Summary:
The regular perf2bolt aggregation job is to read perf output directly.
However, if the data is coming from a database instead of perf, one
could write a query to produce a pre-aggregated file. This function
deals with this case.
The pre-aggregated file contains aggregated LBR data, but without binary
knowledge. BOLT will parse it and, using information from the
disassembled binary, augment it with fall-through edge frequency
information. After this step is finished, this data can be either
written to disk to be consumed by BOLT later, or can be used by BOLT
immediately if kept in memory.
File format syntax:
{B|F|f} [<start_id>:]<start_offset> [<end_id>:]<end_offset> <count>
[<mispred_count>]
B - indicates an aggregated branch
F - an aggregated fall-through (trace)
f - an aggregated fall-through with external origin - used to disambiguate
between a return hitting a basic block head and a regular internal
jump to the block
<start_id> - build id of the object containing the start address. We can
skip it for the main binary and use "X" for an unknown object. This will
save some space and facilitate human parsing.
<start_offset> - hex offset from the object base load address (0 for the
main executable unless it's PIE) to the start address.
<end_id>, <end_offset> - same for the end address.
<count> - total aggregated count of the branch or a fall-through.
<mispred_count> - the number of times the branch was mispredicted.
Omitted for fall-throughs.
Example
F 41be50 41be50 3
F 41be90 41be90 4
f 41be90 41be90 7
B 4b1942 39b57f0 3 0
B 4b196f 4b19e0 2 0
Reviewed By: maksfb
Differential Revision: D8887182
fbshipit-source-id: d8ea85dbf0a
Summary:
When a given function B, located after function A, references
one of A's basic blocks, it registers a new global symbol at the
reference address and update A's Labels vector via
BinaryFunction::addEntryPoint(). However, we don't update A's branch
targets at this point. So we end up with an inconsistent CFG, where the
basic block names are global symbols, but the internal branch operands
are still referencing the old local name of the corresponding blocks
that got promoted to an entry point. This patch fix this by detecting
this situation in addEntryPoint and iterating over all instructions,
looking for references to the old symbol and replacing them to use the
new global symbol (since this is now an entry point).
Fixes#26
Reviewed By: maksfb
Differential Revision: D8728407
fbshipit-source-id: da7cde1
Summary:
While removing unreachable blocks, we may decide to remove a
block that is listed as a target in a jump table entry. If we do that,
this label will be then undefined and LLVM assembler will crash.
Mitigate this for now by not removing such blocks, as we don't support
removing unnecessary jump tables yet.
Fixes#20
Reviewed By: maksfb
Differential Revision: D8730269
fbshipit-source-id: b12d104
Summary:
Create folders and setup to make LIT run BOLT-only tests. Add
a test example. This will add a new make/ninja rule "check-bolt" that
the user can invoke to run LIT on this folder.
Reviewed By: maksfb
Differential Revision: D8595786
fbshipit-source-id: b13d2e5
