3bece3d72d
Currently llvm-exegesis assumes that there will only be 3 symbols in the snippet object, in which the benchmarking function 'foo' is always the last symbol. These assumptions do not hold for object file formats of other targets we support downstream. I think it would be more ideal to generalize this part of the logics into a simple search on all symbols, as proposed by this patch.
llvm-exegesis
llvm-exegesis is a benchmarking tool that accepts or assembles a snippet and
can measure characteristics of that snippet by executing it while keeping track
of performance counters.
Currently Supported Platforms
llvm-exegesis is quite platform-dependent and currently only supports a couple
platform configurations for benchmarking. The limitations are listed below.
Analysis mode in llvm-exegesis is supported on all platforms on which LLVM is.
Currently Supported Operating Systems for Benchmarking
Currently, llvm-exegesis only supports benchmarking on Linux. This is mainly
due to a dependency on the Linux perf subsystem for reading performance
counters.
The subprocess execution mode and memory annotations currently only supports Linux due to a heavy reliance on many Linux specific syscalls/syscall implementations.
Currently Supported Architectures for Benchmarking
Currently, using llvm-exegesis for benchmarking is supported on the following
architectures:
- x86
- 64-bit only due to this being the only implemented calling convention
in
llvm-exegesiscurrently.
- 64-bit only due to this being the only implemented calling convention
in
- ARM
- AArch64 only
- MIPS
- PowerPC (PowerPC64LE only)
Note that not benchmarking functionality is guaranteed to work on all platforms.
Memory annotations are currently only supported on 64-bit X86. There is no
inherent limitations for porting memory annotations to other architectures, but
parts of the test harness are implemented as MCJITed assembly that is generated
in ./lib/X86/Target.cpp that would need to be implemented on other architectures
to bring up support.