This commit drops some old broken code that was a leftover from when
MarkAssignments didn't inject calls to Assign, and that was poorly
migrated to Assign, causing it to be dead code.
This commit fixes a bug in the hasSideEffects function, used to evaluate
if an ExprNode has side effects.
Before this commit, when calling hasSideEffects on a NotNode, the
return value was true if the operand of NotNode **did not** have side
effects, which is wrong.
This commit changes the behaviour so that a NotNode has side effects if
and only if its only operand has side effects.
This commit fixes a bug in the hasSideEffects function, used to evaluate
if an ExprNode has side effects.
Before this commit, when calling hasSideEffects on an AndNode, the
return value was true if **both** the LHS and RHS of the AndNode had
side effects, which is wrong.
This commit changes the behaviour so that if **either** LHS **or** the
RHS of the And have any side effect, than hasSideEffects returns true
for the And.
Before this commit, the simplifyShortCircuit beautifier did not recur on
the then/else branch of an IfNode, basically stopping recursion very
early and potentially missing a lot of beautification opportunities.
Introduce the hybrid beautifier aiming to simplify double `not`s (one on
the IR side (e.g., a `icmp ne`), and one on the `ExprNode` side on the
`GHAST` in the form of a `NotNode`.
To do this hybrid beautifier, we basically need to do the following:
- Implement a preliminary collection phase which computes which
`ExprNode`s are affected by which `BasicBlock`.
- Compute the so-called consesus, i.e., verify that for all the
`ExprNode`s affected by a certain `BasicBlock`, the transformation
would be beneficial in terms of output. Basically:
1) That the number of `!(!=)` transformed into `(==)` outscores the
number of correlated `(!=)` which are transformed into `!(==)`.
2) That the number of `!(==)` transformed into `(!=)` outscores the
number of correlated `(==)` which are transformed into `!(!=)`.
- Actually perform the transformation for those situations where the
consensus agrees.
A bug introduced no loop promotion by mistake, we now correctly exit the
loop promotion routine if the loop has been already promoted to `while`
or `do-while` loop.
This commit does various things oriented at reducing the number of local
variables emitted in C:
- MarkAssignments now know that @Copy and @Assign involving
@LocalVariable only have side effects that affect the local variable
itself; this enables to reduce the number of times we're forced to
emit a local variable due to interfering side effects
- Drop the @AssignmentMarker FunctionTag; AddAssignmentMarkerPass now
doesn't emit @AssignmentMarker anymore; instead it emits groups of
@LocalVariable, @Copy, and @Assign, which benefit from the previous
point
- Drop 2 MarkAssignments::Reasons: HasManyUses and HasUsesOutsideOfBB;
both these have now been aggregated into the AlwaysAssign reason for
simplicity, representing all reasons non involving side effects
- Update BeautifyGHAST and how it reasons about side effects when
beautifying; before this commit it used @AssignmentMarker, now it
looks at @Assign
- Simplify ExitSSA; before this commit it was trying hard to be smart on
where it emitted the store instructions representing the incoming
values of the PHI that was being destroyed; this seemed smart when we
originally did it but it generated C code that was not really better
to read, so this useless complexity is finally gone
The beautification library was split into a separate library for
historical reason, having to do with LLVM passes, their dependencies,
and dirty hacks we had around.
Now the LLVM passes, and the hacks are gone, so we can merge back
everything together.
Pietro Fezzardi