BOLT uses `MCAsmLayout` to calculate the output values of functions and
basic blocks. This means output values are calculated based on a
pre-linking state and any changes to symbol values during linking will
cause incorrect values to be used.
This issue can be triggered by enabling linker relaxation on RISC-V.
Since linker relaxation can remove instructions, symbol values may
change. This causes, among other things, the symbol table created by
BOLT in the output executable to be incorrect.
This patch solves this issue by using `BOLTLinker` to get symbol values
instead of `MCAsmLayout`. This way, output values are calculated based
on a post-linking state. To make sure the linker can update all
necessary symbols, this patch also makes sure all these symbols are not
marked as temporary so that they end-up in the object file's symbol
table.
Note that this patch only deals with symbols of binary functions
(`BinaryFunction::updateOutputValues`). The technique described above
turned out to be too expensive for basic block symbols so those are
handled differently in D155604.
Reviewed By: maksfb
Differential Revision: https://reviews.llvm.org/D154604
BOLT uses MCAsmLayout to calculate the output values of basic blocks.
This means output values are calculated based on a pre-linking state and
any changes to symbol values during linking will cause incorrect values
to be used.
This issue was first addressed in D154604 by adding all basic block
symbols to the symbol table for the linker to resolve them. However, the
runtime overhead of handling this huge symbol table turned out to be
prohibitively large.
This patch solves the issue in a different way. First, a temporary
section containing [input address, output symbol] pairs is emitted to the
intermediary object file. The linker will resolve all these references
so we end up with a section of [input address, output address] pairs.
This section is then parsed and used to:
- Replace BinaryBasicBlock::OffsetTranslationTable
- Replace BinaryFunction::InputOffsetToAddressMap
- Update BinaryBasicBlock::OutputAddressRange
Note that the reason this is more performant than the previous attempt
is that these symbol references do not cause entries to be added to the
symbol table. Instead, section-relative references are used for the
relocations.
Reviewed By: maksfb
Differential Revision: https://reviews.llvm.org/D155604
Use llvm::reverse instead of `for (auto I = rbegin(), E = rend(); I != E; ++I)`
Reviewed By: #bolt, rafauler
Differential Revision: https://reviews.llvm.org/D140516
This has the following advantages:
- std::shared_timed_mutex is macOS 10.12+ only. llvm::sys::RWMutex
automatically switches to a different implementation internally
when targeting older macOS versions.
- bolt only needs std::shared_mutex, not std::shared_timed_mutex.
llvm::sys::RWMutex automatically uses std::shared_mutex internally
where available.
std::shared_mutex and RWMutex have the same API, so no code changes
other than types and includes are needed.
Differential Revision: https://reviews.llvm.org/D138423
A const-qualified reference to function layout allows accessing
non-const qualified basic blocks on a const-qualified function. This
patch adds or removes const-qualifiers where necessary to indicate where
basic blocks are used in a non-const manner.
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D132049
A const-qualified reference to function layout allows accessing
non-const qualified basic blocks on a const-qualified function. This
patch adds or removes const-qualifiers where necessary to indicate where
basic blocks are used in a non-const manner.
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D132049
This adds basic fragment awareness in the exception handling passes and
generates the necessary symbols for fragments.
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D130520
BC::printInstruction(s) has many uses of Function ptr if it's available:
# printing CFI instructions (unconditional)
# printing debug line information (-print-debug-info)
# printing instruction relocations (-print-relocations)
Enable these uses by passing Function ptr from the primary printing entry point:
BinaryBasicBlock::dump.
Reviewed By: maksfb
Differential Revision: https://reviews.llvm.org/D126916
Addresses the warnings emitted by Apple Clang 13.1.6 (Xcode 13.3.1).
Tip @tschuett issue #55404.
Reviewed By: rafauler
Differential Revision: https://reviews.llvm.org/D125733
When a jump table is recovered in postProcessIndirectBranches(),
successors for the containing basic block are added in random order.
Make the order deterministic.
Reviewed By: yota9
Differential Revision: https://reviews.llvm.org/D119672
Summary:
If `addUnknownControlFlow` in `BinaryFunction::postProcessIndirectBranches`
is invoked with a basic block that has multiple edges to the same successor,
it leads to an assertion in `BinaryBasicBlock::removePredecessor`.
For basic blocks with multiple edges to the same successor, the default
behavior of removePredecessor is to remove all occurrences of the
predecessor block in its predecessor list (Multiple=true).
Example:
```A -> B (two edges)
A->removeAllSuccessors()
for each successor of block A: // B twice
// this removes both occurrences of A in B's predecessors list
B->removePredecessor(A);
// this invocation triggers an assert as A is no longer in B's
// predecessor list
B->removePredecessor(A);
```
This issue is not fixed by NormalizeCFG as `removeAllSuccessor` is called
earlier (from `buildCFG` -> `postProcessIndirectBranches`).
Solve this issue by collecting the successors into a set (`SmallPtrSet`) first,
before invoking `SuccessorBB->removePredecessor(this)`.
GitHub issue: https://github.com/facebookincubator/BOLT/issues/187
(cherry picked from FBD30796979)
Summary:
Fix according to Coding Standards doc, section Don't Use
Braces on Simple Single-Statement Bodies of if/else/loop Statements.
This set of changes applies to lib Core only.
(cherry picked from FBD33240028)
Summary:
Switched members of BinaryFunction to ADT where it was possible and
made sense. As a result, the size of BinaryFunction on x86-64 Linux
reduced from 1624 bytes to 1448.
(cherry picked from FBD32981555)
Summary:
Make BOLT build in VisualStudio compiler and run without
crashing on a simple test. Other tests are not running.
(cherry picked from FBD32378736)
Summary:
Moves source files into separate components, and make explicit
component dependency on each other, so LLVM build system knows how to
build BOLT in BUILD_SHARED_LIBS=ON.
Please use the -c merge.renamelimit=230 git option when rebasing your
work on top of this change.
To achieve this, we create a new library to hold core IR files (most
classes beginning with Binary in their names), a new library to hold
Utils, some command line options shared across both RewriteInstance
and core IR files, a new library called Rewrite to hold most classes
concerned with running top-level functions coordinating the binary
rewriting process, and a new library called Profile to hold classes
dealing with profile reading and writing.
To remove the dependency from BinaryContext into X86-specific classes,
we do some refactoring on the BinaryContext constructor to receive a
reference to the specific backend directly from RewriteInstance. Then,
the dependency on X86 or AArch64-specific classes is transfered to the
Rewrite library. We can't have the Core library depend on targets
because targets depend on Core (which would create a cycle).
Files implementing the entry point of a tool are transferred to the
tools/ folder. All header files are transferred to the include/
folder. The src/ folder was renamed to lib/.
(cherry picked from FBD32746834)
