Ping - as this patch addresses a wrong-code issue in new functionality, I'd like
to ask if it may be applied to gcc-7 branch too.
On Fri, 7 Apr 2017, Alexander Monakov wrote:
> Ping.
>
> > I've noticed while re-reading that this patch incorrectly handled SIMT case
> > in lower_lastprivate_clauses. The code was changed to look for variables
> > with "omp simt private" attribute, and was left under
> > 'simduid && DECL_HAS_VALUE_EXPR_P (new_var)' condition. This effectively
> > constrained processing to privatized (i.e. addressable) variables, as
> > non-addressable variables now have neither the value-expr nor the attribute.
> >
> > This wasn't caught in testing, as apparently all testcases that have target
> > simd loops with linear/lastprivate clauses also have the corresponding
> > variables
> > mentioned in target map clause, which makes them addressable (is that
> > necessary?),
> > and I didn't think to check something like that manually.
> >
> > The following patch fixes it by adjusting the if's in
> > lower_lastprivate_clauses;
> > alternatively it may be possible to keep that code as-is, and instead set up
> > value-expr and "omp simt private" attributes for all formally private
> > variables,
> > not just addressable ones, but to me that sounds less preferable. OK for
> > trunk?
> >
> > I think it's possible to improve test coverage for NVPTX by running all
> > OpenMP
> > testcases via nvptx-none-run (it'll need some changes, but shouldn't be
> > hard).
> >
> > gcc/
> > * omp-low.c (lower_lastprivate_clauses): Correct handling of linear and
> > lastprivate clauses in SIMT case.
> >
> > libgomp/
> > * testsuite/libgomp.c/target-36.c: New testcase.
> >
> > Thanks.
> > Alexander
> >
> > diff --git a/gcc/omp-low.c b/gcc/omp-low.c
> > index 253dc85..02b681c 100644
> > --- a/gcc/omp-low.c
> > +++ b/gcc/omp-low.c
> > @@ -4768,11 +4768,10 @@ lower_lastprivate_clauses (tree clauses, tree
> > predicate, gimple_seq *stmt_list,
> > TREE_NO_WARNING (new_var) = 1;
> > }
> >
> > - if (simduid && DECL_HAS_VALUE_EXPR_P (new_var))
> > + if (!maybe_simt && simduid && DECL_HAS_VALUE_EXPR_P (new_var))
> > {
> > tree val = DECL_VALUE_EXPR (new_var);
> > - if (!maybe_simt
> > - && TREE_CODE (val) == ARRAY_REF
> > + if (TREE_CODE (val) == ARRAY_REF
> > && VAR_P (TREE_OPERAND (val, 0))
> > && lookup_attribute ("omp simd array",
> > DECL_ATTRIBUTES (TREE_OPERAND (val,
> > @@ -4792,26 +4791,26 @@ lower_lastprivate_clauses (tree clauses, tree
> > predicate, gimple_seq *stmt_list,
> > TREE_OPERAND (val, 0), lastlane,
> > NULL_TREE, NULL_TREE);
> > }
> > - else if (maybe_simt
> > - && VAR_P (val)
> > - && lookup_attribute ("omp simt private",
> > - DECL_ATTRIBUTES (val)))
> > + }
> > + else if (maybe_simt)
> > + {
> > + tree val = (DECL_HAS_VALUE_EXPR_P (new_var)
> > + ? DECL_VALUE_EXPR (new_var)
> > + : new_var);
> > + if (simtlast == NULL)
> > {
> > - if (simtlast == NULL)
> > - {
> > - simtlast = create_tmp_var (unsigned_type_node);
> > - gcall *g = gimple_build_call_internal
> > - (IFN_GOMP_SIMT_LAST_LANE, 1, simtcond);
> > - gimple_call_set_lhs (g, simtlast);
> > - gimple_seq_add_stmt (stmt_list, g);
> > - }
> > - x = build_call_expr_internal_loc
> > - (UNKNOWN_LOCATION, IFN_GOMP_SIMT_XCHG_IDX,
> > - TREE_TYPE (val), 2, val, simtlast);
> > - new_var = unshare_expr (new_var);
> > - gimplify_assign (new_var, x, stmt_list);
> > - new_var = unshare_expr (new_var);
> > + simtlast = create_tmp_var (unsigned_type_node);
> > + gcall *g = gimple_build_call_internal
> > + (IFN_GOMP_SIMT_LAST_LANE, 1, simtcond);
> > + gimple_call_set_lhs (g, simtlast);
> > + gimple_seq_add_stmt (stmt_list, g);
> > }
> > + x = build_call_expr_internal_loc
> > + (UNKNOWN_LOCATION, IFN_GOMP_SIMT_XCHG_IDX,
> > + TREE_TYPE (val), 2, val, simtlast);
> > + new_var = unshare_expr (new_var);
> > + gimplify_assign (new_var, x, stmt_list);
> > + new_var = unshare_expr (new_var);
> > }
> >
> > if (OMP_CLAUSE_CODE (c) == OMP_CLAUSE_LASTPRIVATE
> > diff --git a/libgomp/testsuite/libgomp.c/target-36.c
> > b/libgomp/testsuite/libgomp.c/target-36.c
> > new file mode 100644
> > index 0000000..6925a2a
> > --- /dev/null
> > +++ b/libgomp/testsuite/libgomp.c/target-36.c
> > @@ -0,0 +1,18 @@
> > +int
> > +main ()
> > +{
> > + int ah, bh, n = 1024;
> > +#pragma omp target map(from: ah, bh)
> > + {
> > + int a, b;
> > +#pragma omp simd lastprivate(b)
> > + for (a = 0; a < n; a++)
> > + {
> > + b = a + n + 1;
> > + asm volatile ("" : "+r"(b));
> > + }
> > + ah = a, bh = b;
> > + }
> > + if (ah != n || bh != 2 * n)
> > + __builtin_abort ();
> > +}
> >
>
