On Mon, 9 Nov 2015, Tom de Vries wrote: > On 09/11/15 16:35, Tom de Vries wrote: > > Hi, > > > > this patch series for stage1 trunk adds support to: > > - parallelize oacc kernels regions using parloops, and > > - map the loops onto the oacc gang dimension. > > > > The patch series contains these patches: > > > > 1 Insert new exit block only when needed in > > transform_to_exit_first_loop_alt > > 2 Make create_parallel_loop return void > > 3 Ignore reduction clause on kernels directive > > 4 Implement -foffload-alias > > 5 Add in_oacc_kernels_region in struct loop > > 6 Add pass_oacc_kernels > > 7 Add pass_dominator_oacc_kernels > > 8 Add pass_ch_oacc_kernels > > 9 Add pass_parallelize_loops_oacc_kernels > > 10 Add pass_oacc_kernels pass group in passes.def > > 11 Update testcases after adding kernels pass group > > 12 Handle acc loop directive > > 13 Add c-c++-common/goacc/kernels-*.c > > 14 Add gfortran.dg/goacc/kernels-*.f95 > > 15 Add libgomp.oacc-c-c++-common/kernels-*.c > > 16 Add libgomp.oacc-fortran/kernels-*.f95 > > > > The first 9 patches are more or less independent, but patches 10-16 are > > intended to be committed at the same time. > > > > Bootstrapped and reg-tested on x86_64. > > > > Build and reg-tested with nvidia accelerator, in combination with a > > patch that enables accelerator testing (which is submitted at > > https://gcc.gnu.org/ml/gcc-patches/2015-10/msg01771.html ). > > > > I'll post the individual patches in reply to this message. > > this patch addresses the problem that once the offloading region has been > split off from the original function, alias analysis can no longer use > information available in the original function that would allow it to do a > more precise analysis for the offloading function. [ At some point we could > use fipa-pta for that, as discussed in PR46032, but that's not feasible now. ] > > The basic idea behind the patch is that for typical usage, the base pointers > used in an offloaded region are non-aliasing. The patch works by adding > restrict to the types of the fields used to pass data to an offloading region. > > > The patch implements a new option > -foffload-alias=<none|pointer|all>. > > The option -foffload-alias=none instructs the compiler to assume that > object references and pointer dereferences in an offload region do not > alias. > > The option -foffload-alias=pointer instructs the compiler to assume that > objects references in an offload region do not alias. > > The option -foffload-alias=all instructs the compiler to make no > assumptions about aliasing in offload regions. > > The default value is -foffload-alias=none.
I think global options for this is nonsense. Please follow what we do for #pragma GCC ivdep for example, thus allow the alias behavior to be specified per "region" (whatever makes sense here in the context of offloading). Thanks, Richard. > Thanks, > - Tom > > -- Richard Biener <rguent...@suse.de> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)
