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, 167 insertions, 6 deletions

diff --git a/gcc/c-family/c-omp.c b/gcc/c-family/c-omp.c
index 4b95fc1..75184a3 100644
--- a/gcc/c-family/c-omp.c
+++ b/gcc/c-family/c-omp.c
@@ -36,6 +36,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimplify.h"
 #include "langhooks.h"
 #include "bitmap.h"
+#include "gimple-fold.h"
 
 
 /* Complete a #pragma oacc wait construct.  LOC is the location of
@@ -215,15 +216,17 @@ c_finish_omp_taskyield (location_t loc)
 tree
 c_finish_omp_atomic (location_t loc, enum tree_code code,
 		     enum tree_code opcode, tree lhs, tree rhs,
-		     tree v, tree lhs1, tree rhs1, bool swapped,
-		     enum omp_memory_order memory_order, bool test)
+		     tree v, tree lhs1, tree rhs1, tree r, bool swapped,
+		     enum omp_memory_order memory_order, bool weak,
+		     bool test)
 {
-  tree x, type, addr, pre = NULL_TREE;
+  tree x, type, addr, pre = NULL_TREE, rtmp = NULL_TREE, vtmp = NULL_TREE;
   HOST_WIDE_INT bitpos = 0, bitsize = 0;
+  enum tree_code orig_opcode = opcode;
 
   if (lhs == error_mark_node || rhs == error_mark_node
       || v == error_mark_node || lhs1 == error_mark_node
-      || rhs1 == error_mark_node)
+      || rhs1 == error_mark_node || r == error_mark_node)
     return error_mark_node;
 
   /* ??? According to one reading of the OpenMP spec, complex type are
@@ -243,6 +246,12 @@ c_finish_omp_atomic (location_t loc, enum tree_code code,
       error_at (loc, "%<_Atomic%> expression in %<#pragma omp atomic%>");
       return error_mark_node;
     }
+  if (r && r != void_list_node && !INTEGRAL_TYPE_P (TREE_TYPE (r)))
+    {
+      error_at (loc, "%<#pragma omp atomic compare capture%> with non-integral "
+		     "comparison result");
+      return error_mark_node;
+    }
 
   if (opcode == RDIV_EXPR)
     opcode = TRUNC_DIV_EXPR;
@@ -299,6 +308,7 @@ c_finish_omp_atomic (location_t loc, enum tree_code code,
       x = build1 (OMP_ATOMIC_READ, type, addr);
       SET_EXPR_LOCATION (x, loc);
       OMP_ATOMIC_MEMORY_ORDER (x) = memory_order;
+      gcc_assert (!weak);
       if (blhs)
 	x = build3_loc (loc, BIT_FIELD_REF, TREE_TYPE (blhs), x,
 			bitsize_int (bitsize), bitsize_int (bitpos));
@@ -313,12 +323,29 @@ c_finish_omp_atomic (location_t loc, enum tree_code code,
     {
       lhs = build3_loc (loc, BIT_FIELD_REF, TREE_TYPE (blhs), lhs,
 			bitsize_int (bitsize), bitsize_int (bitpos));
-      if (swapped)
+      if (opcode == COND_EXPR)
+	{
+	  bool save = in_late_binary_op;
+	  in_late_binary_op = true;
+	  std::swap (rhs, rhs1);
+	  rhs1 = build_binary_op (loc, EQ_EXPR, lhs, rhs1, true);
+	  in_late_binary_op = save;
+	}
+      else if (swapped)
 	rhs = build_binary_op (loc, opcode, rhs, lhs, true);
       else if (opcode != NOP_EXPR)
 	rhs = build_binary_op (loc, opcode, lhs, rhs, true);
       opcode = NOP_EXPR;
     }
+  else if (opcode == COND_EXPR)
+    {
+      bool save = in_late_binary_op;
+      in_late_binary_op = true;
+      std::swap (rhs, rhs1);
+      rhs1 = build_binary_op (loc, EQ_EXPR, lhs, rhs1, true);
+      in_late_binary_op = save;
+      opcode = NOP_EXPR;
+    }
   else if (swapped)
     {
       rhs = build_binary_op (loc, opcode, rhs, lhs, true);
@@ -343,6 +370,100 @@ c_finish_omp_atomic (location_t loc, enum tree_code code,
   if (blhs)
     rhs = build3_loc (loc, BIT_INSERT_EXPR, type, new_lhs,
 		      rhs, bitsize_int (bitpos));
+  if (orig_opcode == COND_EXPR)
+    {
+      if (error_operand_p (rhs1))
+	return error_mark_node;
+      gcc_assert (TREE_CODE (rhs1) == EQ_EXPR);
+      tree cmptype = TREE_TYPE (TREE_OPERAND (rhs1, 0));
+      if (SCALAR_FLOAT_TYPE_P (cmptype))
+	{
+	  bool clear_padding = false;
+	  if (BITS_PER_UNIT == 8 && CHAR_BIT == 8)
+	    {
+	      HOST_WIDE_INT sz = int_size_in_bytes (cmptype), i;
+	      gcc_assert (sz > 0);
+	      unsigned char *buf = XALLOCAVEC (unsigned char, sz);
+	      memset (buf, ~0, sz);
+	      clear_type_padding_in_mask (cmptype, buf);
+	      for (i = 0; i < sz; i++)
+		if (buf[i] != (unsigned char) ~0)
+		  {
+		    clear_padding = true;
+		    break;
+		  }
+	    }
+	  tree inttype = NULL_TREE;
+	  if (!clear_padding && tree_fits_uhwi_p (TYPE_SIZE (cmptype)))
+	    {
+	      HOST_WIDE_INT prec = tree_to_uhwi (TYPE_SIZE (cmptype));
+	      inttype = c_common_type_for_size (prec, 1);
+	      if (inttype
+		  && (!tree_int_cst_equal (TYPE_SIZE (cmptype),
+					   TYPE_SIZE (inttype))
+		      || TYPE_PRECISION (inttype) != prec))
+		inttype = NULL_TREE;
+	    }
+	  if (inttype)
+	    {
+	      TREE_OPERAND (rhs1, 0)
+		= build1_loc (loc, VIEW_CONVERT_EXPR, inttype,
+			      TREE_OPERAND (rhs1, 0));
+	      TREE_OPERAND (rhs1, 1)
+		= build1_loc (loc, VIEW_CONVERT_EXPR, inttype,
+			      TREE_OPERAND (rhs1, 1));
+	    }
+	  else
+	    {
+	      tree pcmptype = build_pointer_type (cmptype);
+	      tree tmp1 = create_tmp_var_raw (cmptype);
+	      TREE_ADDRESSABLE (tmp1) = 1;
+	      DECL_CONTEXT (tmp1) = current_function_decl;
+	      tmp1 = build4 (TARGET_EXPR, cmptype, tmp1,
+			     TREE_OPERAND (rhs1, 0), NULL, NULL);
+	      tmp1 = build1 (ADDR_EXPR, pcmptype, tmp1);
+	      tree tmp2 = create_tmp_var_raw (cmptype);
+	      TREE_ADDRESSABLE (tmp2) = 1;
+	      DECL_CONTEXT (tmp2) = current_function_decl;
+	      tmp2 = build4 (TARGET_EXPR, cmptype, tmp2,
+			     TREE_OPERAND (rhs1, 1), NULL, NULL);
+	      tmp2 = build1 (ADDR_EXPR, pcmptype, tmp2);
+	      tree fndecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
+	      rhs1 = build_call_expr_loc (loc, fndecl, 3, tmp1, tmp2,
+					  TYPE_SIZE_UNIT (cmptype));
+	      rhs1 = build2 (EQ_EXPR, boolean_type_node, rhs1,
+			     integer_zero_node);
+	      if (clear_padding)
+		{
+		  fndecl = builtin_decl_explicit (BUILT_IN_CLEAR_PADDING);
+		  tree cp1 = build_call_expr_loc (loc, fndecl, 1, tmp1);
+		  tree cp2 = build_call_expr_loc (loc, fndecl, 1, tmp2);
+		  rhs1 = omit_two_operands_loc (loc, boolean_type_node,
+						rhs1, cp2, cp1);
+		}
+	    }
+	}
+      if (r)
+	{
+	  tree var = create_tmp_var (boolean_type_node);
+	  DECL_CONTEXT (var) = current_function_decl;
+	  rtmp = build4 (TARGET_EXPR, boolean_type_node, var,
+			 NULL, NULL, NULL);
+	  save = in_late_binary_op;
+	  in_late_binary_op = true;
+	  x = build_modify_expr (loc, var, NULL_TREE, NOP_EXPR,
+				 loc, rhs1, NULL_TREE);
+	  in_late_binary_op = save;
+	  if (x == error_mark_node)
+	    return error_mark_node;
+	  gcc_assert (TREE_CODE (x) == MODIFY_EXPR
+		      && TREE_OPERAND (x, 0) == var);
+	  TREE_OPERAND (x, 0) = rtmp;
+	  rhs1 = omit_one_operand_loc (loc, boolean_type_node, x, rtmp);
+	}
+      rhs = build3_loc (loc, COND_EXPR, type, rhs1, rhs, new_lhs);
+      rhs1 = NULL_TREE;
+    }
 
   /* Punt the actual generation of atomic operations to common code.  */
   if (code == OMP_ATOMIC)
@@ -350,6 +471,7 @@ c_finish_omp_atomic (location_t loc, enum tree_code code,
   x = build2 (code, type, addr, rhs);
   SET_EXPR_LOCATION (x, loc);
   OMP_ATOMIC_MEMORY_ORDER (x) = memory_order;
+  OMP_ATOMIC_WEAK (x) = weak;
 
   /* Generally it is hard to prove lhs1 and lhs are the same memory
      location, just diagnose different variables.  */
@@ -412,8 +534,25 @@ c_finish_omp_atomic (location_t loc, enum tree_code code,
 			  bitsize_int (bitsize), bitsize_int (bitpos));
 	  type = TREE_TYPE (blhs);
 	}
-      x = build_modify_expr (loc, v, NULL_TREE, NOP_EXPR,
+      if (r)
+	{
+	  vtmp = create_tmp_var (TREE_TYPE (x));
+	  DECL_CONTEXT (vtmp) = current_function_decl;
+	}
+      else
+	vtmp = v;
+      x = build_modify_expr (loc, vtmp, NULL_TREE, NOP_EXPR,
 			     loc, x, NULL_TREE);
+      if (x == error_mark_node)
+	return error_mark_node;
+      if (r)
+	{
+	  vtmp = build4 (TARGET_EXPR, boolean_type_node, vtmp,
+			 NULL, NULL, NULL);
+	  gcc_assert (TREE_CODE (x) == MODIFY_EXPR
+		      && TREE_OPERAND (x, 0) == TARGET_EXPR_SLOT (vtmp));
+	  TREE_OPERAND (x, 0) = vtmp;
+	}
       if (rhs1 && rhs1 != orig_lhs)
 	{
 	  tree rhs1addr = build_unary_op (loc, ADDR_EXPR, rhs1, false);
@@ -446,6 +585,28 @@ c_finish_omp_atomic (location_t loc, enum tree_code code,
 
   if (pre)
     x = omit_one_operand_loc (loc, type, x, pre);
+  if (r && r != void_list_node)
+    {
+      in_late_binary_op = true;
+      tree x2 = build_modify_expr (loc, r, NULL_TREE, NOP_EXPR,
+				   loc, rtmp, NULL_TREE);
+      in_late_binary_op = save;
+      if (x2 == error_mark_node)
+	return error_mark_node;
+      x = omit_one_operand_loc (loc, TREE_TYPE (x2), x2, x);
+    }
+  if (v && vtmp != v)
+    {
+      in_late_binary_op = true;
+      tree x2 = build_modify_expr (loc, v, NULL_TREE, NOP_EXPR,
+				   loc, vtmp, NULL_TREE);
+      in_late_binary_op = save;
+      if (x2 == error_mark_node)
+	return error_mark_node;
+      x2 = build3_loc (loc, COND_EXPR, void_type_node, rtmp,
+		       void_node, x2);
+      x = omit_one_operand_loc (loc, TREE_TYPE (x2), x2, x);
+    }
   return x;
 }