synonymous data. This change simplifies things so
that TransformationReplaceIdWithSynonym just allows one id to be
replaced by another id. It is the responsibility of the associated
fuzzer pass - FuzzerPassApplyIdSynonyms - to perform the extraction
operations, using e.g. TransformationCompositeExtract.
Inroduces a new transformation that adds a vector shuffle instruction
to the module, with associated facts about how the result vector of
the shuffle relates to the input vectors.
A fuzzer pass to add such transformations is not yet in place.
This change fixes a bug in EquivalenceRelation, changes the interface
of EquivalenceRelation to avoid exposing (potentially
nondeterministic) unordered sets, and changes the interface of
FactManager to allow querying data synonyms directly. These interface
changes have required a lot of corresponding changes to client code
and tests.
At present, TransformationReplaceIdWithSynonym both extracts elements
from composite objects and replaces uses of ids with synonyms. This
new TransformationCompositeExtract class will allow that
transformation to be broken into smaller transformations.
Class TransformationConstructComposite has been renamed to
TransformationCompositeConstruct, to correspond to the name of the
SPIR-V instruction (as is done with e.g. TransformationCopyObject).
Running tests revealed an issue related to checking dominance in
TransformationReplaceIdWithSynonym, which is also fixed here.
This change uses the recently-added equivalence relation class to
re-work the way synonyms between data values are managed by the fact
manager.
The tests for 'transformation_replace_id_with_synonym' have been
temporarily removed. This is because those tests are going to be
split into a number of test classes in an upcoming PR, once some other
refactorings have been applied, and it would be burdensome to
temporarily refactor all the tests to be in a working state for this
intermediate change.
A new pass that gives spirv-fuzz the ability to adjust the memory
operand masks associated with memory access instructions (such as
OpLoad and OpCopy Memory).
Fixes#2940.
This change refactors the 'split blocks' transformation so that an
instruction is identified via a base, opcode, and number of those
opcodes to be skipped when searching from the base, as opposed to the
previous design which used a base and offset.
A refactoring that separates the identification of an instruction from
the identification of a use in an instruction, to enable the former to
be used independently of the latter.
