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openmp: Improve expand_omp_atomic_pipeline

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When __atomic_* builtins were introduced, omp-expand.c (omp-low.c
at that point) has been adjusted in several spots so that it uses
the atomic builtins instead of sync builtins, but
expand_omp_atomic_pipeline has not because the __atomic_compare_exchange_*
APIs take address of the argument, so it kept using __sync_val_compare_swap_*.
That means it always uses seq_cst though.
This patch changes it to use the ATOMIC_COMPARE_EXCHANGE ifn which gimple-fold
folds __atomic_compare_exchange_* into - that ifn also passes expected
directly.

2021-09-03  Jakub Jelinek  <jakub@redhat.com>

	* omp-expand.c (expand_omp_atomic_pipeline): Use
	IFN_ATOMIC_COMPARE_EXCHANGE instead of
	BUILT_IN_SYNC_VAL_COMPARE_AND_SWAP_? so that memory order
	can be provided.
This commit is contained in:
Jakub Jelinek 2021-09-03 09:54:58 +02:00
parent e902136b31
commit 090f0d78f1
1 changed files with 18 additions and 3 deletions
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21
gcc/omp-expand.c
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@ -8807,8 +8807,6 @@ expand_omp_atomic_pipeline (basic_block load_bb, basic_block store_bb,
edge e;
enum built_in_function fncode;
/* ??? We need a non-pointer interface to __atomic_compare_exchange in
order to use the RELAXED memory model effectively. */
fncode = (enum built_in_function)((int)BUILT_IN_SYNC_VAL_COMPARE_AND_SWAP_N
+ index + 1);
cmpxchg = builtin_decl_explicit (fncode);
@ -8825,6 +8823,15 @@ expand_omp_atomic_pipeline (basic_block load_bb, basic_block store_bb,
/* Load the initial value, replacing the GIMPLE_OMP_ATOMIC_LOAD. */
si = gsi_last_nondebug_bb (load_bb);
gcc_assert (gimple_code (gsi_stmt (si)) == GIMPLE_OMP_ATOMIC_LOAD);
location_t loc = gimple_location (gsi_stmt (si));
enum omp_memory_order omo = gimple_omp_atomic_memory_order (gsi_stmt (si));
enum memmodel imo = omp_memory_order_to_memmodel (omo);
tree mo = build_int_cst (NULL, imo);
if (imo == MEMMODEL_RELEASE)
imo = MEMMODEL_RELAXED;
else if (imo == MEMMODEL_ACQ_REL)
imo = MEMMODEL_ACQUIRE;
tree fmo = build_int_cst (NULL, imo);
/* For floating-point values, we'll need to view-convert them to integers
so that we can perform the atomic compare and swap. Simplify the
@ -8921,7 +8928,15 @@ expand_omp_atomic_pipeline (basic_block load_bb, basic_block store_bb,
GSI_SAME_STMT);
/* Build the compare&swap statement. */
new_storedi = build_call_expr (cmpxchg, 3, iaddr, loadedi, storedi);
tree ctype = build_complex_type (itype);
int flag = int_size_in_bytes (itype);
new_storedi = build_call_expr_internal_loc (loc, IFN_ATOMIC_COMPARE_EXCHANGE,
ctype, 6, iaddr, loadedi,
storedi,
build_int_cst (integer_type_node,
flag),
mo, fmo);
new_storedi = build1 (REALPART_EXPR, itype, new_storedi);
new_storedi = force_gimple_operand_gsi (&si,
fold_convert (TREE_TYPE (loadedi),
new_storedi),