On Wed, May 20, 2020 at 5:56 AM Jiufu Guo via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hi,
>
> In r10-4525, and r10-4161, loop unroller was enabled for simply loops at -O2.
> At the same time, the GIMPLE cunroll is also enabled, while it is not only for
> simple loops. This patch introduces a hook to check if a loop is suitable to
> unroll completely. The hook can be used to check if a loop is simply enough
> for complete unroll, then avoid negative effects like size increasing or
> complex loop unrolling at -O2.
>
> This patch could help to handle the code in PR95018 which contains complex
> loop, and does not cause obvious performance change on SPEC2017.
>
> Bootstrap/regtest pass on powerpc64le. OK for trunk?
I fear you're just digging the rs6000 specific hole you dug up deeper
with this ...
Richard.
> Jiufu
>
> 2020-05-20 Jiufu Guo <guoji...@cn.ibm.com>
>
> PR target/95018
> * target.def (loop_allow_unroll_completely_peel): New hook.
> * doc/tm.texi (TARGET_LOOP_ALLOW_UNROLL_COMPLETELY_PEEL): New hook.
> * doc/tm.texi.in (TARGET_LOOP_ALLOW_UNROLL_COMPLETELY_PEEL): New hook.
> * config/rs6000/rs6000.c (TARGET_LOOP_ALLOW_UNROLL_COMPLETELY_PEEL):
> New hook.
> (rs6000_loop_allow_unroll_completely_peel): New hook implementation.
> * tree-ssa-loop-ivcanon.c (canonicalize_loop_induction_variables):
> Call
> hook loop_allow_unroll_completely_peel.
>
>
> ---
> gcc/config/rs6000/rs6000.c | 19 +++++++++++++++++++
> gcc/doc/tm.texi | 9 +++++++++
> gcc/doc/tm.texi.in | 2 ++
> gcc/target.def | 12 ++++++++++++
> gcc/tree-ssa-loop-ivcanon.c | 5 +++++
> 5 files changed, 47 insertions(+)
>
> diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
> index 8435bc15d72..a1a3f9cb583 100644
> --- a/gcc/config/rs6000/rs6000.c
> +++ b/gcc/config/rs6000/rs6000.c
> @@ -1433,6 +1433,9 @@ static const struct attribute_spec
> rs6000_attribute_table[] =
> #undef TARGET_LOOP_UNROLL_ADJUST
> #define TARGET_LOOP_UNROLL_ADJUST rs6000_loop_unroll_adjust
>
> +#undef TARGET_LOOP_ALLOW_UNROLL_COMPLETELY_PEEL
> +#define TARGET_LOOP_ALLOW_UNROLL_COMPLETELY_PEEL
> rs6000_loop_allow_unroll_completely_peel
> +
> #undef TARGET_INIT_BUILTINS
> #define TARGET_INIT_BUILTINS rs6000_init_builtins
> #undef TARGET_BUILTIN_DECL
> @@ -5139,6 +5142,22 @@ rs6000_loop_unroll_adjust (unsigned nunroll, struct
> loop *loop)
> return nunroll;
> }
>
> +/* Implement targetm.loop_allow_unroll_completely_peel. */
> +
> +static bool
> +rs6000_loop_allow_unroll_completely_peel (HOST_WIDE_INT maxiter, tree niter,
> + struct loop *loop)
> +{
> + if (unroll_only_small_loops && optimize == 2)
> + {
> + if (maxiter >= 4
> + && !(TREE_CODE (niter) == INTEGER_CST && single_exit (loop)))
> + return false;
> + }
> +
> + return true;
> +}
> +
> /* Handler for the Mathematical Acceleration Subsystem (mass) interface to a
> library with vectorized intrinsics. */
>
> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> index 6e7d9dc54a9..f7419872c2f 100644
> --- a/gcc/doc/tm.texi
> +++ b/gcc/doc/tm.texi
> @@ -11893,6 +11893,15 @@ is required only when the target has special
> constraints like maximum
> number of memory accesses.
> @end deftypefn
>
> +@deftypefn {Target Hook} bool TARGET_LOOP_ALLOW_UNROLL_COMPLETELY_PEEL
> (HOST_WIDE_INT @var{maxiter}, tree @var{niter}, class loop *@var{loop})
> +This target hook check if the loop @var{loop} is suitable to unroll
> +completely on the target. The parameter @var{maxiter} is the possible max
> +bound of iterations. The parameter @var{niter} is the number expression of
> +iterations the loop is executed. The parameter @var{loop} is a pointer to
> +the loop. This target hook is required only when the target has special
> +constraints.
> +@end deftypefn
> +
> @defmac POWI_MAX_MULTS
> If defined, this macro is interpreted as a signed integer C expression
> that specifies the maximum number of floating point multiplications
> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
> index 3be984bbd5c..4ae079a650c 100644
> --- a/gcc/doc/tm.texi.in
> +++ b/gcc/doc/tm.texi.in
> @@ -8010,6 +8010,8 @@ lists.
>
> @hook TARGET_LOOP_UNROLL_ADJUST
>
> +@hook TARGET_LOOP_ALLOW_UNROLL_COMPLETELY_PEEL
> +
> @defmac POWI_MAX_MULTS
> If defined, this macro is interpreted as a signed integer C expression
> that specifies the maximum number of floating point multiplications
> diff --git a/gcc/target.def b/gcc/target.def
> index 07059a87caf..3842ba611a2 100644
> --- a/gcc/target.def
> +++ b/gcc/target.def
> @@ -2709,6 +2709,18 @@ number of memory accesses.",
> unsigned, (unsigned nunroll, class loop *loop),
> NULL)
>
> +/* Return if a loop is suitable for complete unroll. */
> +DEFHOOK
> +(loop_allow_unroll_completely_peel,
> + "This target hook check if the loop @var{loop} is suitable to unroll\n\
> +completely on the target. The parameter @var{maxiter} is the possible max\n\
> +bound of iterations. The parameter @var{niter} is the number expression of\n\
> +iterations the loop is executed. The parameter @var{loop} is a pointer to\n\
> +the loop. This target hook is required only when the target has special\n\
> +constraints.",
> + bool, (HOST_WIDE_INT maxiter, tree niter, class loop *loop),
> + NULL)
> +
> /* True if X is a legitimate MODE-mode immediate operand. */
> DEFHOOK
> (legitimate_constant_p,
> diff --git a/gcc/tree-ssa-loop-ivcanon.c b/gcc/tree-ssa-loop-ivcanon.c
> index 8ab6ab3330c..52d45a90a56 100644
> --- a/gcc/tree-ssa-loop-ivcanon.c
> +++ b/gcc/tree-ssa-loop-ivcanon.c
> @@ -39,6 +39,7 @@ along with GCC; see the file COPYING3. If not see
> #include "system.h"
> #include "coretypes.h"
> #include "backend.h"
> +#include "target.h"
> #include "tree.h"
> #include "gimple.h"
> #include "cfghooks.h"
> @@ -1231,6 +1232,10 @@ canonicalize_loop_induction_variables (class loop
> *loop,
> /* Force re-computation of loop bounds so we can remove redundant exits.
> */
> maxiter = max_loop_iterations_int (loop);
>
> + if (allow_peel && targetm.loop_allow_unroll_completely_peel
> + && !targetm.loop_allow_unroll_completely_peel (maxiter, niter, loop))
> + return false;
> +
> if (dump_file && (dump_flags & TDF_DETAILS)
> && TREE_CODE (niter) == INTEGER_CST)
> {
> --
> 2.17.1
>
