Re: [PATCH 2/4] S390: Use own tbegin macro instead of __builtin_tbegin.

[Stefan Liebler <stli at linux dot vnet dot ibm dot com>]

On 12/22/2016 01:54 PM, Florian Weimer wrote:
> On 12/06/2016 02:51 PM, Stefan Liebler wrote:
>
> > The used inline assembly does not clobber the fprs / vrs!
> > Clobbering the latter ones would force the compiler to save / restore
> > the call saved fprs as those overlap with the vrs, but they only
> > need to be restored if the transaction fails.  Thus the user of the
> > tbegin macros has to compile the file / function with -msoft-float.
> > It prevents gcc from using fprs / vrs.
>
> Is it possible to disable the new macros if the file is not compiled
> with -msoft-float?
Those macros/builtins are only used for the mutex lock elision code in 
elision-*.c files. This code does not use float computation. The 
compiler flag is used to prevent the compiler to perform optimizations 
which use fprs or vrs. At the moment gcc performs no such optimizations.

If you want to use such macros/builtins in other files you'll at least 
have to add -mhtm compiler flag to be able to use those builtins.

Bye
Stefan