Before this commit, MakeModelCastPass was assuming that it would never
try to emit casts involving non-scalars, which don't compile in C.
From now on, the semantic of ModelCast in understood to be bitcast, and
it's valid also when involving non-scalar types.
This may cause the emission of ModelCast that are then emitted in C as
casts that don't compile.
Since the LLVM-based decompilation pipeline is deprecated in favor of
the clift-based decompilation pipeline, this is now considered
acceptable, as long as the C backend prints a warning and a comment on
the broken cast.
This commits reworks MakeModelCastPass so that the computation the of
arguments for the invocation of a ModelCast are now computed later: not
when we decided that a cast must be emitted, but right before we emit
the call.
This simplifies the code and lays the groundwork for relaxing some
assertions later.
This commit adds support in RemoveLoadStore for load/store instructions
such that the pointee of their pointer operand on LLVM is does not match
the pointee type on the Model (i.e. not areMemOpCompatible).
These cases are handled by emitting a Copy/Assign whose address operand
is a ModelGEP with a type matching the LLVM pointee, so that when these
are emitted as expressions in C the dereference operation is guaranteed
to access memory at a size that is compatible with LLVM, which represent
the semantic of what happens in the binary.
Before this commit, SwitchToStatement, in Legacy mode, was evaluating
the injection of Copy instruction an all uses at the same time, while
it's perfectly feasible, depending on how the surrounding IR is shaped,
that calls to Copy are only necessary on some of the uses.
This commit fixes, that evaluating the emission of a call to Copy on
each Use separately.
The previous conversion from LLVM to MLIR was translating plain LLVM IR
to LLVM MLIR Dialect, as a preliminary step for further conversion from
LLVM MLIR Dialect to Clift.
This is not how things are expected to work anymore, so the old code is
now dead and can be removed.
This commit changes the prototype of getCopeType, so that it now takes 2
arguments.
1. The llvm::Type returned by the Copy function. This can be any scalar
llvm::Type.
2. The llvm::type of the argument representing the reference to the
value being copied. This should be a pointer-sized integer, where
pointer-sized means with the same size of a pointer in the
architecture in the input binary.
The second argument is not strictly necessary for now, because the whole
decompilation framework expects a binary with a single architecture,
hence a well defined unambiguous pointer size.
This will be used fully only when we start supporting multiple binaries.
Whenever that happens, if we haven't already fully dropped the Copy
helper function we will have to update the associated
OpaqueFunctionsPool to a type pair as key: the return type and the type
of the argument.
Ivan Krysak