Summary:
The CFG represents "the ultimate source of truth". Transformations
on functions and blocks have to update the CFG and fixBranches() would
make sure the correct branch instructions are inserted at the end of
basic blocks (or removed when necessary).
We do require a conditional branch at the end of the basic block if
the block has 2 successors as CFG currently lacks the conditional
code support (it will probably stay that way). We only use this
branch instruction for its conditional code, the destination is
determined by CFG - first successor representing true/taken branch,
while the second successor - false/fall-through branch.
When we reverse the branch condition, the CFG is updated accordingly.
The previous version used to insert jumps after some terminating
instructions sometimes resulting in a larger code than needed. As a
result with the new version 1 extra function becomes overwritten for
HHVM binary.
With this diff we also convert conditional branches with one successor
(result of code from __builtin_unreachable()) into unconditional
jumps.
(cherry picked from FBD3802062)
Summary:
I've added a verbosity level to help keep the BOLT spewage to a minimum.
The default level is pretty terse now, level 1 is closer to the original,
I've saved level 2 for the noisiest of messages. Error messages should
never be suppressed by the verbosity level only warnings and info messages.
The rational behind stream usage is as follows:
outs() for info and debugging controlled by command line flags.
errs() for errors and warnings.
dbgs() for output within DEBUG().
With the exception of a few of the level 2 messages I don't have any strong feelings about the others.
(cherry picked from FBD3814259)
Summary:
Added an ICF pass to BOLT, that can recognize identical functions
and replace references to these functions with references to just one
representative.
(cherry picked from FBD3460297)
Summary:
I've factored out the instruction printing and size computation routines to
methods on BinaryContext. I've also added some more debug print functions.
This was split off the ICP diff to simplify it a bit.
(cherry picked from FBD3610690)
Summary: The inference algorithm for counts of fall through edges takes possible jumps to landing pad blocks into account. Also, the landing pad block execution counts are updated using profile data.
(cherry picked from FBD3350727)
Summary:
A simple optimization to prevent branch misprediction for tail calls.
Convert the sequence:
j<cc> L1
...
L1: jmp foo # tail call
into:
j<cc> foo
but only if 'j<cc> foo' turns out to be a forward branch.
(cherry picked from FBD3234207)
Summary:
Updates DWARF lexical blocks address ranges in the output binary after optimizations.
This is similar to updating function address ranges except that the ranges representation needs
to be more general, since address ranges can begin or end in the middle of a basic block.
The following changes were made:
- Added a data structure for iterating over the basic blocks that intersect an address range: BasicBlockTable.h
- Added some more bookkeeping in BinaryBasicBlock. Basically, I needed to keep track of the block's size in the input binary as well as its address in the output binary. This information is mostly set by BinaryFunction after disassembly.
- Added a representation for address ranges relative to basic blocks (BasicBlockOffsetRanges.h). Will also serve for location lists.
- Added a representation for Lexical Blocks (LexicalBlock.h)
- Small refactorings in DebugArangesWriter:
-- Renamed to DebugRangesSectionsWriter since it also writes .debug_ranges
-- Refactored it not to depend on BinaryFunction but instead on anything that can be assined an aoffset in .debug_ranges (added an interface for that)
- Iterate over the DIE tree during initialization to find lexical blocks in .debug_info (BinaryContext.cpp)
- Added patches to .debug_abbrev and .debug_info in RewriteInstance to update lexical blocks attributes (in fact, this part is very similar to what was done to function address ranges and I just refactored/reused that code)
- Added small test case (lexical_blocks_address_ranges_debug.test)
(cherry picked from FBD3113181)
Summary:
Changes DataReader to organize branch perf data per function name and
sets up logistics to bring this data to BinaryFunction::buildCFG(). To do this,
we expand BinaryContext with a const reference to DataReader. This patch also
adds the "-dump-functions" flag to force llvm-flo to dump the current state of
BinaryFunctions once they are disassembled and their CFG built, allowing us to
test whether the builder is sane with LLVM LIT tests.
(cherry picked from FBD2534675)
