On Sun, May 15, 2011 at 3:27 AM, Jan Hubicka <hubi...@ucw.cz> wrote: >> On Fri, May 13, 2011 at 5:54 AM, Paolo Bonzini <bonz...@gnu.org> wrote: >> > On 05/13/2011 03:03 AM, Rong Xu wrote: >> >> >> >> * gcc/coverage.c (revision 173717): set a flag if building >> >> for Linux kernel. >> >> * gcc/tree-profile.c (revision 173717): don't emit TLS >> >> declarations for Linux kernel builds. >> > >> > I think this should be done without touching at all the profiling machinery >> > in GCC. >> > >> > 1) add a new TLS model -ftls-model=none and make the kernel uses it. The >> > model would simply force targetm.have_tls to false. >> > >> >> This is a good idea. >> >> >> > 2) as Richi mentioned, gcov-io and libgcov changes then can move to the >> > kernel, and GCC needs no change at all here. >> > >> >> In fact -- reuse gcc code profiling machinery for FDO is the KEY >> objective in this effort --- the effort tries to minimize gcc changes >> by refactoring gcc code and isolating/abstracting away part of gcc >> implementation that is user space program specific without using >> runtime hooks. Aside from the kernel FDO change -- the refactoring >> itself actually makes the libgcov code more readable -- the existing >> implementation has many huge functions etc. >> >> Kernel source has their implementation of coverage testing -- but it >> makes lots of data structure assumptions and hard coded -- it can >> easily out of sync with gcc and is considered unmaintainable. > > Yep, > I think it does make sense to share the implementation, but we need to find > resonable way to do so. I guess we could separate out the i/o bits > into interface generic enough to cover the needs, move libgcov into its > own directory (just like libgcc is these days) and add an configury option
Honza, Thanks for the comments. Can you elaborate what the options will be look like? -Rong > that sets the interface. The kernel's interface can then be implemented > in a single file instead of tons of ifdefs and I guess can sit either in > kernel > or gcc tree... > > Honza >> >> Rong will have more explanation on the design. >> >> Thanks, >> >> David >> >> >> > BTW, these parts of LIPO: >> > >> >> + if (!is_kernel_build) >> >> + DECL_TLS_MODEL (dc_gcov_type_ptr_var) = >> >> + decl_default_tls_model (dc_gcov_type_ptr_var); >> >> >> >> dc_void_ptr_var = >> >> build_decl (UNKNOWN_LOCATION, VAR_DECL, >> >> @@ -1488,8 +1493,9 @@ >> >> ptr_void); >> >> DECL_ARTIFICIAL (dc_void_ptr_var) = 1; >> >> DECL_EXTERNAL (dc_void_ptr_var) = 1; >> >> - DECL_TLS_MODEL (dc_void_ptr_var) = >> >> - decl_default_tls_model (dc_void_ptr_var); >> >> + if (!is_kernel_build) >> >> + DECL_TLS_MODEL (dc_void_ptr_var) = >> >> + decl_default_tls_model (dc_void_ptr_var); >> > >> > Probably are missing a !targetm.have_tls. >> > >> > Paolo >> > >
