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This new JIT event listener supports generating profiling data for the linux 'perf' profiling tool, allowing it to generate function and instruction level profiles. Currently this functionality is not enabled by default, but must be enabled with LLVM_USE_PERF=yes. Given that the listener has no dependencies, it might be sensible to enable by default once the initial issues have been shaken out. I followed existing precedent in registering the listener by default in lli. Should there be a decision to enable this by default on linux, that should probably be changed. Please note that until https://reviews.llvm.org/D47343 is resolved, using this functionality with mcjit rather than orcjit will not reliably work. Disregarding the previous comment, here's an example: $ cat /tmp/expensive_loop.c bool stupid_isprime(uint64_t num) { if (num == 2) return true; if (num < 1 || num % 2 == 0) return false; for(uint64_t i = 3; i < num / 2; i+= 2) { if (num % i == 0) return false; } return true; } int main(int argc, char **argv) { int numprimes = 0; for (uint64_t num = argc; num < 100000; num++) { if (stupid_isprime(num)) numprimes++; } return numprimes; } $ clang -ggdb -S -c -emit-llvm /tmp/expensive_loop.c -o /tmp/expensive_loop.ll $ perf record -o perf.data -g -k 1 ./bin/lli -jit-kind=mcjit /tmp/expensive_loop.ll 1 $ perf inject --jit -i perf.data -o perf.jit.data $ perf report -i perf.jit.data - 92.59% lli jitted-5881-2.so [.] stupid_isprime stupid_isprime main llvm::MCJIT::runFunction llvm::ExecutionEngine::runFunctionAsMain main __libc_start_main 0x4bf6258d4c544155 + 0.85% lli ld-2.27.so [.] do_lookup_x And line-level annotations also work: │ for(uint64_t i = 3; i < num / 2; i+= 2) { │1 30: movq $0x3,-0x18(%rbp) 0.03 │1 38: mov -0x18(%rbp),%rax 0.03 │ mov -0x10(%rbp),%rcx │ shr $0x1,%rcx 3.63 │ ┌──cmp %rcx,%rax │ ├──jae 6f │ │ if (num % i == 0) 0.03 │ │ mov -0x10(%rbp),%rax │ │ xor %edx,%edx 89.00 │ │ divq -0x18(%rbp) │ │ cmp $0x0,%rdx 0.22 │ │↓ jne 5f │ │ return false; │ │ movb $0x0,-0x1(%rbp) │ │↓ jmp 73 │ │ } 3.22 │1 5f:│↓ jmp 61 │ │ for(uint64_t i = 3; i < num / 2; i+= 2) { Subscribers: mgorny, llvm-commits Differential Revision: https://reviews.llvm.org/D44892 llvm-svn: 337789
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