aarch64: Add GCS builtins

Add new builtins for GCS:

  void *__builtin_aarch64_gcspr (void)
  uint64_t __builtin_aarch64_gcspopm (void)
  void *__builtin_aarch64_gcsss (void *)

The builtins are always enabled, but should be used behind runtime
checks in case the target does not support GCS. They are thin
wrappers around the corresponding instructions.

The GCS pointer is modelled with void * type (normal stores do not
work on GCS memory, but it is writable via the gcsss operation or
via GCSSTR if enabled so not const) and an entry on the GCS is
modelled with uint64_t (since it has fixed size and can be a token
that's not a pointer).

gcc/ChangeLog:

	* config/aarch64/aarch64-builtins.cc (enum aarch64_builtins): Add
	AARCH64_BUILTIN_GCSPR, AARCH64_BUILTIN_GCSPOPM, AARCH64_BUILTIN_GCSSS.
	(aarch64_init_gcs_builtins): New.
	(aarch64_general_init_builtins): Call aarch64_init_gcs_builtins.
	(aarch64_expand_gcs_builtin): New.
	(aarch64_general_expand_builtin): Call aarch64_expand_gcs_builtin.

Co-authored-by: Richard Sandiford <richard.sandiford@arm.com>

diff --git a/gcc/config/aarch64/aarch64-builtins.cc b/gcc/config/aarch64/aarch64-builtins.cc
index e693a14f4f3c3b6faef7b898a07dd493a8469ad7..b860e22f01f41a832c26c165a9eca6e81efced71 100644 (file)
--- a/gcc/config/aarch64/aarch64-builtins.cc
+++ b/gcc/config/aarch64/aarch64-builtins.cc
@@ -878,6 +878,9 @@ enum aarch64_builtins
   AARCH64_PLIX,
   /* Armv8.9-A / Armv9.4-A builtins.  */
   AARCH64_BUILTIN_CHKFEAT,
+  AARCH64_BUILTIN_GCSPR,
+  AARCH64_BUILTIN_GCSPOPM,
+  AARCH64_BUILTIN_GCSSS,
   AARCH64_BUILTIN_MAX
 };
 
@@ -2240,6 +2243,29 @@ aarch64_init_fpsr_fpcr_builtins (void)
                                   AARCH64_BUILTIN_SET_FPSR64);
 }
 
+/* Add builtins for Guarded Control Stack instructions.  */
+
+static void
+aarch64_init_gcs_builtins (void)
+{
+  tree ftype;
+
+  ftype = build_function_type_list (ptr_type_node, NULL);
+  aarch64_builtin_decls[AARCH64_BUILTIN_GCSPR]
+    = aarch64_general_add_builtin ("__builtin_aarch64_gcspr", ftype,
+                                  AARCH64_BUILTIN_GCSPR);
+
+  ftype = build_function_type_list (uint64_type_node, NULL);
+  aarch64_builtin_decls[AARCH64_BUILTIN_GCSPOPM]
+    = aarch64_general_add_builtin ("__builtin_aarch64_gcspopm", ftype,
+                                  AARCH64_BUILTIN_GCSPOPM);
+
+  ftype = build_function_type_list (ptr_type_node, ptr_type_node, NULL);
+  aarch64_builtin_decls[AARCH64_BUILTIN_GCSSS]
+    = aarch64_general_add_builtin ("__builtin_aarch64_gcsss", ftype,
+                                  AARCH64_BUILTIN_GCSSS);
+}
+
 /* Initialize all builtins in the AARCH64_BUILTIN_GENERAL group.  */
 
 void
@@ -2287,6 +2313,8 @@ aarch64_general_init_builtins (void)
     = aarch64_general_add_builtin ("__builtin_aarch64_chkfeat", ftype_chkfeat,
                                   AARCH64_BUILTIN_CHKFEAT);
 
+  aarch64_init_gcs_builtins ();
+
   if (in_lto_p)
     handle_arm_acle_h ();
 }
@@ -3381,6 +3409,48 @@ aarch64_expand_fpsr_fpcr_getter (enum insn_code icode, machine_mode mode,
   return op.value;
 }
 
+/* Expand GCS builtin EXP with code FCODE, putting the result
+   into TARGET.  If IGNORE is true the return value is ignored.  */
+
+rtx
+aarch64_expand_gcs_builtin (tree exp, rtx target, int fcode, int ignore)
+{
+  if (fcode == AARCH64_BUILTIN_GCSPR)
+    {
+      expand_operand op;
+      create_output_operand (&op, target, DImode);
+      expand_insn (CODE_FOR_aarch64_load_gcspr, 1, &op);
+      return op.value;
+    }
+  if (fcode == AARCH64_BUILTIN_GCSPOPM && ignore)
+    {
+      expand_insn (CODE_FOR_aarch64_gcspopm_xzr, 0, 0);
+      return target;
+    }
+  if (fcode == AARCH64_BUILTIN_GCSPOPM)
+    {
+      expand_operand ops[2];
+      create_output_operand (&ops[0], target, DImode);
+      create_input_operand (&ops[1], const0_rtx, DImode);
+      expand_insn (CODE_FOR_aarch64_gcspopm, 2, ops);
+      return gen_lowpart (ptr_mode, ops[0].value);
+    }
+  if (fcode == AARCH64_BUILTIN_GCSSS)
+    {
+      expand_operand opnd;
+      rtx arg = expand_normal (CALL_EXPR_ARG (exp, 0));
+      arg = convert_modes (DImode, ptr_mode, arg, true);
+      create_input_operand (&opnd, arg, DImode);
+      expand_insn (CODE_FOR_aarch64_gcsss1, 1, &opnd);
+      expand_operand ops[2];
+      create_output_operand (&ops[0], target, DImode);
+      create_input_operand (&ops[1], const0_rtx, DImode);
+      expand_insn (CODE_FOR_aarch64_gcsss2, 2, ops);
+      return gen_lowpart (ptr_mode, ops[0].value);
+    }
+  gcc_unreachable ();
+}
+
 /* Expand an expression EXP that calls built-in function FCODE,
    with result going to TARGET if that's convenient.  IGNORE is true
    if the result of the builtin is ignored.  */
@@ -3515,6 +3585,11 @@ aarch64_general_expand_builtin (unsigned int fcode, tree exp, rtx target,
        expand_insn (CODE_FOR_aarch64_chkfeat, 0, 0);
        return copy_to_reg (x16_reg);
       }
+
+    case AARCH64_BUILTIN_GCSPR:
+    case AARCH64_BUILTIN_GCSPOPM:
+    case AARCH64_BUILTIN_GCSSS:
+      return aarch64_expand_gcs_builtin (exp, target, fcode, ignore);
     }
 
   if (fcode >= AARCH64_SIMD_BUILTIN_BASE && fcode <= AARCH64_SIMD_BUILTIN_MAX)