* Update fuzz tests to not use invalid combinations of LoopMerge + BranchConditional
New IDs were selected to make clear the transformation being done here, instead
of reordering all IDs in between or refactoring the SPIR-V in the test.
* spirv-val: Conditional Branch without an exit is invalid in loop header
From 2.16.2, for CFG:
Selections must be structured. That is, an OpSelectionMerge
instruction is required to precede:
- an OpSwitch instruction
- an OpBranchConditional instruction that has different True Label
and False Label operands where neither are declared merge blocks
or Continue Targets.
This fixes a problem where TransformationInlineFunction could lead to
distinct instructions having identical unique ids. It adds a validity
check to detect this problem in general.
Fixes#3911.
Adds a virtual method, GetFreshIds(), to Transformation. Every
transformation uses this to indicate which ids in its protobuf message
are fresh ids. This means that when replaying a sequence of
transformations the replayer can obtain a smallest id that is not in
use by the module already and that will not be used by any
transformation by necessity. Ids greater than or equal to this id
can be used as overflow ids.
Fixes#3851.
TransformationContext now holds a std::unique_ptr to a FactManager,
rather than a plain pointer. This makes it easier for clients of
TransformationContext to work with heap-allocated instances of
TransformationContext, which is needed in some upcoming work.
Some transformations (e.g. TransformationAddFunction) rely on running
the validator to decide whether the transformation is applicable. A
recent change allowed spirv-fuzz to take validator options, to cater
for the case where a module should be considered valid under
particular conditions. However, validation during the checking of
transformations had no access to these validator options.
This change introduced TransformationContext, which currently consists
of a fact manager and a set of validator options, but could in the
future have other fields corresponding to other objects that it is
useful to have access to when applying transformations. Now, instead
of checking and applying transformations in the context of a
FactManager, a TransformationContext is used. This gives access to
the fact manager as before, and also access to the validator options
when they are needed.
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.
Because dominance information becomes a bit unreliable when blocks are
unreachable, this change makes it so that the 'dead break'
transformation will not introduce a break to an unreachable block.
Fixes#2907.
The implementation of these passes had overlooked the fact that adding
a new edge to a control flow graph can change dominance information.
Adding a dead break/continue risks causing uses to no longer be
dominated by their definitions. This change introduces various tests
to expose such scenarios, and augments the preconditions for these
transformations with checks to guard against the situation.
