Merge pull request gcc-mirror#29 from iains/contracts-nonattr-p1494r4

Contracts nonattr p1494r4

gcc/builtins.cc

@@ -8341,6 +8341,10 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
       expand_builtin_unreachable ();
       return const0_rtx;
 
+    case BUILT_IN_OBSERVABLE:
+      /* Emits no code.  */
+      return const0_rtx;
+
     CASE_FLT_FN (BUILT_IN_SIGNBIT):
     case BUILT_IN_SIGNBITD32:
     case BUILT_IN_SIGNBITD64:

gcc/builtins.def

@@ -1071,6 +1071,7 @@ DEF_LIB_BUILTIN        (BUILT_IN_STRFTIME, "strftime", BT_FN_SIZE_STRING_SIZE_CO
 DEF_GCC_BUILTIN        (BUILT_IN_TRAP, "trap", BT_FN_VOID, ATTR_NORETURN_NOTHROW_LEAF_COLD_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_UNREACHABLE_TRAP, "unreachable trap", BT_FN_VOID, ATTR_CONST_NORETURN_NOTHROW_LEAF_COLD_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_UNREACHABLE, "unreachable", BT_FN_VOID, ATTR_CONST_NORETURN_NOTHROW_LEAF_COLD_LIST)
+DEF_GCC_BUILTIN        (BUILT_IN_OBSERVABLE, "observable", BT_FN_VOID, ATTR_NOTHROW_LEAF_LIST)
 DEF_GCC_BUILTIN        (BUILT_IN_UNWIND_INIT, "unwind_init", BT_FN_VOID, ATTR_NULL)
 DEF_GCC_BUILTIN        (BUILT_IN_UPDATE_SETJMP_BUF, "update_setjmp_buf", BT_FN_VOID_PTR, ATTR_NULL)
 DEF_GCC_BUILTIN        (BUILT_IN_VA_COPY, "va_copy", BT_FN_VOID_VALIST_REF_VALIST_ARG, ATTR_NOTHROW_LEAF_LIST)

gcc/c-family/c-common.cc

@@ -432,6 +432,7 @@ const struct c_common_resword c_common_reswords[] =
   { "__builtin_convertvector", RID_BUILTIN_CONVERTVECTOR, 0 },
   { "__builtin_has_attribute", RID_BUILTIN_HAS_ATTRIBUTE, 0 },
   { "__builtin_launder", RID_BUILTIN_LAUNDER, D_CXXONLY },
+  { "__builtin_observable", RID_BUILTIN_OBSERVABLE, D_CXXONLY },
   { "__builtin_shuffle", RID_BUILTIN_SHUFFLE, 0 },
   { "__builtin_shufflevector", RID_BUILTIN_SHUFFLEVECTOR, 0 },
   { "__builtin_stdc_bit_ceil", RID_BUILTIN_STDC, D_CONLY },

gcc/c-family/c-common.h

@@ -166,6 +166,7 @@ enum rid
   /* C++ extensions */
   RID_ADDRESSOF,
   RID_BUILTIN_LAUNDER,
+  RID_BUILTIN_OBSERVABLE,
   RID_BUILTIN_BIT_CAST,
 
   /* C++11 */

gcc/c-family/c.opt

@@ -1844,6 +1844,10 @@ fcontract-disable-optimized-checks
 C++ Var(flag_contract_disable_optimized_checks) Init(0)
 -fcontract-disable-optimized-checks	Disable optimisation of contract checks.
 
+fcontract-disable-check-epochs
+C++ Var(flag_contract_disable_check_epochs) Init(0)
+-fcontract-disable-epoch-checks	Disable insertion of epoch markers after each contract check.
+
 fcoroutines
 C++ LTO Var(flag_coroutines)
 Enable C++ coroutines (experimental).

gcc/cp/constexpr.cc

@@ -1602,6 +1602,10 @@ cxx_eval_builtin_function_call (const constexpr_ctx *ctx, tree t, tree fun,
 	/* These builtins shall be ignored during constant expression
 	   evaluation.  */
 	return void_node;
+      case BUILT_IN_OBSERVABLE:
+	if (ctx->manifestly_const_eval == mce_true)
+	  return void_node;
+	/* FALLTHROUGH */
       case BUILT_IN_UNREACHABLE:
       case BUILT_IN_TRAP:
 	if (!*non_constant_p && !ctx->quiet)

gcc/cp/contracts.cc

@@ -2101,13 +2101,17 @@ build_contract_check (tree contract)
 
 /* Add the contract statement CONTRACT to the current block if valid.  */
 
-static void
+static bool
 emit_contract_statement (tree contract)
 {
   /* Only add valid contracts.  */
-  if (get_contract_semantic (contract) != CCS_INVALID
-      && CONTRACT_CONDITION (contract) != error_mark_node)
-    add_stmt (contract);
+  if (contract == error_mark_node
+      || CONTRACT_CONDITION (contract) == error_mark_node
+      || get_contract_semantic (contract) == CCS_INVALID)
+    return false;
+
+  add_stmt (contract);
+  return true;
 }
 
 /* Generate the statement for the given contract attribute by adding the
@@ -2180,7 +2184,15 @@ remap_and_emit_conditions (tree fn, tree condfn, tree_code code)
 	{
 	  contract = copy_node (contract);
 	  remap_contract (fn, condfn, contract, /*duplicate_p=*/false);
-	  emit_contract_statement (contract);
+	  if (!emit_contract_statement (contract))
+	    continue;
+	  if (flag_contract_disable_check_epochs)
+	    continue;
+	  /* Insert a std::observable () epoch marker.  */
+	  tree fn = builtin_decl_explicit (BUILT_IN_OBSERVABLE);
+	  releasing_vec vec;
+	  fn = finish_call_expr (fn, &vec, false, false, tf_warning_or_error);
+	  finish_expr_stmt (fn);
 	}
     }
 }

gcc/cp/cp-objcp-common.cc

@@ -583,6 +583,7 @@ names_builtin_p (const char *name)
     case RID_BUILTIN_SHUFFLE:
     case RID_BUILTIN_SHUFFLEVECTOR:
     case RID_BUILTIN_LAUNDER:
+    case RID_BUILTIN_OBSERVABLE:
     case RID_BUILTIN_ASSOC_BARRIER:
     case RID_BUILTIN_BIT_CAST:
     case RID_OFFSETOF:

gcc/cp/cxxapi-data.csv

@@ -1105,6 +1105,7 @@
 <cstdint>,uintptr_t,1,cxx11
 # <cstdio> TODO
 # <cstdlib> TODO
+<cstdlib>,observable,1,cxx11
 # <cstring> TODO
 # <ctime> TODO
 # <cuchar> TODO

gcc/cp/parser.cc

@@ -7726,6 +7726,7 @@ cp_parser_postfix_expression (cp_parser *parser, bool address_p, bool cast_p,
     case RID_BUILTIN_SHUFFLE:
     case RID_BUILTIN_SHUFFLEVECTOR:
     case RID_BUILTIN_LAUNDER:
+    case RID_BUILTIN_OBSERVABLE:
     case RID_BUILTIN_ASSOC_BARRIER:
       {
 	vec<tree, va_gc> *vec;
@@ -7769,6 +7770,22 @@ cp_parser_postfix_expression (cp_parser *parser, bool address_p, bool cast_p,
 	      }
 	    break;
 
+	  case RID_BUILTIN_OBSERVABLE:
+	    if (vec->length () == 0)
+	      {
+		tree fn = builtin_decl_explicit (BUILT_IN_OBSERVABLE);
+		releasing_vec vec;
+		postfix_expression = finish_call_expr (fn, &vec, false, false,
+						       tf_warning_or_error);
+	      }
+	    else
+	      {
+		error_at (loc, "%<__builtin_observable%> does not take"
+			  " arguments");
+		postfix_expression = error_mark_node;
+	      }
+	    break;
+
 	  case RID_BUILTIN_ASSOC_BARRIER:
 	    if (vec->length () == 1)
 	      postfix_expression = build1_loc (loc, PAREN_EXPR,

gcc/cp/std-name-hint.gperf

@@ -118,6 +118,8 @@ uint_least64_t, "<cstdint>", cxx11
 uint_least8_t, "<cstdint>", cxx11
 uintmax_t, "<cstdint>", cxx11
 uintptr_t, "<cstdint>", cxx11
+# <cstdlib>
+observable, "<cstdlib>", cxx11
 # <deque>
 deque, "<deque>", cxx98
 # <exception>