Add __builtin_speculation_safe_value

This patch defines a new intrinsic function
__builtin_speculation_safe_value.  A generic default implementation is
defined which will attempt to use the backend pattern
"speculation_safe_barrier".  If this pattern is not defined, or if it
is not available, then the compiler will emit a warning, but
compilation will continue.

Note that the test spec-barrier-1.c will currently fail on all
targets.  This is deliberate, the failure will go away when
appropriate action is taken for each target backend.

gcc:
	* builtin-types.def (BT_FN_PTR_PTR_VAR): New function type.
	(BT_FN_I1_I1_VAR, BT_FN_I2_I2_VAR, BT_FN_I4_I4_VAR): Likewise.
	(BT_FN_I8_I8_VAR, BT_FN_I16_I16_VAR): Likewise.
	* builtin-attrs.def (ATTR_NOVOPS_NOTHROW_LEAF_LIST): New attribute
	list.
	* builtins.def (BUILT_IN_SPECULATION_SAFE_VALUE_N): New builtin.
	(BUILT_IN_SPECULATION_SAFE_VALUE_PTR): New internal builtin.
	(BUILT_IN_SPECULATION_SAFE_VALUE_1): Likewise.
	(BUILT_IN_SPECULATION_SAFE_VALUE_2): Likewise.
	(BUILT_IN_SPECULATION_SAFE_VALUE_4): Likewise.
	(BUILT_IN_SPECULATION_SAFE_VALUE_8): Likewise.
	(BUILT_IN_SPECULATION_SAFE_VALUE_16): Likewise.
	* builtins.c (expand_speculation_safe_value): New function.
	(expand_builtin): Call it.
	* doc/cpp.texi: Document predefine __HAVE_SPECULATION_SAFE_VALUE.
	* doc/extend.texi: Document __builtin_speculation_safe_value.
	* doc/md.texi: Document "speculation_barrier" pattern.
	* doc/tm.texi.in: Pull in TARGET_SPECULATION_SAFE_VALUE and
	TARGET_HAVE_SPECULATION_SAFE_VALUE.
	* doc/tm.texi: Regenerated.
	* target.def (have_speculation_safe_value, speculation_safe_value): New
	hooks.
	* targhooks.c (default_have_speculation_safe_value): New function.
	(default_speculation_safe_value): New function.
	* targhooks.h (default_have_speculation_safe_value): Add prototype.
	(default_speculation_safe_value): Add prototype.

c-family:
	* c-common.c (speculation_safe_resolve_call): New function.
	(speculation_safe_resolve_params): New function.
	(speculation_safe_resolve_return): New function.
	(resolve_overloaded_builtin): Handle __builtin_speculation_safe_value.
	* c-cppbuiltin.c (c_cpp_builtins): Add pre-define for
	__HAVE_SPECULATION_SAFE_VALUE.

testsuite:
	* c-c++-common/spec-barrier-1.c: New test.
	* c-c++-common/spec-barrier-2.c: New test.
	* gcc.dg/spec-barrier-3.c: New test.

From-SVN: r263168

1 files changed, 60 insertions, 0 deletions

diff --git a/gcc/builtins.c b/gcc/builtins.c
index c659611..39611de 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -6918,6 +6918,55 @@ inline_expand_builtin_string_cmp (tree exp, rtx target)
 			    const_str_n, mode);
 }
 
+/* Expand a call to __builtin_speculation_safe_value_<N>.  MODE
+   represents the size of the first argument to that call, or VOIDmode
+   if the argument is a pointer.  IGNORE will be true if the result
+   isn't used.  */
+static rtx
+expand_speculation_safe_value (machine_mode mode, tree exp, rtx target,
+			       bool ignore)
+{
+  rtx val, failsafe;
+  unsigned nargs = call_expr_nargs (exp);
+
+  tree arg0 = CALL_EXPR_ARG (exp, 0);
+
+  if (mode == VOIDmode)
+    {
+      mode = TYPE_MODE (TREE_TYPE (arg0));
+      gcc_assert (GET_MODE_CLASS (mode) == MODE_INT);
+    }
+
+  val = expand_expr (arg0, NULL_RTX, mode, EXPAND_NORMAL);
+
+  /* An optional second argument can be used as a failsafe value on
+     some machines.  If it isn't present, then the failsafe value is
+     assumed to be 0.  */
+  if (nargs > 1)
+    {
+      tree arg1 = CALL_EXPR_ARG (exp, 1);
+      failsafe = expand_expr (arg1, NULL_RTX, mode, EXPAND_NORMAL);
+    }
+  else
+    failsafe = const0_rtx;
+
+  /* If the result isn't used, the behavior is undefined.  It would be
+     nice to emit a warning here, but path splitting means this might
+     happen with legitimate code.  So simply drop the builtin
+     expansion in that case; we've handled any side-effects above.  */
+  if (ignore)
+    return const0_rtx;
+
+  /* If we don't have a suitable target, create one to hold the result.  */
+  if (target == NULL || GET_MODE (target) != mode)
+    target = gen_reg_rtx (mode);
+
+  if (GET_MODE (val) != mode && GET_MODE (val) != VOIDmode)
+    val = convert_modes (mode, VOIDmode, val, false);
+
+  return targetm.speculation_safe_value (mode, target, val, failsafe);
+}
+
 /* Expand an expression EXP that calls a built-in function,
    with result going to TARGET if that's convenient
    (and in mode MODE if that's convenient).
@@ -8029,6 +8078,17 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
     case BUILT_IN_GOACC_PARLEVEL_SIZE:
       return expand_builtin_goacc_parlevel_id_size (exp, target, ignore);
 
+    case BUILT_IN_SPECULATION_SAFE_VALUE_PTR:
+      return expand_speculation_safe_value (VOIDmode, exp, target, ignore);
+
+    case BUILT_IN_SPECULATION_SAFE_VALUE_1:
+    case BUILT_IN_SPECULATION_SAFE_VALUE_2:
+    case BUILT_IN_SPECULATION_SAFE_VALUE_4:
+    case BUILT_IN_SPECULATION_SAFE_VALUE_8:
+    case BUILT_IN_SPECULATION_SAFE_VALUE_16:
+      mode = get_builtin_sync_mode (fcode - BUILT_IN_SPECULATION_SAFE_VALUE_1);
+      return expand_speculation_safe_value (mode, exp, target, ignore);
+
     default:	/* just do library call, if unknown builtin */
       break;
     }