On Fri, 31 May 2019, Jakub Jelinek wrote:
> Hi!
>
> As a preparation for lastprivate(conditional:) on #pragma omp simd, I need
> if-conversion to handle "omp simd array" accesses. These are safe, no
> matter whether written or read, each simd lane accesses their own element,
> after the vectorization it is all just a single vector read or store or RMW
> cycle, it will never trap (it is an automatic variable), it will never be
> out of bounds (the index is guaranteed to be within the bounds of the array,
> as the array is sized to the vectorization factor and index is the simd lane
> number within that vectorization factor).
>
> Tested on x86_64-linux with vect.exp, ok for trunk if it passes full
> bootstrap/regtest?
Hmm. Is it enough to set TREE_THIS_NOTRAP on the ARRAY_REF instead?
At least it's documented the ARRAY_REF then isn't the issue.
As for conditional vs. unconditional I'm not so sure but automatic
vars are excepmted from that anyways?
Richard.
> 2019-05-31 Jakub Jelinek <ja...@redhat.com>
>
> * tree-if-conv.c: Include attribs.h.
> (ifcvt_memrefs_wont_trap): Return true for ARRAY_REF access to
> "omp simd array" variable with .GOMP_SIMD_LANE as index.
>
> * gcc.dg/vect/vect-cond-12.c: New test.
>
> --- gcc/tree-if-conv.c.jj 2019-05-14 21:37:32.932400472 +0200
> +++ gcc/tree-if-conv.c 2019-05-31 11:13:13.558732900 +0200
> @@ -120,6 +120,7 @@ along with GCC; see the file COPYING3.
> #include "fold-const.h"
> #include "tree-ssa-sccvn.h"
> #include "tree-cfgcleanup.h"
> +#include "attribs.h"
>
> /* Only handle PHIs with no more arguments unless we are asked to by
> simd pragma. */
> @@ -897,6 +898,32 @@ ifcvt_memrefs_wont_trap (gimple *stmt, v
> if (DR_W_UNCONDITIONALLY (*master_dr))
> return true;
>
> + /* OpenMP simd lane accesses to omp simd array variables are always
> + within bounds and can be handled as if it was unconditional. */
> + tree base_var = get_base_address (base);
> + if (VAR_P (base_var)
> + && lookup_attribute ("omp simd array", DECL_ATTRIBUTES (base_var)))
> + {
> + tree ref = DR_REF (a);
> + struct loop *loop = loop_containing_stmt (stmt);
> + if (loop->simduid
> + && TREE_CODE (ref) == ARRAY_REF
> + && TREE_CODE (TREE_OPERAND (ref, 1)) == SSA_NAME)
> + {
> + gimple *def = SSA_NAME_DEF_STMT (TREE_OPERAND (ref, 1));
> + if (is_gimple_call (def)
> + && gimple_call_internal_p (def)
> + && (gimple_call_internal_fn (def) == IFN_GOMP_SIMD_LANE))
> + {
> + tree arg = gimple_call_arg (def, 0);
> + gcc_assert (TREE_CODE (arg) == SSA_NAME);
> + arg = SSA_NAME_VAR (arg);
> + if (arg == loop->simduid)
> + return true;
> + }
> + }
> + }
> +
> /* If a is unconditionally accessed then ...
>
> Even a is conditional access, we can treat it as an unconditional
> --- gcc/testsuite/gcc.dg/vect/vect-cond-12.c.jj 2019-05-31
> 11:25:33.203577504 +0200
> +++ gcc/testsuite/gcc.dg/vect/vect-cond-12.c 2019-05-31 11:26:58.616174115
> +0200
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +/* { dg-additional-options "-fopenmp-simd" } */
> +/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" { target
> vect_condition } } } */
> +
> +int x;
> +
> +void
> +foo (int *a)
> +{
> + #pragma omp simd lastprivate (x)
> + for (int i = 0; i < 1024; ++i)
> + if (a[i])
> + x = i;
> +}
>
> Jakub
>
--
Richard Biener <rguent...@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)
