On 16/04/14 11:17, Joey Ye wrote: >> -----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. >
For thumb code it can get the conditional information it needs from the IT state in the PSR; for ARM code it has to look no further than the instruction itself. R.
