llvm dev - Jun 2009 - [LLVMdev] unwind/invoke design

On Mon, Jun 15, 2009 at 7:08 PM, Aaron
Gray<aaronngray.lists at googlemail.com> wrote:
>> The documentation of unwind/invoke is quite clear and does exactly
>> what I need: unwinding the stack. I don't need it to carry an
object
>> back. I don't need it to figure out what the type of the object is
or
>> what catch() blocks it matches. I just need it to unwind the stack.
>> The rest is my job as a part of the runtime. Unfortunately, I have
>> learned that while this works with the bytecode evaluator, it
doesn't
>> work with the JIT or native codegen [1].
>
> DWARF EH maybe what you want, it has zero overhead on normal calls and I
> believe it is built into LLVM's assemblers. A DWARF style EH is also
built
> into the JIT too.
How do I tell llc to output dwarf-style 'unwnd' ? Both -enable-eh and
-enable-correct-eh-support compile 'unwind' to nothing on x86 with llc
v2.5.

On 2009-06-15 20:26, Wesley W. Terpstra wrote:
> On Mon, Jun 15, 2009 at 7:08 PM, Aaron
> Gray<aaronngray.lists at googlemail.com> wrote:
>   
>>> The documentation of unwind/invoke is quite clear and does exactly
>>> what I need: unwinding the stack. I don't need it to carry an
object
>>> back. I don't need it to figure out what the type of the object
is or
>>> what catch() blocks it matches. I just need it to unwind the stack.
>>> The rest is my job as a part of the runtime. Unfortunately, I have
>>> learned that while this works with the bytecode evaluator, it
doesn't
>>> work with the JIT or native codegen [1].
>>>       
>> DWARF EH maybe what you want, it has zero overhead on normal calls and
I
>> believe it is built into LLVM's assemblers. A DWARF style EH is
also built
>> into the JIT too.
>>     
>
> How do I tell llc to output dwarf-style 'unwnd' ? Both -enable-eh
and
> -enable-correct-eh-support compile 'unwind' to nothing on x86 with
llc
> v2.5.
>   
Write some C++ code into llvm.org/demo, and watch the output assembly,
for example:
int foo() {
 throw 1;
}

int bar() {
try {
  foo();
} catch (...) {
}
}

That should show the basics of exception handling.

Best regards,
--Edwin

2009/6/15 Török Edwin <edwintorok at gmail.com>:
> Write some C++ code into llvm.org/demo, and watch the output assembly,
That shows how to use the c++ runtime for handling c++ style
exceptions. More useful might be an llvm implementation of
__cxa_throw, which I could then modify. ;)