| Issue |
55528
|
| Summary |
[ORC] Perf profiling integration not working in lli
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
tetzank
|
The `perf` profiling integration in `lli` does not work with the ORC jit engine. There are no JitDump files created in ~/.debug/jit/. Hence, `perf report` does not know function addresses and boundaries of jitted code.
The following steps work for MCJIT (--jit-kind=mcjit), but not ORC. LLVM needs to be build with perf support: LLVM_USE_PERF=ON.
Simple C program *pi.c* to test profiling:
```C
#include <stdlib.h>
#include <stdio.h>
static double pi(size_t n){
double res = 4.0;
for(size_t i=0,v=3; i<n; ++i,v+=4){
res -= 4.0 / (v);
res += 4.0 / (v+2);
}
return res;
}
int main(int argc, char *argv[]){
if(argc != 2){
puts("requires n as input");
return -1;
}
size_t n = atoi(argv[1]);
double p = pi(n);
printf("%lu: %f\n", n, p);
return 0;
}
```
Convert to LLVM IR:
`$ clang -S -emit-llvm pi.c -o pi.ll`
Profile execution:
```
$ perf record -k 1 lli --jit-kind=mcjit pi.ll 100000000
$ perf inject -j -i perf.data -o perf.data.jitted
$ perf report -i perf.data.jitted
```
Without `--jit-kind=mcjit`, ORC is used by default which does not produce dump files. Therefore, `perf report` does not know about the jitted code.
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