This is the mail archive of the
gdb@sourceware.org
mailing list for the GDB project.
debug_frame for optimized code
- From: Christophe LYON <christophe dot lyon at st dot com>
- To: gdb at sources dot redhat dot com
- Date: Wed, 19 Oct 2005 13:42:38 +0200
- Subject: debug_frame for optimized code
Hi all,
I know this is not a question directly related to GDB, but I don't know
where else I could ask....
I am currently working on the debug_frame info emission in our C/C++
compiler (based on Open64).
I have recently come across optimized code which I don't know how to handle.
Consider the following function:
foo() {
PROLOGUE
if (COND1) {
SAVE_REG r1 to stack
compute
bar1()
RESTORE r1
}
else if (COND2) {
bar2()
}
EPILOGUE
}
Suppose that the generated code looks like:
foo:
PROLOGUE
COND1
if true goto LABEL1
COND2
if true goto LABEL2
epilogue_label:
EPILOGUE
LABEL1:
SAVE register r1 to stack
compute....
goto CALL_BAR1
LABEL2:
CALL bar2
goto epilogue_label
CALL_BAR1:
CALL bar1
RESTORE r1
goto epilogue_label
So my question is:
what debug_frame info should I generate around LABEL1, LABEL2, and
CALL_BAR1 ?
Should I repeat all the info of the prologue before LABEL1 and LABEL2?
for CALL_BAR1, should I also add the save of register r1 ?
It's also unclear to me if I can/should use the
remember_state/restore_state dwarf operators.
Indeed, what is the rule?
Use remember_state after the prologue, and use restore state at LABEL1
and LABEL2?
But as states are defined as a stack, it means I would restore twice the
same thing...
Any help/suggestion highly appreciated!
Thanks,
Christophe.