This commit drops calls to `_init_$CPU_STATE` for non-general purpose
registers. Instead, these part of the CPU state are initialized using
the initializer of the CSV, which is in turn provided by QEMU.
This enables us to properly initialize as appropriate fields such as
x86-64's DF flag.
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.
When copying nodes from nested AST to the root one, we should take care
of overwriting the mapping between the old `OldCFGNode`, so that it now
points to the newer AST node representing it.
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.
After the changes to the direction `CrossRelation` output is parsed,
the slicer wasn't updated accordingly. Because of that, the slices were
as if they were produced backwards.
As for the full graph, since it starts from an artificially added node
that doesn't have any successors by definition - it was appearing empty
(only the non-emittable "root" node was present).
This also changes the names that show up in the VSCode-based UI, so that
they are coherent with what's included in the decompiled C code via the
related #include directives.
Before this commit, the `printDefinition` helper functions for
`StructType` and `UnionType` were printing a duplicated whitespace when
generating the inline type definition as part of the declaration of a
field of a struct or union.
This commit skips the redundant whitespace when relevant.
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.
Before this commit, DLA's backend often emitted things like:
```c
struct x {
struct y {
int32_t z;
uint8_t padding[4];
} _offset_0;
uint8_t padding[8];
};
```
This is suboptimal, since the fields of y actually can just be inlined
into x, giving:
```c
struct x {
int32_t z;
uint8_t padding[12];
};
```
This behaviour was due to a logic bug carried over from old versions of
the code, and partially extended, but never revisited nor thought
through.
This commit fixes the problem, making the second behaviour the only
thing DLA ever does when updating the model.
Basically, struct fields are copied over field by field, instead of
inserting the bulk struct (y in the example) inside the larger struct to
update (x in the example).
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`.
Remove old broken code that handled `Set` nodes as source of retreatings
when inserting an `entry` dispatcher. This situation should no longer be
the case, because a `Set` node should not be the `source` of a
retreating edge. We assert this situation.
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.
Before this commit, the code was using an old arcane algorithm that was
adding and removing dummy frontier nodes, and relying on the
DominatorTree.
This commit drops the DominatorTree altogether, drops the use of
frontier nodes, and rewrites the algorithm only using successors and
predecessors.
Now a node outside a metaregion M is included in the metaregion only if
all its predecessors are part of the metaregion, and none of them is
already in another metaregion that is a transitive parent of M.
Before this commit, the whole body of each loop was outlined and
duplicated, only to be removed later if not necessary.
Now we only do this if there is more than one entry to the loop, which
is the simplest condition to detect when first iteration outlining is
needed.
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.
Its presence lead to an undesirable situation where the file itself
would get copied to the install directory and using `add_subdirectory`
led to creating a set of support files (which would get installed too).
Simple solution: just push the content of that file in the root
`CMakeLists.txt`.
Alessandro Di Federico