Improve the `fallThroughScope` computation, in order to handle calls to
`NoReturn` functions in the analysis, representing the fact that they
induce a `noFallthrough` scope (i.e., execution will not ever resume
after the call, and therefore we can later improve the nesting of the
code with the `promoteNoFallthrough` pass).
We introduce a simplification step, which looks for `switch`es that can
be reduced to simpler `if` statements.
Specifically, the logic is the following:
1) When we identify a `switch` statement composed by a single `case` and
a possible default, we transform it into an `if` with the `case` now
corresponding to the `then`, and the `default` corresponding to the
`else`, if present.
2) When we identify a `switch` statement composed by two `case`s, and no
`default` is present, we can promote it to an `if` with `then` `else`
branches.
Other key details:
- The promotion happens only if we can identify at least one of the
`case`s that have a single element in the `case` label. If this is not
the case, we do not promote one to RHS of the `if` condition.
- A new `CompareNode` class, inheriting from `ExprNode`, is created, in
order to represent the equality or inequality condition of an `IfNode`
instance that is the result of the promotion. This `CompareNode` can
represent for the LHS both an `llvm::Value` or the `loop_state_var`,
while it embeds the RHS constant which completes the comparison.
- We remove `SwitchBreak` AST nodes that may now appear as children of
an `if` node promoted from a `switch`.
- We introduce in the `CompareNode` the `weaved` concept. Indeed, if a
promotion of a weaved `switch` happens, we should avoid the
serialization of the instructions leading to the computation of the
condition of the original `switch`, because they have been already
emitted by the main related dominating `switch`.
We also introduce an additional simplification step, which takes care
of:
- Promoting `!(==)` to `(!=)` and `!(!=)` to `(==)`, if the inner
equal/not equal is represented via a `CompareNode`.
- Promoting `x == 0` to `!x` and `x != 0` to `x`.
To be able to correctly emit (or not) the instructions computing a
condition of an `IfNode`, we need to add the `EmittBB` flag, an
additional parameter to the `buildGHASTCondition` function, which
controls the emission of the statements of a basic block computing a
condition.
Consequently, the `IfNode` acquires a `IsWeaved` field, which is used to
mirror the property having the same name on `SwitchNode`. Being now
possible a promotion from a dual `SwitchNode` to an `IfNode`, we need to
represent this property on the `IfNode` too.
The `default` `case` is now a standard `case`, and it is identified only
by having the `label` set empty.
Therefore, a list of beautify and transformation actions now do not need
special casing in order to handle the `default` `case`, which is reached
during the standard iteration over the `case`s.
A special accessor is still necessary, in order to correctly emit the
`default` `case` in the backend.
Introduce implicit statements simplification phase, specifically:
- A implicit `return` simplification: `return` statements in `void`
type functions, which are not followed by any other scope, can be
omitted.
- A implicit `continue` simplification: `continue` statements whose
fallthrough leads directly to the end of the cycle scope (i.e., to
execute another iteration of the enclosing loop), can be omitted.
In order to avoid the printing of the implicit `return`, we need an
additional `emitReturn` parameter in the `emitBasicBlock` method of the
`CCodeGenerator` class.
Now, also `break` and `continue` on the AST, when printed, have the ID
number of the `ASTNode`, and in the name they preserve the original
`CFGNode` one also.
This commit reorders the argument passed to various `printDeclaration`
and `printDefinition` helper functions, to make them more uniform across
each other, and to accept the same arguments in the same order.
Improve the logic of the first iteration outline:
1) The cloning of the nodes involved in the first iteration outlining,
is now performed with a series of DFS visits from all the late entry
nodes in the `MetaRegion`, instead of performing a blind clone of all
the nodes and removing those not needed.
2) Restoring the edges between the cloned nodes has been subject to
minor changes.
3) The outline nodes are now assigned to a `MetaRegion` using a new
logic, instead of blindly assigning them to the parent `MetaRegion`.
We now explicitly store the retreatings edges, that will eventually be
connected to the `continue` nodes, so that we can explicitly handle
them, without resorting to iterating over the predecessors of the
`EntryNode`, which although correct is a fragile method with respect to
defective situations.
In addition, we check that after the restructuring, all the retreating
edges that we connect to `continue` nodes, do point to the `EntryNode`
before the transformation.
We now implement the `nodesBetween` primitive with a double DFS visit.
Specifically, we have:
1) A forward DFS that starts from the `Source`, and stops at `Target`.
2) A backward DFS that starts from the `Target`, and stops at `Source`.
The final result is then the intersection of the nodes found by the two
above DFS visits.
A new `findReachableNodes` primitive is also added to perform a DFS from
a `Source` node, which stops at the `Stop` parameter node, if present.
Added unit tests to improve the coverage.
- Add PrepareLLVMIRForMLIR Pass.
This Pass performs massaging of the LLVM IR
produced by revng so it can be parsed/accepted
for the LLVM MLIR Dialect.
- Introduce new pipeline branch: llvmir-to-mlir.yml.
- Add LLVMIRToMLIR step.
- Add ImportLLVMToMLIRPipe pipe.
This commit sets a name for types we use in OpaqueExtractValues.
These are StructTypes that can only be returned from isolated functions
with RawFunctionType prototype on the model, or from helpers that do not
represent isolated functions.
The name is required because when we will converto to MLIR LLVM Dialect,
there are checks in place that forbid unnamed types.
The code re-uses code that is used to print C code, in order to make
sure that the struct names we use for this are the same as those we emit
in C, to ease debugging.
This commit also cleans up the unittest to make it more concise, while
still testing the same things.
Add the PipelineDescription object that describes the structure of a
pipeline. This will be used by all the downstream users instead of
pipeline accessor methods via PipelineC.
Giacomo Vercesi