The extension SPV_KHR_maximal_reconvergence adds more constraints
around the merge blocks, and how the control flow can be altered.
The one we address here is explained in the following part of the spec:
Note: This means that the instructions in a break block will execute as if
they were still diverged according to the loop iteration. This restricts
potential transformations an implementation may perform on the IR to match
shader author expectations. Similarly, instructions in the loop construct
cannot be moved into the continue construct unless it can be proven that
invocations are always converged.
Until the optimizer is clever enough to determine if the invocation
have already converged, we shall not meld a block which branches to a
merge block into it, as it might move some instructions outside of the
convergence region.
This behavior being only required with the extension, this commit
behavior change is gated by the extension.
This means using wave operations without the maximal reconvergence
extension might lead to undefined behaviors.
Co-authored-by: Natalie Chouinard <chouinard.nm@gmail.com>
Constexpr guaranteed no runtime init in addition to const semantics.
Moving all opt/ to constexpr.
Moving all compile-unit statics to anonymous namespaces to uniformize
the method used (anonymous namespace vs static has the same behavior
here AFAIK).
Signed-off-by: Nathan Gauër <brioche@google.com>
Fixes#4918
* Prevent block merging from producing an invalid case construct by
merging a switch target/default with another construct's merge or
continue block
* This is to satisfy the structural dominance requirement between the
switch header and the case constructs
Debug[No]Line are tracked and optimized using the same mechanism that tracks
and optimizes Op[No]Line.
Also:
- Fix missing DebugScope at top of block.
- Allow scalar replacement of access chain in DebugDeclare
This change allows the reducer to merge together blocks even when they
are unreachable, but keeps the restriction of reachability in place
for the optimizer.
Fixes#4302.
There was a lot of code in the codebase that would get the dominator
analysis for a function and then use it to check whether a block is
reachable. In the fuzzer, a utility method had been introduced to make
this more concise, but it was not being used consistently.
This change moves the utility method to IRContext, so that it can be
used throughout the codebase, and refactors all existing checks for
block reachability to use the utility method.
As explained in #3118, spirv-opt merge-blocks pass causes a
spirv-val error when an OpBranch has an OpLine in front of it.
OpLoopMerge
OpBranch ; Will be killed by merge-blocks pass
OpLabel ; Will be killed by merge-blocks pass
OpLine ; will be placed between OpLoopMerge and OpBranch - error!
OpBranch
To fix this issue, this commit moves line info of OpBranch to
OpLoopMerge.
Fixes#3118
* Validate that if a construct contains a header and it's merge is
reachable, the construct also contains the merge
* updated block merging to not merge into the continue
* update inlining to mark the original block of a single block loop as
the continue
* updated some tests
* remove dead code
* rename kBlockTypeHeader to kBlockTypeSelection for clarity
* Fixes#2338. Added check for phi node before merging blocks.
* Added functionality to merge blocks A and B even when B starts with OpPhi instructions, by replacing uses of the OpPhi results with the definitions coming from A. Added some tests for this.
* Fixed assertion.
