[patch] Disable if_conversion2 for Og

[Joey Ye]

> -----Original Message-----
> From: Richard Earnshaw
> Sent: Wednesday, April 16, 2014 6:04 PM
> To: Joey Ye
> Cc: gcc-patches@gcc.gnu.org
> Subject: Re: [patch] Disable if_conversion2 for Og
> 
> On 16/04/14 11:02, Joey Ye wrote:
> >
> >
> >> -----Original Message-----
> >> From: Richard Earnshaw
> >> Sent: Wednesday, April 16, 2014 5:44 PM
> >> To: Joey Ye
> >> Cc: gcc-patches@gcc.gnu.org
> >> Subject: Re: [patch] Disable if_conversion2 for Og
> >>
> >> Arguably, this is a bug in gdb.  The debugger should understand when
> >> a breakpointed conditional instruction is not going to execute and
> >> silently continue.  That preserves the illusion of not executing the
> >> code without requiring the compiler to de-optimize things.
> >>
> >> R.
> > Or compiler just optimizes it, and emits generic DWARFx information to
> > help GDB handle it in more target independently?
> >
> > - Joey
> >
> 
> I'm not sure extra dwarf info would help much.  The debugger still has to
> understand that the breakpoint has not really been hit.
> 
> R.
Yes, it is inevitable. But without extra dwarf info it will be even more
painful: each time setting break-point or break-point hits it has to decode
the break-pointed instructions and its context to search for conditional
execution and IT blocks.

- Joey