[nvptx] Only use one logical barrier resource For openacc loops, we generate this style of code: ... @%r41 bra.uni $L5; @%r40 bra $L6; mov.u64 %r32, %ar0; cvta.shared.u64 %r39, __worker_bcast; st.u64 [%r39], %r32; $L6: $L5: bar.sync 0; @%r40 bra $L4; cvta.shared.u64 %r38, __worker_bcast; ld.u64 %r32, [%r38]; ... $L4: bar.sync 1; ... The first barrier is there to ensure that no thread reads the broadcast buffer before it's written. The second barrier is there to ensure that no thread overwrites the broadcast buffer before all threads have read it (as well as implementing the obligatory synchronization after a worker loop). We've been using the logical barrier resources '0' and '1' for these two barriers, but there's no reason why we can't use the same one. Use logical barrier resource '0' for both barriers, making the openacc implementation claim less resources. Build and reg-tested on x86_64 with nvptx accelerator. 2018-12-17 Tom de Vries * config/nvptx/nvptx.c (nvptx_single): Always pass false to nvptx_wsync. (nvptx_process_pars): Likewise. --- gcc/config/nvptx/nvptx.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/gcc/config/nvptx/nvptx.c b/gcc/config/nvptx/nvptx.c index 9f834d35200..a354811194c 100644 --- a/gcc/config/nvptx/nvptx.c +++ b/gcc/config/nvptx/nvptx.c @@ -4351,7 +4351,7 @@ nvptx_single (unsigned mask, basic_block from, basic_block to) /* This barrier is needed to avoid worker zero clobbering the broadcast buffer before all the other workers have had a chance to read this instance of it. */ - emit_insn_before (nvptx_wsync (true), tail); + emit_insn_before (nvptx_wsync (false), tail); } extract_insn (tail); @@ -4476,7 +4476,7 @@ nvptx_process_pars (parallel *par) { /* Insert begin and end synchronizations. */ emit_insn_before (nvptx_wsync (false), par->forked_insn); - emit_insn_before (nvptx_wsync (true), par->join_insn); + emit_insn_before (nvptx_wsync (false), par->join_insn); } } else if (par->mask & GOMP_DIM_MASK (GOMP_DIM_VECTOR))