On Mon, 9 Nov 2015, Martin Jambor wrote:
> Hi,
>
> On Fri, Nov 06, 2015 at 09:42:25AM +0100, Richard Biener wrote:
> > On Thu, 5 Nov 2015, Martin Jambor wrote:
> >
> > > Hi,
> > >
> > > the following small part of the merge deals with new options. It adds
> > > four independent things:
> > >
> > > 1) flag_disable_hsa is used by code in opts.c (in the first patch) to
> > > remember whether HSA has been explicitely disabled on the compiler
> > > command line.
> >
> > But I don't see any way to disable it on the command line? (no switch?)
>
> No, the switch is -foffload, which has missing documentation (PR
> 67300) and is only described at https://gcc.gnu.org/wiki/Offloading
> Nevertheless, the option allows the user to specify compiler option
> -foffload=disable and no offloading should happen, not even HSA. The
> user can also enumerate just the offload targets they want (and pass
> them special command line stuff).
>
> It seems I have misplaced a hunk in the patch series. Nevertheless,
> in the first patch (with configuration stuff), there is a change to
> opts.c which scans the -foffload= contents and sets the flag variable
> if hsa is not present.
>
> Whenever the compiler has to decide whether HSA is enabled for the
> given compilation or not, it has to look at this variable (if
> configured for HSA).
>
> >
> > > 2) -Whsa is a new warning we emit whenever we fail to produce HSAIL
> > > for some source code. It is on by default but of course only
> > > emitted by HSAIL generating code so should never affect anybody who
> > > does not use HSA-enabled compiler and OpenMP 4 device constructs.
> > >
> > > We have found the following two additions very useful for debugging on
> > > the branch but will understand if they are not deemed suitable for
> > > trunk and will gladly remove them:
> > >
> > > 3) -fdisable-hsa-gridification disables the gridification process to
> > > ease experimenting with dynamic parallelism. With this option,
> > > HSAIL is always generated from the CPU-intended gimple.
> >
> > So this sounds like sth a user should never do which means
> > it shouln't be a switch (but a parameter or removed).
>
> Martin said he likes the capability to switch gridification off so I
> turned it into a parameter.
>
> >
> > > 4) Parameter hsa-gen-debug-stores will be obsolete once HSA run-time
> > > supports debugging traps. Before that, we have to do with
> > > debugging stores to memory at defined places, which however can
> > > cost speed in benchmarks. So they are only enabled with this
> > > parameter. We decided to make it a parameter rather than a switch
> > > to emphasize the fact it will go away and to possibly allow us
> > > select different levels of verbosity of the stores in the future).
> >
> > You miss documentation in invoke.texi for new switches and parameters.
>
> Right, I have added that together with other changes addressing the
> above comments and am about to commit the following to the branch:
Looks good to me.
Thanks,
Richard.
>
> 2015-11-09 Martin Jambor <mjam...@suse.cz>
>
> * common.opt (-fdisable-hsa-gridification): Removed.
> * params.def (PARAM_OMP_GPU_GRIDIFY): New.
> * omp-low.c: Include params.h.
> (execute_lower_omp): Check parameter PARAM_OMP_GPU_GRIDIFY instead of
> flag_disable-hsa-gridification.
> * doc/invoke.texi (Optimize Options): Add description of
> omp-gpu-gridify and hsa-gen-debug-stores parameters.
>
> diff --git a/gcc/common.opt b/gcc/common.opt
> index 9cb52db..8bee504 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -1115,10 +1115,6 @@ fdiagnostics-show-location=
> Common Joined RejectNegative Enum(diagnostic_prefixing_rule)
> -fdiagnostics-show-location=[once|every-line] How often to emit
> source location at the beginning of line-wrapped diagnostics.
>
> -fdisable-hsa-gridification
> -Common Report Var(flag_disable_hsa_gridification)
> -Disable HSA gridification for OMP pragmas
> -
> ; Required for these enum values.
> SourceInclude
> pretty-print.h
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 4fc7d88..b9fb1e1 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -11171,6 +11171,17 @@ dynamic, guided, auto, runtime). The default is
> static.
> Maximum depth of recursion when querying properties of SSA names in things
> like fold routines. One level of recursion corresponds to following a
> use-def chain.
> +
> +@item omp-gpu-gridify
> +Enable creation of gridified GPU kernels out of loops within target
> +OpenMP constructs. This conversion is enabled by default when
> +offloading to HSA, to disable it, use @option{--param omp-gpu-gridify=0}
> +
> +@item hsa-gen-debug-stores
> +Enable emission of special debug stores within HSA kernels which are
> +then read and reported by libgomp plugin. Generation of these stores
> +is disabled by default, use @option{--param hsa-gen-debug-stores=1} to
> +enable it.
> @end table
> @end table
>
> diff --git a/gcc/omp-low.c b/gcc/omp-low.c
> index 34aafc8..f90a698 100644
> --- a/gcc/omp-low.c
> +++ b/gcc/omp-low.c
> @@ -82,6 +82,7 @@ along with GCC; see the file COPYING3. If not see
> #include "gimple-pretty-print.h"
> #include "symbol-summary.h"
> #include "hsa.h"
> +#include "params.h"
>
> /* Lowering of OMP parallel and workshare constructs proceeds in two
> phases. The first phase scans the function looking for OMP statements
> @@ -17449,7 +17450,8 @@ execute_lower_omp (void)
>
> body = gimple_body (current_function_decl);
>
> - if (hsa_gen_requested_p () && !flag_disable_hsa_gridification)
> + if (hsa_gen_requested_p ()
> + && PARAM_VALUE (PARAM_OMP_GPU_GRIDIFY) == 1)
> create_target_gpukernels (&body);
>
> scan_omp (&body, NULL);
> diff --git a/gcc/params.def b/gcc/params.def
> index 86911e2..f12755b 100644
> --- a/gcc/params.def
> +++ b/gcc/params.def
> @@ -1178,6 +1178,12 @@ DEFPARAM (PARAM_MAX_SSA_NAME_QUERY_DEPTH,
> " SSA name.",
> 2, 1, 0)
>
> +DEFPARAM (PARAM_OMP_GPU_GRIDIFY,
> + "omp-gpu-gridify",
> + "Enable creation of gridified GPU kernels out of OpenMP target "
> + "constructs",
> + 1, 0, 1)
> +
> DEFPARAM (PARAM_HSA_GEN_DEBUG_STORES,
> "hsa-gen-debug-stores",
> "Level of hsa debug stores verbosity",
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
