This utility revives the debug-ir pass in LLVM, but as a standalone tool. I found the idea of having a separate utility simpler after knowing that this earlier patch to revive it as a pass inside LLVM didn't go through.
Let us assume that the LLVM-IR to be debugged is named hello.ll.
Such a file can be dynamically generated, or using clang as
clang -emit-llvm -o hello.ll -S hello.c.hello.c
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
if (!strcmp(argv[0], "hello")) {
printf("Hello World\n");
} else {
printf("No hello\n");
}
return 0;
} This tool requires LLVM-17 to be installed.
git clone https://github.com/vaivaswatha/debugir.git debugir
cd debugir; mkdir build; cd build
cmake -DCMAKE_BUILD_TYPE=Release ../
cmake --build .If you have LLVM installed in a non-standard path, you may provide the
additional CMake argument -DLLVM_DIR=/path/to/llvm.
You should now have an executable file debugir in the build directory.
./debugir hello.llThis produces a file hello.dbg.ll. NOTE The utility also overwrites
the input LLVM-IR file (if you have comments in it, they will be lost).
The new file hello.dbg.ll is semantically the same as the input file,
but with debug information referring to the input file.
If you now debug hello.dbg.ll (instead of debugging hello.ll), the
debugger can pickup and display hello.ll as the execution proceeds.
Note: LLVM values that don't have an explicit name cannot have their
names (and hence values) seen in GDB. To workaround this, provide
explicit names yourself or run the instruction namer pass by providing
the -instnamer flag to debugir.
Following on the example here
let us try and debug hello.dbg.ll.
gdb --args lli -jit-kind=mcjit hello.dbg.ll
(gdb) break hello.ll:25 # set breakpoint at line 25 in hello.ll
(gdb) run lldb lli -- -jit-kind=mcjit hello.dbg.ll
(lldb) break set -y hello.ll:25 # set breakpoint at line 25 in hello.ll
(lldb) runYou should now hit the program at line 25 in hello.ll, assuming that
line 25 is a valid line number in the LLVM source. Change this line number
to an appropriate value or to a function name. Note: Since lli, at the
time of invocation from gdb will not have, yet, loaded the object file for
hello, you will need to set set breakpoint pending on in gdb.
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