Before this commit, the code was making a couple of broken assumptions on
OpaqueExtractValues
- that OpaqueExtractValues were always ordered in the same way as struct
fields (e.g. the OpaqueExtractValue extracting field 0 was always the
first use of the struct-typed value it was extracting from)
- that there was always one and exactly one OpaqueExtractValue for each
field index in the struct
This commit fixes the issue, while reusing available facilities for
dealing with OpaqueExtractValues.
This commit heavily reworks how we handle returned values, making things
a bit more elegant.
Apart from this, it fixes how were handling types that on the model are
aggregates but were being returned via registers on the IR.
This commit:
1. Introduces an alloca for stack arguments of a function. This enables
us to "write" to stack argument. In order to do so, we simply map the
relevant stack portion to the alloca that, since it's a memory
object, can be `load`'d from and `store`'d to.
Note that `llvm::Argument`s are always scalar since if the original
argument was an aggregate, it would have been passed as a pointer,
which is a scalar.
Note also that previously we were using scalar arguments as if they
were *pointers* to the stack arguments. This commit fixes that too
(and updates the tests accordingly).
2. Introduces an alloca for *scalar* stack arguments of a call site.
The alloca is then mapped to the corresponding part of the stack.
Previously, there was no redirection and negative offsets from
`_stack_frame` would pop up.
This commit splits in two stages handleCallSite and
handleMemoryAccess. Running the latter after all the call sites have
been handled, is necessary in order to properly replace certain memory
accesses targeting stack arguments of a call site.
This commit:
* Introduces `_` as a prefix for all non-user entities we emit in
decompiled code.
Also, some names have been changed to be more concise.
Specifically, the following entities have changed:
`_ENUM_UNDERLYING`, `_ABI`, `_REG`, `_padding_at_`,
`_artificial_struct_`, `_artificial_wrapper_`, `_stack`,
`_break_from_loop_`, `_var_`, `_stack_arguments`,
`_artificial_struct_returned_`, `_enum_max_value_`.
* Introduce _PACKED for `__attribute__((packed))`.
* `EnumEntry` name: drop the `EnumType` name prefix.
Before this commit, we were only copying the metadata attached to the
CallInst, but we need to copy also the attributes, otherwise we might
lose important information, such as `nomerge`.
We were not properly handling functions with a `CABIFunctionType` whose
return value covered multiple registers (e.g., a `uint64_t` being
returned through two registers in i386).
Also, we were not correctly handling `CABIFunctionType` returning a
integer type that is smaller than the register containing it (e.g., a
`uint32_t` being returned through `rax` in x86-64).
This commit fixes both situations.
If a function was returning a scalar, we used to forward the return type
from before Segregate. However, this was not OK in case a return value
was in a 64-bit register, but was actually using only the lower 32-bits.
This commit improves handling of such situation.
This commit enables to emit accesses with the square bracket array
access operator on pointers.
This is accomplished by adding an additional mandatory argument to
ModelGEP (AND NOT to ModelGEPRef) to represent this case.
MakeModelGEPPass is updated to take this into account, together with all
the other passes that handle ModelGEPs.
In SegregateStackAccesses sometimes we have to replace a call whose call
type does not match the callee type. Specifically when the return type
is a `StructType`, sometimes the call returns an identical `StructType`,
but with a different identity.
This commit adapts the return type of new calls on the fly.
SegregateStackAccesses creates new functions. Iterating over existing
functions while creating new ones is problematic, so we now first
collect all the functions we want to inspect and then process them.
SegregateStackAccesses and PromoteStackPointer were not handling
functions declarated (but not defined) properly.
This commit fixes this, in part by adopting `TaggedFunctionPass`.
Alessandro Di Federico