In the new pipeline the root module is split off in its individual
isolated modules at the end of `isolate`. Before splitting, there are a
lot of global variables in the root module and only a small part is
going to be needed after splitting for each module. To avoid excessive
memory usage employ `ConservativeModuleCloner` in `Isolate` so that
only the needed global variables are actually cloned when splitting off.
Re-organize the variants of `libtcg-helpers-*.bc` as such:
* `libtcg-helpers-full-$ARCH.bc`: unchanged, contains all helper
function with their bodies and all CSVs.
* `libtcg-helpers-declarations-only-$ARCH.bc`: all helper
functions have been turned to declarations. All CSVs (except a couple
of special ones) have been dropped.
* `libtcg-helpers-to-inline-$ARCH.bc`: only functions with the
`revng_inline` section retain their body. Only CSVs that are used by
these functions are present.
Lift now loads only the `declarations-only` variant of helpers, as
their body is not required until `inline-helpers`. In `inline-helpers`
the `to-inline` variant is loaded and linked, which then allows the
helpers to be inlined.
Add the `SimplePassManager` and `SimpleFunctionPassManager` classes
which add wrappers around the new LLVM pass manager. Change all the
applicable uses of the legacy pass manager with the wrapper.
Sometimes QEMU will emit code that reads a local temporary *before* it
is assigned in the `TranslationBlock`. This usually happens when lifting
non-code, but it's still a problem since it leads to phis around the
dispatcher, which we don't want.
For example, consider the following x86-64 code:
```
0000000140002000 <.text>:
140002000: f0 lock
140002001: 38 00 cmpb %al, (%rax)
```
It leads to:
```
[libtcg] Translation starting from 0x140002000:Generic64
[libtcg] ---- 0000000040002000
[libtcg] mov_i64 loc2,rax
[libtcg] mov_i64 loc1,rax
[libtcg] mov_i64 cc_src,loc1
[libtcg] mov_i64 loc8,loc0
[libtcg] sub_i64 cc_dst,loc0,loc1
[libtcg] discard cc_src2
[libtcg] discard cc_op
```
Note how `loc0` is read before being initialized.
Currently we zero-initialize all the temporaries. It would be in
princple possible to detect those that need the initialization, which
would also enable us to emit a warning.
Make the interface required by `SingleOutputPipe` similar to other
piperuns by requiring a constructor, the use of `PipeRunArgument`s and
the implementation of a non-static `run` function.
LLVM purges loads from `nullptr` in functions not marked with
`null_pointer_is_valid`. This can lead to uninitialized accesses to tiny
code variables, which in turn lead to cross-`TranslationBlock` phis
which can prevent argumentless outlining.
Adding to the `root` function the `null_pointer_is_valid` attribute
fixes this problem.
This commit drops libptc in favor of its new form libtcg.
It brings several improvements, among which:
* The QEMU version we work on has been upgraded.
* CPUStateAccessAnalysis has been reimplemented in a way that makes it
easier to debug and solves some limitations (e.g., tracking leaking
pointers).
* Identification of pieces of the CPU state that are read by each helper
and fixing access to the CPU state is now performed at build-time.
* We no longer mmap the code we need to translate, dropping all the
issues related to code that needed to be mapped where something is
already present.
* We now have two distinct flavors of helper modules: the full one and
the "slim" one. The latter contains the definition only of functions
we intend to inline. It is used in most of the pipeline, a good thing
since we spend less time optimizing code we don't really care about.
The full module is only used on the re-compilation branch of the
pipeline.
* We no longer split the `cpu_loop` function.
* We change MetaAddress to rely on architectures from `model::` as
opposed to the LLVM ones.
* We no longer attach debug info to LLVM IR containing the original
assembly.
* We now verify that the lifted code only contains code we expect.
* Make the following private headers public:
* Lift/CPUStateAccessAnalysisPass.h
* Lift/CSVOffsets.h
* Lift/PTCDump.h
* Lift/VariableManager.h
* Move from revngSupport to revngLift:
* IRAnnotators.{h,cpp}
* SelfReferencingDbgAnnotationWriter.{h,cpp}
* Move from revngSupport to revngModel:
* FunctionTags.{h,cpp}
* ProgramCounterHandler.{h,cpp}
* Move from revngSupport to revngRecompile:
* OriginalAssemblyAnnotationWriter.{h,cpp}
Before this commit, `forceEmptyMetadata` did not return a bool to notify
when it changed something.
This in turn caused the pass to return the wrong value when the only
change applied was to force the empty metadata.
This commit fixes the issue, letting `forceEmptyMetadata` return a bool,
and propagating that until where it matters.
Alessandro Di Federico