A new hidden option -print-on-crash that prints the IR as it was upon entering
the last pass when there is a crash.
The IR is saved in its print form before each pass is started and a
signal handler is registered. If the compilation crashes, the signal
handler will print the saved IR to dbgs(). This option
can be modified using -print-module-scope to get the IR for the complete
module. Note that this option only works with the new pass manager.
Although it is not included in the patch, this was tested by adding a hidden
option to a pass that caused the pass to call __builtin_trap().