Summary:
Add full instrumentation support (branches, direct and
indirect calls). Add output statistics to show how many hot bytes
were split from cold ones in functions. Add -cold-threshold option
to allow splitting warm code (non-zero count). Add option in
bolt-diff to report missing functions in profile 2.
In instrumentation, fini hooks are fixed to run proper finalization
code after program finishes. Hooks for startup are added to setup
the runtime structures that needs initilization, such as indirect call
hash tables.
Add support for automatically dumping profile data every N seconds by
forking a watcher process during runtime.
(cherry picked from FBD17644396)
Summary:
Change our CMake config for the standalone runtime instrumentation
library to check for the elf.h header before using it, so the build
doesn't break on systems lacking it. Also fix a SmallPtrSet usage where
its elements are not really pointers, but uint64_t, breaking the build
in Apple's Clang.
(cherry picked from FBD17505759)
Summary:
Change our edge profiling technique when using instrumentation
to do not instrument every edge. Instead, build the spanning tree
for the CFG and omit instrumentation for edges in the spanning tree.
Infer the edge count for these edges when writing the profile during
run time. The inference works with a bottom-up traversal of the spanning
tree and establishes the value of the edge connecting to the parent based
on a simple flow equation involving output and input edges, where the
only unknown variable is the parent edge.
This requires some engineering in the runtime lib to support dynamic
allocation for building these graphs at runtime.
(cherry picked from FBD17062773)
Summary:
Avoid directly allocating string and description tables in
binary's static data region, since they are not needed during runtime
except when writing the profile at exit. Change the runtime library to
open the tables on disk and read only when necessary.
(cherry picked from FBD16626030)
Summary:
To allow the development of future instrumentation work, this
patch adds support in BOLT for linking arbitrary libraries into the
binary processed by BOLT. We use orc relocation handling mechanism for
that. With this support, this patch also moves code programatically
generated in X86 assembly language by X86MCPlusBuilder to C code written
in a new library called bolt_rt. Change CMake to support this library as
an external project in the same way as clang does with compiler_rt. This
library is installed in the lib/ folder relative to BOLT root
installation and by default instrumentation will look for the library
at that location to finish processing the binary with instrumentation.
(cherry picked from FBD16572013)
