Before this commit, ExitSSAPass was collapsing PHINodes too aggressively
onto the same variable.
In particular we were mishandling the case where two PHINodes were
candidates for being collapsed to the same variable, but they had
overlapping live ranges.
Having overlapping live ranges means that they don't store the same
value (otherwise LLVM would have CSE'd them), so if we collapse them
onto the same variable we end up losing the value.
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
This flag was used with the old C backend to decompile only a single
function from a binary.
The logic of selecting functions in a binary for decompilation is now
part of revng-pipeline, so the -single-decompilation option and the
associated TargetFunctionOption library can be dropped.
Change company name to "rev.ng Labs Srl" in all license headers
to reflect changed company name and legal status
Add missing license headers to files that didn't have one
Pietro Fezzardi