openmp: Implement OpenMP 5.1 atomics, so far for C only

This patch implements OpenMP 5.1 atomics (with clarifications from upcoming 5.2).
The most important changes are that it is now possible to write (for C/C++,
for Fortran it was possible before already) min/max atomics and more importantly
compare and exchange in various forms.
Also, acq_rel is now allowed on read/write and acq_rel/acquire are allowed on
update, and there are new compare, weak and fail clauses.

2021-09-10  Jakub Jelinek  <jakub@redhat.com>

gcc/
	* tree-core.h (enum omp_memory_order): Add OMP_MEMORY_ORDER_MASK,
	OMP_FAIL_MEMORY_ORDER_UNSPECIFIED, OMP_FAIL_MEMORY_ORDER_RELAXED,
	OMP_FAIL_MEMORY_ORDER_ACQUIRE, OMP_FAIL_MEMORY_ORDER_RELEASE,
	OMP_FAIL_MEMORY_ORDER_ACQ_REL, OMP_FAIL_MEMORY_ORDER_SEQ_CST and
	OMP_FAIL_MEMORY_ORDER_MASK enumerators.
	(OMP_FAIL_MEMORY_ORDER_SHIFT): Define.
	* gimple-pretty-print.c (dump_gimple_omp_atomic_load,
	dump_gimple_omp_atomic_store): Print [weak] for weak atomic
	load/store.
	* gimple.h (enum gf_mask): Change GF_OMP_ATOMIC_MEMORY_ORDER
	to 6-bit mask, adjust GF_OMP_ATOMIC_NEED_VALUE value and add
	GF_OMP_ATOMIC_WEAK.
	(gimple_omp_atomic_weak_p, gimple_omp_atomic_set_weak): New inline
	functions.
	* tree.h (OMP_ATOMIC_WEAK): Define.
	* tree-pretty-print.c (dump_omp_atomic_memory_order): Adjust for
	fail memory order being encoded in the same enum and also print
	fail clause if present.
	(dump_generic_node): Print weak clause if OMP_ATOMIC_WEAK.
	* gimplify.c (goa_stabilize_expr): Add target_expr and rhs arguments,
	handle pre_p == NULL case as a test mode that only returns value
	but doesn't change gimplify nor change anything otherwise, adjust
	recursive calls, add MODIFY_EXPR, ADDR_EXPR, COND_EXPR, TARGET_EXPR
	and CALL_EXPR handling, adjust COMPOUND_EXPR handling for
	__builtin_clear_padding calls, for !rhs gimplify as lvalue rather
	than rvalue.
	(gimplify_omp_atomic): Adjust goa_stabilize_expr caller.  Handle
	COND_EXPR rhs.  Set weak flag on gimple load/store for
	OMP_ATOMIC_WEAK.
	* omp-expand.c (omp_memory_order_to_fail_memmodel): New function.
	(omp_memory_order_to_memmodel): Adjust for fail clause encoded
	in the same enum.
	(expand_omp_atomic_cas): New function.
	(expand_omp_atomic_pipeline): Use omp_memory_order_to_fail_memmodel
	function.
	(expand_omp_atomic): Attempt to optimize atomic compare and exchange
	using expand_omp_atomic_cas.
gcc/c-family/
	* c-common.h (c_finish_omp_atomic): Add r and weak arguments.
	* c-omp.c: Include gimple-fold.h.
	(c_finish_omp_atomic): Add r and weak arguments.  Add support for
	OpenMP 5.1 atomics.
gcc/c/
	* c-parser.c (c_parser_conditional_expression): If omp_atomic_lhs and
	cond.value is >, < or == with omp_atomic_lhs as one of the operands,
	don't call build_conditional_expr, instead build a COND_EXPR directly.
	(c_parser_binary_expression): Avoid calling parser_build_binary_op
	if omp_atomic_lhs even in more cases for >, < or ==.
	(c_parser_omp_atomic): Update function comment for OpenMP 5.1 atomics,
	parse OpenMP 5.1 atomics and fail, compare and weak clauses, allow
	acq_rel on atomic read/write and acq_rel/acquire clauses on update.
	* c-typeck.c (build_binary_op): For flag_openmp only handle
	MIN_EXPR/MAX_EXPR.
gcc/cp/
	* parser.c (cp_parser_omp_atomic): Allow acq_rel on atomic read/write
	and acq_rel/acquire clauses on update.
	* semantics.c (finish_omp_atomic): Adjust c_finish_omp_atomic caller.
gcc/testsuite/
	* c-c++-common/gomp/atomic-17.c (foo): Add tests for atomic read,
	write or update with acq_rel clause and atomic update with acquire clause.
	* c-c++-common/gomp/atomic-18.c (foo): Adjust expected diagnostics
	wording, remove tests moved to atomic-17.c.
	* c-c++-common/gomp/atomic-21.c: Expect only 2 omp atomic release and
	2 omp atomic acq_rel directives instead of 4 omp atomic release.
	* c-c++-common/gomp/atomic-25.c: New test.
	* c-c++-common/gomp/atomic-26.c: New test.
	* c-c++-common/gomp/atomic-27.c: New test.
	* c-c++-common/gomp/atomic-28.c: New test.
	* c-c++-common/gomp/atomic-29.c: New test.
	* c-c++-common/gomp/atomic-30.c: New test.
	* c-c++-common/goacc-gomp/atomic.c: Expect 1 omp atomic release and
	1 omp atomic_acq_rel instead of 2 omp atomic release directives.
	* gcc.dg/gomp/atomic-5.c: Adjust expected error diagnostic wording.
	* g++.dg/gomp/atomic-18.C:Expect 4 omp atomic release and
	1 omp atomic_acq_rel instead of 5 omp atomic release directives.
libgomp/
	* testsuite/libgomp.c-c++-common/atomic-19.c: New test.
	* testsuite/libgomp.c-c++-common/atomic-20.c: New test.
	* testsuite/libgomp.c-c++-common/atomic-21.c: New test.

1 files changed, 203 insertions, 0 deletions

diff --git a/libgomp/testsuite/libgomp.c-c++-common/atomic-20.c b/libgomp/testsuite/libgomp.c-c++-common/atomic-20.c
new file mode 100644
index 0000000..571a714
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c-c++-common/atomic-20.c
@@ -0,0 +1,203 @@
+// { dg-do run { target c } }
+
+extern
+#ifdef __cplusplus
+"C"
+#endif
+void abort (void);
+float x = 6.0f;
+
+int
+main ()
+{
+  float v;
+  int r;
+  #pragma omp atomic compare
+  x = x > 8.0f ? 8.0f : x;
+  #pragma omp atomic read
+  v = x;
+  if (v != 6.0f)
+    abort ();
+  #pragma omp atomic compare
+  x = x > 4.0f ? 4.0f : x;
+  #pragma omp atomic read
+  v = x;
+  if (v != 4.0f)
+    abort ();
+  #pragma omp atomic compare capture
+  v = x = x < 8.0f ? 8.0f : x;
+  if (v != 8.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 8)
+    abort ();
+  #pragma omp atomic capture compare
+  { v = x; x = x < 12.0f ? 12.0f : x; }
+  if (v != 8.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 12.0f)
+    abort ();
+  #pragma omp atomic capture compare
+  { v = x; x = x < 4.0f ? 4.0f : x; }
+  if (v != 12.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 12.0f)
+    abort ();
+  #pragma omp atomic compare
+  x = x == 12.0 ? 16.0L : x;
+  #pragma omp atomic read
+  v = x;
+  if (v != 16.0)
+    abort ();
+  r = 57;
+  #pragma omp atomic compare capture
+  v = x = x == 15.0f ? r + 7.0f : x;
+  if (v != 16.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 16.0f)
+    abort ();
+  #pragma omp atomic capture, update, compare seq_cst fail(acquire)
+  { v = x; x = x == 73.0L - r ? 12.0f : x; }
+  if (v != 16.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 12.0f)
+    abort ();
+  #pragma omp atomic update, compare, capture
+  { x = x == 69.0 - r ? 6.0f : x; v = x; }
+  if (v != 6.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 6.0f)
+    abort ();
+  #pragma omp atomic compare
+  if (x > 8.0f) { x = 8.0f; }
+  #pragma omp atomic read
+  v = x;
+  if (v != 6.0f)
+    abort ();
+  #pragma omp atomic compare
+  if (x > 4.0) { x = 4.0; }
+  #pragma omp atomic read
+  v = x;
+  if (v != 4.0f)
+    abort ();
+  #pragma omp atomic compare capture
+  { if (x < 8.0f) { x = 8.0f; } v = x; }
+  if (v != 8.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 8.0f)
+    abort ();
+  #pragma omp atomic capture compare
+  { v = x; if (x < 12.0f) { x = 12.0f; } }
+  if (v != 8.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 12.0f)
+    abort ();
+  #pragma omp atomic capture compare
+  { v = x; if (x < 4.0L) { x = 4.0L; } }
+  if (v != 12.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 12.0f)
+    abort ();
+  #pragma omp atomic compare
+  if (x == 12.0f) { x = 16.0L; }
+  #pragma omp atomic read
+  v = x;
+  if (v != 16.0f)
+    abort ();
+  r = 57.0;
+  #pragma omp atomic compare capture
+  { if (x == 15.0f) { x = r + 7.0f; } v = x; }
+  if (v != 16.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 16.0f)
+    abort ();
+  #pragma omp atomic capture, update, compare seq_cst fail(acquire)
+  { v = x; if (x == 73.0L - r) { x = 12.0L; } }
+  if (v != 16.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 12.0f)
+    abort ();
+  #pragma omp atomic update, compare, capture
+  { if (x == 69.0L - r) { x = 6.0; } v = x; }
+  if (v != 6.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 6.0f)
+    abort ();
+  v = 24;
+  #pragma omp atomic compare capture
+  if (x == 12.0f) { x = 16.0f; } else { v = x; }
+  if (v != 6.0f)
+    abort ();
+  v = 32.0f;
+  #pragma omp atomic read
+  v = x;
+  if (v != 6.0f)
+    abort ();
+  v = 147.0f;
+  #pragma omp atomic capture compare
+  if (x == 6.0f) { x = 57.0f; } else { v = x; }
+  if (v != 147.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 57.0f)
+    abort ();
+  #pragma omp atomic update, capture, compare, weak, seq_cst, fail (relaxed)
+  { r = x == 137.0f; if (r) { x = 174.0f; } }
+  if (r)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 57.0f)
+    abort ();
+  #pragma omp atomic compare capture fail (relaxed)
+  { r = x == 57.0f; if (r) { x = 6.0f; } }
+  if (r != 1)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 6.0f)
+    abort ();
+  v = -5.0f;
+  #pragma omp atomic capture compare
+  { r = x == 17.0L; if (r) { x = 25.0; } else { v = x; } }
+  if (r || v != 6.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 6.0f)
+    abort ();
+  v = 15.0f;
+  #pragma omp atomic capture compare
+  { r = x == 6.0f; if (r) { x = 23.0f; } else { v = x; } }
+  if (r != 1 || v != 15.0f)
+    abort ();
+  #pragma omp atomic read
+  v = x;
+  if (v != 23.0f)
+    abort ();
+  return 0;
+}