The `FunctionCallIdentification` analysis now provides a custom view on
the CFG where 1) dispatcher-related basic blocks are absent, 2) nodes
performing functions calls have an edge to their return address and 3)
nodes ending with a return instruction have no successor.
This CFG is now employed by the reaching definitions analysis and OSRA.
Additionally, the implementation of the `visitSuccessors` and
`visitPredecessors` method has been reviewed. It now consists in a class
that needs to be inherited and for which two methods should be
implemented, one to perform the visit of a block and another one to
enumerate the successors.
In addition, all the users of `visitSuccessors`/`visitPredecessors` have
been updated, a simple set of tests has been introduced and
`GeneratedCodeBasicInfo::visitPredecessors` has been dropped.
This commit fixes a problem that led to use SET to discover very very
simple jump targets: the return addresses of functions call.
Since in this situation, for each call, we needed to run SET, this
commit leads to a *huge* improvements in terms of translation
performance.
This commit also enforces renaming of the translated basic blocks after
they get split and update the ground truth for several analysis tests.
The Reaching Definitions Analysis used to ignore all the memory access
that were not relative to a CSV or an `alloca`. In certain situations,
in particular in x86 which makes heavy use of the stack, this led to
miss certain links that were vital for a correct identification of
certain jump targets.
As an example consider the following example:
cmp DWORD PTR [rbx+0x8],0x5
ja 4bc5c8 <uw_update_context_1+0x148>
mov eax,DWORD PTR [rbx+0x8]
movsxd rax,DWORD PTR [r12+rax*4]
add rax,r12
jmp rax
The constaint on `rbx+0x8` is not propagated to the use after the jump,
due to a missing link.
This commit fixes this by tracking all the memory accesses within the
expressive power of the `MemoryAccess` class, in particular those
expressed as register plus offset.
Additionally, this commit also makes RDA consider as reaching
definitions for a `load` only those definitions that match exactly the
load address, while previously we were considering all the `mayAlias`
definitions. This situation, in combination with the previous change,
led to have paths with multiple reaching definitions, which was
problematic for the path sensitive merge.
Finally, we consider a definition to be clobbered only if there's an
exact store to the esame address, instead of a store on an aliasing
address.
In function isolation, every time we met a jump to an unexpected basic
block (i.e., a basic block that is not part of the current function), we
used to throw an exception. However this is unnecessary since oftentimes
it is sufficient to call the `function_dispatcher` or even perform a
regular function call.
The most obvious example is the case of a direct tail call. In this
situation performing a function call to the corresponding isolated
function is the most appopriate thing to do.
`getType` didn't have a `BlockType` to represent the entry basic block
of the `root` function. Therefore, such basic block was erroneously
identified as a translated basic block.
This commit uses SET, information about canonical values and labels to
detect if an indirect function call is targeting an external symbol.
The strings used for the name of external symbols are uniqued global
variables. This commit also uses this approach for the disassembly of
original instructions, which used to be metadata.
So far we've been tracking only base-relative relocations in an ad-hoc
fashion. This commit introduces a data structure that can describe the
most common relocations, including those for `.got`, `.got.plt`,
base-relative and `R_*_COPY`.
A label describes a range of the binary. A label can be generated from a
symbol (basically assigning a name to range of the binary) or from a
relocation, describing the content of a certain range.
This commit generates labels from symbols and relocations, including
MIPS implicit relocations.
This commit also introduces canonical values.
A register can have a canonical value, i.e., a value that register will
assume when the analyzed module is being run. This is typically useful
for the value of the global pointer, which is different from one module
to another but, within a module, is stable.
This commit registers the canonical value of `gp` (in MIPS), if
available.
Updating to LLVM 7 mainly involved the following steps:
* Upgrade APIs for folding ConstantExpr.
* Upgrade APIs for GraphTraits.
* Upgrade APIs for DominatorTreeBase.
* Upgrade APIs for BinaryFormat to parse ELFs.
* Fix the LLVM Linker to properly link the QEMU helpers.
* Disable the new optnone attribute even with optimization -O0. This is
necessary to allow SROA to do its job properly.
* Upgrade APIs to delete Instructions.
* Properly cleaning up orphaned metadata still referring to Instructions
that have been destroyed. Recent versions of LLVM are more strict in
this respect, and will assert when compiled in debug.
* Avoid using LLVM `getGlobalContext` which has been removed from newer
versions of LLVM.
* Upgrade tests to use the new APIs.
* Upgrade APIs for instruction iterators and reverse iterators.
This commit reimplements the (conditional) reaching definitions passes
as an instance of a monotone framework.
The `ConditionNumberingPass` has also been reworked in the way it
exposes its results, but it's otherwise unchanged.
A proper unit testing framework is also available to ensure everything
works as supposed to.
In a `MonotoneFramework` it is sometimes necessary to change the
information propagated on a branch w.r.t. another branch.
This commit introduces the `handleEdge` function that allows
`MonotoneFramework` implementors to modify the `LatticeElement` produced
by `transfer`.
This commit dismisses the `argparse` library (the only non-runtime C
component of rev.ng) in favor of LLVM's CommandLine library, which
offers several benefits. Among others, now command line arguments can be
easily specified as a global variable, decentralizing their management
and avoiding the long list of arguments in the constructor of singleton
objects such as `CodeGenerator`.
This commit introduces `revng_log`, a macro analagous to `revng_assert`,
which basically allows to have the benefit of the `Logger` class without
having to compute the expression to log if the logger is disabled.
This commit also completely dismisses the `DBG` macro, converting all
the old code to `Logger` + `revng_log`.
This commit moves around most files. The new directory structure is as
follows:
* `lib/$LIBRARY/`: contains a library, i.e., a set of `.cpp` files used
by multiple libraries/tools.
* `include/revng/$LIBRARY/`: contains the public headers associated to
the library in `lib/$LIBRARY/`.
* `tools/$TOOL/`: directory where all the `.cpp` files (and private
headers) for a tool reside. Currently we have two tools: `revamb` and
`revamb-dump`.
On top of this, all file names are now in camel case.
`FunctionPass` has a static field `ID`. In templated passes, this needs
to be declared in the header file and defined in a `.cpp` file.
This does this, the right way.
This commit enforces on the whole project the usage of our own assertion
system. This means all calls to `abort`, `assert` and `llvm_unreachable`
have been replaced with calls to `revng_abort`, `revng_assert` and
`revng_unreachable`, respectively.
The error messages, usually expressed as `assert(Condition &&
"Message")` have now been replaced using the second (optional) argument
of `revng_assert`.
Additionally, all the `assert(false)` statements have been replaced with
calls to `revng_abort`. Apart from readibility, this ensures the
compilers is aware of the fact that call will never return.
This change will enable us to drop many statements whose sole purpose
was marking a variable employed in an assertion as used in release
mode. In fact, with the new assertion system this is no longer
necessary.
We used to have a `_` prefix for include guards macros, however,
according to the standard, macros starting with an underscore are
reserved. This commit drops them all.
This is a very large commit importing the reviewed (and heavily
simplified) stack analysis and the new ABI analysis, which provides
information on the calling convention of each function and so on.
For an overview of the new analyses please consult OVERVIEW.md.
Alessandro Di Federico