[PATCH][Version 3]Come up with -flive-patching master option.

[Qing Zhao]

the patch has been committed today as:

https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=266627 <https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=266627>

I will try to update the gcc9 change page soon.

thanks.

Qing

> On Nov 28, 2018, at 2:24 PM, Qing Zhao <qing.zhao@oracle.com> wrote:
> 
>> 
>> On Nov 28, 2018, at 9:52 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
>> 
>>> 
>>> 2018-11-20  qing zhao  <qing.zhao@oracle.com>
>>> 
>>> 	* cif-code.def (EXTERN_LIVE_ONLY_STATIC): New CIF code.
>>> 	* common.opt: Add -flive-patching flag.
>>> 	* doc/invoke.texi: Document -flive-patching.
>>> 	* flag-types.h (enum live_patching_level): New enum.
>>> 	* ipa-inline.c (can_inline_edge_p): Disable external functions from
>>> 	inlining when flag_live_patching is LIVE_PATCHING_INLINE_ONLY_STATIC.
>>> 	* opts.c (control_options_for_live_patching): New function.
>>> 	(finish_options): Make flag_live_patching incompatible with flag_lto.
>>> 	Control IPA optimizations based on different levels of 
>>> 	flag_live_patching.
>>> 
>>> gcc/testsuite/ChangeLog:
>>> 
>>> 2018-11-20  qing zhao  <qing.zhao@oracle.com>
>>> 
>>> 	* gcc.dg/live-patching-1.c: New test.
>>> 	* gcc.dg/live-patching-2.c: New test.
>>> 	* gcc.dg/live-patching-3.c: New test.
>>> 	* gcc.dg/tree-ssa/writeonly-3.c: New test.
>>> 	* gcc.target/i386/ipa-stack-alignment-2.c: New test.
>>> 
>> 
>> I am still somewhat worried about possible use with C++ programs where
>> we will kill all inlining of comdats, but I guess we could discuss that
>> when it becomes an issue.
> 
> Okay. If this will be a problem later when we use live-patching in more C++ applications, let’s 
> revisit it at that time. 
> 
>> +
>> +      /* FIXME: disable unreachable code removal.  */
>> 
>> Disabling unreachable code removal will really introduce a lot of extra
>> dead code, can't live patches just provide what they need if the code
>> was earlier removed.
>> +
>> +      /* discovery of functions/variables with no address taken.  */
>> +      if (opts_set->x_flag_ipa_reference_addressable
>> +	  && opts->x_flag_ipa_reference_addressable)
>> +	error_at (loc,
>> +		  "%<-fipa-reference-addressable%> is incompatible with "
>> +		  "%<-flive-patching=inline-only-static|inline-clone%>");
>> +      else
>> +	opts->x_flag_ipa_reference_addressable = 0;
>> +
>> +      /* ipa stack alignment propagation.  */
>> +      if (opts_set->x_flag_ipa_stack_alignment
>> +	  && opts->x_flag_ipa_stack_alignment)
>> +	error_at (loc,
>> +		  "%<-fipa-stack-alignment%> is incompatible with "
>> +		  "%<-flive-patching=inline-only-static|inline-clone%>");
>> +      else
>> +	opts->x_flag_ipa_stack_alignment = 0;
>> 
>> Shall we also disable nothrow or we will worry about C++ only ter?
> 
> This is also mainly for C++ applications, so currently should not be a problem.
> But I can add a separate simple patch to add another flag to control nothrow propagation and disable it when -flive-patching is ON.
> 
>> 
>> Patch is OK,
> 
> thanks for the review.
> 
> I will commit the patch very soon.
> 
> Qing
>> thanks!
>> Honza